**Generation of Biohydrogen by Anaerobic Fermentation of Organics Wastes in Colombia**

Edilson León Moreno Cárdenas, Deisy Juliana Cano Quintero and Cortés Marín Elkin Alonso

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53351

**1. Introduction**

#### **1.1. The trouble of organics solids wastes**

In the protection of environment, the adequate handling of solids wastes occupy a main place, the integral handling of wastes is a term applied to all activities associated with the wastes management in the society. The main aim is the administration of wastes associated with the environment and public health. The handling of solid wastes is one of the main environmental problems in the cities due to its generations increase simultaneously with the growth of the cities, its industrialization and the increase of population. In addition, the actual life style carries out a high demand of consumption of goods that generally are thrown out in a short time; this generates more production of wastes and therefor having to search for solutions to the final disposition.

A solution for the trouble of the urban solids wastes is the implementation of process of reusing and giving value to the different materials that form what is known as "garbage", with the purpose of obtaining products or sub products that can be to introduce into new economic cycles. The maximization of reusing and giving value to solids wastes carry out benefits as: less consumption of natural sources, reduction of energy consumption, less environmental pollution, better use of the location where the garbage is placed and economic benefits from recovered materials. So the changes of consumption patron and the sustainable production are essential for the reduction of wastes production.

© 2013 Cárdenas et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Cárdenas et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Is very difficult to stop the production of solids wastes, the idea is consider the solids wastes as a source of material reusable, raw matter, organics nutrients, biofuels and energetics fuel. The set of process to recover and treatment the wastes are known as valorization of solids wastes. This production of wastes is due to origin, social context and production activities [1]. During the valorization and reusing of wastes, is necessary take account aspect as recollection and transport, with this is possible to obtain highs benefices by the transformation. Addition‐ ally is necessary to include applications of new concepts related to the financial services, decentralized management, community contribution and the options of transformation, valorization and incorporation to economic cycles [2].

country, the management of wastes is focused to the final disposal in landfill; only 2,4% is

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**Disposing of wastes tons/day Participation (%) Municipalities** Landfill 22.204 88,5 653 Open dumpsite 2.185 8,7 297 Treatment facility 615 2,4 98 Buried 75 0,3 19

Discharged into rivers <0,1 10 Incineration <0,1 11 Total 25.076 100 1.088

In the country, the solid wastes are mainly composed of organic material (65%), followed by the plastics (14%), paper and cardboard (5%), glass (4%), other components with minor

In Colombia the major quantity of solid wastes generated are collected and treated by municipal companies (waste from domestic activities, commercials and industrials); however in some regions the problem of wastes solids is very important as the final disposition is made with little control, generating environmental pollution. The production of wastes (kg/habitant/ day) is approximately 0,5 kg/habitant/day, oscillating between 1 kg/habitant/day for the big

dedicated to recycle and valorization [1].

Source: [4].

participation.

Source: [2].

**Table 1.** Disposing of wastes in Colombia

**Table 2.** Composition of solids wastes in Colombia

#### **1.2. Source of wastes**

At the whole world, the solids wastes from different sources are generating negative environ‐ mental impact to the nature, the biodiversity and life in the planet. This is caused by the inappropriate disposition of wastes, the increase of population, the processes of industrial transformation, agroindustrial and life habits of people [3]. At the present time, one charac‐ teristic of the society is the increase unbridled of the production and accumulation of solids wastes, which are generated without a solution to its final disposition. In the most of cases, this produced an inappropriate final disposition, an increase in the environment deterioration (air, surface water and groundwater, soil, landscape), problems in the public health and personal security [2].

The characteristics of solids wastes changed in function of the main activity (industry, trade, tourism and others), the habits of the population, type of fed, consumption models, environ‐ ment conditions and others. The solids wastes can be classified according to: the source (domestic activities, institutional, commercial, industry, farming, municipal services and construction); the constitution (recyclable material and non-recyclable) and grade of danger (commons and dangerous).

The present chapter shows the energetic potential of the solid organic wastes generated in Colombia and its capacity to produce biohydrogen by anaerobic fermentation; additionally is presented a research carried out at the Laboratory of Agricultural Mechanization of the National University of Colombia in Medellín between the years 2009 and 2012, which main aim was determinate the initial feasibility to generate biohydrogen from urban organics wastes and to establish some conditions to operate a bioreactor type batch.

#### **2. Generation of solids wastes in Colombia**

The quantity of wastes produced depend of factors as: the number of inhabitant in the city, urbanization rate, consumption habits, cultural practices to handle of wastes, the income, the application of technology and industrial development. According to the information reported by the "Superintendencia de Servicios Públicos Domiciliarios" by 2008, see [4], in Colombia were generated daily 25.079 tons of urban solids wastes, 10 million of tons/year, which 77% were domestics (19.310,8 ton); 15% Industrials (3.761,9) and 8% others (2.006,3 ton). In the country, the management of wastes is focused to the final disposal in landfill; only 2,4% is dedicated to recycle and valorization [1].


**Table 1.** Disposing of wastes in Colombia

In the country, the solid wastes are mainly composed of organic material (65%), followed by the plastics (14%), paper and cardboard (5%), glass (4%), other components with minor participation.

Source: [2].

**Table 2.** Composition of solids wastes in Colombia

In Colombia the major quantity of solid wastes generated are collected and treated by municipal companies (waste from domestic activities, commercials and industrials); however in some regions the problem of wastes solids is very important as the final disposition is made with little control, generating environmental pollution. The production of wastes (kg/habitant/ day) is approximately 0,5 kg/habitant/day, oscillating between 1 kg/habitant/day for the big dedicated to recycle and valorization [1].

Table 1. Disposing of wastes in Colombia

cardboard (5%), glass (4%), other components with minor participation.

Source: [4].

Source: [2].

cities until 0,2 kg/habitant/day in the small towns [5]. The "Superintendencia de Servicios Públicos Domiciliarios" published by 2002 a study about the final disposition of the solids wastes in 1.086 cities. The technologies more frequent are: dumpsite and open incineration (52%), then landfill (30 %), and finally the use of composting, incineration and others (18%), [6]. In Colombia the major quantity of solid wastes generated are collected and treated by municipal companies (waste from domestic activities, commercials and industrials); however in some regions the problem of wastes solids is very important as the final disposition is made with little control, generating environmental pollution. The production of wastes (kg/habitant/day) is approximately 0,5 kg/habitant/day, oscillating between 1 kg/habitant/day for the big cities until 0,2 kg/habitant/day in the small towns [5]. The "Superintendencia de Servicios Públicos Domiciliarios" published by 2002 a study about the final disposition of the solids wastes in 1.086 cities. The technologies more frequent are: dumpsite and open incineration (52%), then landfill (30 %), and

The quantity of wastes produced depend of factors as: the number of inhabitant in the city, urbanization rate, consumption habits, cultural practices to handle of wastes, the income, the application of technology and industrial development. According to the information reported by the "Superintendencia de Servicios Públicos Domiciliarios" by 2008, see [4], in Colombia were generated daily 25.079 tons of urban solids wastes, 10 million of tons/year, which 77% were domestics (19.310,8 ton); 15% Industrials (3.761,9) and 8% others (2.006,3 ton). In the country, the management of wastes is focused to the final disposal in landfill; only 2,4% is

> **Disposing of wastes tons/day Participation (%) Municipalities**  Landfill 22.204 88,5 653 Open dumpsite 2.185 8,7 297 Treatment facility 615 2,4 98 Buried 75 0,3 19 Discharged into rivers <0,1 10 Incineration <0,1 11 Total 25.076 100 1.088

In the country, the solid wastes are mainly composed of organic material (65%), followed by the plastics (14%), paper and

**•** Decree 605 of 1996: Indications for an adequate cleaning service, from the generation,

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**•** Committee Technical ICONTEC 000019 about environmental management of solids wastes.

**•** Decree 1716 of August 2002 of "Ministerio de Desarrollo Económico" (In English: Economic Development Ministry) by mean the law 142 of 1994, law 632 of 2000 and the law 689 of 2001, related to the cleaning public service, the law 2811 of 1974 and the law 99 of 1993. The article 8 related to the program for the integral management of solids wastes, which should

The increase of energy demand in recent decades driven in particular by developed countries and countries with economic growth as Colombia, is leading to rapid depletion of nonrenew‐ able energy resources, increasing pollution and global warming. The alternatives energetics sources emerge as a great option to reduce the adverse effects of this development. The biomass is considered as the alternative energetic source the most potential, according to reports from the World Energy Council [11] it is estimated that energy from biomass will account for 25,4% of global consumption by 2030 and 80% by 2080. Biomass is very varied due to its production and origin, a particular type are the wastes of natural processes, industrial or agroindustrial. It is estimated that Colombia has an energy potential from residual biomass of 449.485 TJ / year, also has a land area of 114,174,800 hectares, of which 44,77% are engaged to agricultural activities, this places to sector as the main source of wastes (with an energy potential of 331.645 TJ / year, mainly from annual and permanent crops). At the second place are the wastes from livestock activities (with an energy potential of 117.747 TJ / year), then the urban organic wastes (wastes from food and homes with an energy potential of 91 TJ / year) and finally the wastes

Among the methods to profit energetically the residual biomass, the anaerobic fermentation is a way of great interest, with this bioprocess is possible to generate a gas with high energy characteristics such as hydrogen and sludge that could be employed as fertilizer on crop. The generation of biohydrogen by anaerobic fermentation of wastes has generated great interest in the last decades. Hydrogen is a promising option as energy source [13, 14], it is a clean renewable resource because its combustion produces only water as emissions, in addition has the highest energy content per unit mass, with a value of 122 kJ / g [13]. The biological production of hydrogen can be seen as a promising option [15], two types of bacteria are involved in the process: acidogenic bacteria which initially to reduce the substrate in H2 (biohydrogen), acetic acid and CO2 and the methanogenic bacteria that converted these elements in methane gas. If the purpose is to produce biohydrogen, favorable conditions for the growth of the first type of bacteria (acidogenic) should be provided, inhibiting or elimi‐ nating the population of methanogenic bacteria [16]. Currently there are two methods to inhibit

The residual biomass in Colombia has a high potential as alternative energetic source, only in wastes of sugar cane, rice husk, coco fiber, coffee pulp, oil palm, bean seed and barley, the

storage, collection, transport, to final disposition.

from agroindustrial activities [12].

be realized by the cities in a maximum time of 2 years [10].

this type of bacteria: thermal shock and acidification [17, 18].

**2.2. Organic solids wastes and its energetic potential in Colombia**

Figure 1. Final disposition of solids wastes in Colombian for 1.086 municipalities, 2002. Source: [6].

**Figure 1.** Final disposition of solids wastes in Colombian for 1.086 municipalities, 2002.

finally the use of composting, incineration and others (18%), [6].

There are two options to solve the problems generated by urban solid wastes which can be applied simultaneously to reach an optimum result:


The biomass in Colombia has calorific values between 4,384 kcal / kg for stems of coffee and 1,800 kcal / kg for banana rachis [7]. These values are comparable with reports from other countries as China where biomass from agricultural and forest activities have values between 3,827 to 4,784 kcal / kg [8]. In Argentina the lignocellulose biomass has values between 3,000 – 3,500 Kcal / kg and the municipal wastes between 2,000 and 2,500 Kcal / kg [9].

#### **2.1. Colombian normativity about solid wastes**

The Colombian normativity related to management of organics solids wastes began with the code of renewable natural sources (decree 2811 of 1974) and were implemented the followed norms:


#### **2.2. Organic solids wastes and its energetic potential in Colombia**

The increase of energy demand in recent decades driven in particular by developed countries and countries with economic growth as Colombia, is leading to rapid depletion of nonrenew‐ able energy resources, increasing pollution and global warming. The alternatives energetics sources emerge as a great option to reduce the adverse effects of this development. The biomass is considered as the alternative energetic source the most potential, according to reports from the World Energy Council [11] it is estimated that energy from biomass will account for 25,4% of global consumption by 2030 and 80% by 2080. Biomass is very varied due to its production and origin, a particular type are the wastes of natural processes, industrial or agroindustrial. It is estimated that Colombia has an energy potential from residual biomass of 449.485 TJ / year, also has a land area of 114,174,800 hectares, of which 44,77% are engaged to agricultural activities, this places to sector as the main source of wastes (with an energy potential of 331.645 TJ / year, mainly from annual and permanent crops). At the second place are the wastes from livestock activities (with an energy potential of 117.747 TJ / year), then the urban organic wastes (wastes from food and homes with an energy potential of 91 TJ / year) and finally the wastes from agroindustrial activities [12].

Among the methods to profit energetically the residual biomass, the anaerobic fermentation is a way of great interest, with this bioprocess is possible to generate a gas with high energy characteristics such as hydrogen and sludge that could be employed as fertilizer on crop. The generation of biohydrogen by anaerobic fermentation of wastes has generated great interest in the last decades. Hydrogen is a promising option as energy source [13, 14], it is a clean renewable resource because its combustion produces only water as emissions, in addition has the highest energy content per unit mass, with a value of 122 kJ / g [13]. The biological production of hydrogen can be seen as a promising option [15], two types of bacteria are involved in the process: acidogenic bacteria which initially to reduce the substrate in H2 (biohydrogen), acetic acid and CO2 and the methanogenic bacteria that converted these elements in methane gas. If the purpose is to produce biohydrogen, favorable conditions for the growth of the first type of bacteria (acidogenic) should be provided, inhibiting or elimi‐ nating the population of methanogenic bacteria [16]. Currently there are two methods to inhibit this type of bacteria: thermal shock and acidification [17, 18].

The residual biomass in Colombia has a high potential as alternative energetic source, only in wastes of sugar cane, rice husk, coco fiber, coffee pulp, oil palm, bean seed and barley, the potential is 12.000 MW/year approximately. The wastes are produced in different regions of the country and during all year. The country has a potential for generation of biomass of 331'638.720 ton/year, if all agricultural and urban wastes were treated by fermentation anaerobic, could be generated 28'825.609 m3 of biohydrogen, this might give a energetic potential of 144 GW, upper value to country potential in wind energy (21 GW), tidal energetic potential (30 GW with two coasts) and geothermic energetic potential (1 GW).

quia and was made a photographic register of solids wastes generated. The photographs were

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According to the information collected and the photographic register from the first phase, the wastes with greater production were selected to be introduced into a batch bioreactor.

The quantity of volatile solids,total solids andelemental composition on both wet anddry basis (coal, nitrogen and hydrogen) were obtained for each wastes. Were taken samples of 5 grams andtheanalysismethodappliedwas theWendeemethod(theanalysiswasmadeatthechemical analysis laboratory of National University in Medellin). With that information was calculated the quantity of wastes touse. Six samples of 3 grams in each wastes were taken in orderto obtain the elemental analysis, in this case the method applied was burn of sample and the equipment employed was an elemental analyzer CE – 440 (Figure 2a). The samples were triturated with a precision crusher – IKA WERNE with sieve of 0,5 mm (Figure 2b) and then were dried in a lyophilizer LABCONCO Freezone 12L (Figure 2c). In order to determine the quantity of wastes and water to be employed, 6 grams of volatile solids per liter-day were used as organics load

**Figure 2.** Elemental analyzer CE – 440 (a), Crusher MF Basic- IKA WERKE (b), Lyophilizer LABCONCO - Freezone 12L (c).

A batch bioreactor of 2000 liters was installed, the wastes were triturated to facilitate its access into bioreactor and its process by the bacteria. The quantity of gas generated was registered with a gas flow meter Metrex G 2,5 with accurate of 0,040 m³/h; maximum pressure of 40 kPa, additionally was employed a gel of silica to remove the wet of gas. The load of bioreactor was made during four days, each day was used the same quantity until to complete the total load.

The relativity humidity and environment temperature were registered daily, was used a thermohygrometer with rank in temperature until 120°C and 100% in relativity humidity (Figure 4). The pH into the bioreactor was registered daily too, in this case was employed a digital pH-meter Hanna Instruments, with accurate of ± 0,2 (reference temperature of 20°C).

taken twice per day at the morning and afternoon. **Phase 2.** Selection of wastes with greater production

**Phase 4.** Installation of bioreactor

**Phase 5.** Principal variables to register

**Phase 3.** Elemental Composition and chemical composition analysis

[19], additionally was employed a concentration on volatile solids of 5% [20].

In Colombia this quantity of biohydrogen could replace all diesel requested by the diesel electrical plants installed in the country. This has a great important especially in regions without connection to national electrical grid. In the country approximately the 66% of the territory are not connection to national electrical grid, this is 1,4 millions of people, namely the 4% of the population. The country has an installed electric capacity at the region without connection to national electrical grid of 102 MW of which 97 MW are produced by diesel plants, this quantity could be generated, using only the 40% of the urban organic wastes generated at the country. Colombia produces 250.000 tons/year of banana wastes with a potential to generated 100.000 m3 of biohydrogen by anaerobic fermentation, this represent 500 MW of energy per year, quantity enough to supply the electric energy demand of 200.000 people during a year.

### **3. Generation of biohydrogen in Colombia**

A research in order to determine the initial feasibility to generate biohydrogen from urban organics wastes and then established some conditions to operate a batch bioreactor was developed in Colombia. This section presents the results of this research and analysis the potential use of urban wastes as sources to generate hydrogen.

#### **3.1. Localization**

The research was performance between the years 2009 and 2012, at the Laboratory of Agri‐ cultural Mechanization of the National University of Colombia in Medellín, localized in 6°13′55″N and 75°34′05″W, with average annual temperature of 24°C, relative humidity of 88% and average annual precipitation of 1571mm.

#### **3.2. Methods**

Two stages were established to develop the research, the first had five phases.

#### *3.2.1. First stage*

**Phase 1.** Identification of organic wastes generated at the Central Wholesaler of Antioquia

The Central Wholesaler of Antioquia is the main company dedicated to trade food in the city of Medellín (fruits, vegetable and some grains). At the first phase historical information related to organic wastes production during two year was supplied by Central Wholesaler of Antio‐ quia and was made a photographic register of solids wastes generated. The photographs were taken twice per day at the morning and afternoon.

**Phase 2.** Selection of wastes with greater production

According to the information collected and the photographic register from the first phase, the wastes with greater production were selected to be introduced into a batch bioreactor.

**Phase 3.** Elemental Composition and chemical composition analysis

The quantity of volatile solids,total solids andelemental composition on both wet anddry basis (coal, nitrogen and hydrogen) were obtained for each wastes. Were taken samples of 5 grams andtheanalysismethodappliedwas theWendeemethod(theanalysiswasmadeatthechemical analysis laboratory of National University in Medellin). With that information was calculated the quantity of wastes touse. Six samples of 3 grams in each wastes were taken in orderto obtain the elemental analysis, in this case the method applied was burn of sample and the equipment employed was an elemental analyzer CE – 440 (Figure 2a). The samples were triturated with a precision crusher – IKA WERNE with sieve of 0,5 mm (Figure 2b) and then were dried in a lyophilizer LABCONCO Freezone 12L (Figure 2c). In order to determine the quantity of wastes and water to be employed, 6 grams of volatile solids per liter-day were used as organics load [19], additionally was employed a concentration on volatile solids of 5% [20].

**Figure 2.** Elemental analyzer CE – 440 (a), Crusher MF Basic- IKA WERKE (b), Lyophilizer LABCONCO - Freezone 12L (c).

#### **Phase 4.** Installation of bioreactor

A batch bioreactor of 2000 liters was installed, the wastes were triturated to facilitate its access into bioreactor and its process by the bacteria. The quantity of gas generated was registered with a gas flow meter Metrex G 2,5 with accurate of 0,040 m³/h; maximum pressure of 40 kPa, additionally was employed a gel of silica to remove the wet of gas. The load of bioreactor was made during four days, each day was used the same quantity until to complete the total load.

#### **Phase 5.** Principal variables to register

The relativity humidity and environment temperature were registered daily, was used a thermohygrometer with rank in temperature until 120°C and 100% in relativity humidity (Figure 4). The pH into the bioreactor was registered daily too, in this case was employed a digital pH-meter Hanna Instruments, with accurate of ± 0,2 (reference temperature of 20°C).

**Figure 3.** Installation of bioreactor and equipment to trituration

triturated and mixed with water in a relation of 1:2,5. In each test were taken samples of wastes and sludge to determinate the organic load, in addition was recorded daily the pH and the gas production. When the pretreatment of acidification ended, agricultural lime was added like at the first stage. The methodology employed to obtain the quantity of gas generated was the same of the first stage, was used a gas flow meter Metrex G2,5 with accurate of 0,040 m³/h and maximum pressure of 40 kPa. Samples of gas were collected in Tedlar bags and then were

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The organics load of wastes was obtained at the beginning and end of bioprocess; this included the total suspended solids (TSS), total solids (TS), volatile fatty acids (VFAs), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). The analytic method employed was the Standard Method by water and residual water like the first stage. Was calculated the production of gas (liters/day), hydrogen percentage (% de H2) and yield of biohydrogen (liters

**First and second phase:** The quantity and percentage of wastes generated at the Central Wholesaler of Antioquia during the year 2011 are show at the Table 3 and Figure 6. The highest production of wastes was associated to cabbage and lettuce leaves then wastes of citrics (orange and lemon) and finally wastes of mango, guava and others tropical fruits. The Figure 7 shows some pictures of wastes in the storage containers at the Central Wholesaler of Antioquia. With the information of production were selected wastes of cabbage and lettuce leaves, orange,

**Third phase:** The elemental analysis of wastes selected is show at the Table 4. To orange wastes, the relation C/N obtained was less than values reported in others research. In the others cases the results were close to values reported for wastes with similar characteristics. A relation

C/N close to 30 is considered appropriate to growth of anaerobic bacteria [22].

mango, papaya and guava to be employed at the bioprocess.

analyzed in a chromatographic gas (Perkin Elmer) to determinate its composition.

of H2/day).

**Figure 5.** Gas flow meter and Tedlar bag

**3.3. Results**

*3.3.1. First stage*

**Figure 4.** Thermohygrometer and pH-meter

The organics load was determined at the beginning and end of bioprocess; in this case the total suspended solids (TSS), total solids (TS), volatile fatty acids (VFAs), chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were determined. The analytics method employed were Standard Method by water and residual water of the APHA-AWWA-WPCF, edition 19 of 1995.

The production of gas was registered daily, samples were collected in Tedlar bags (with capacity of 1 liter, Figure 5) and then were analyzed in a chromatographic gas (Perkin Elmer) to establish its composition (percentage of CO2, O2, H2, CH4 and N2). During the tests, the wastes were subjected to an acid pretreatment to eliminate the methanogenic bacteria, after several days, agricultural lime was added to increase the pH until to obtain a value most adequate to the acidogenic bacteria.

#### *3.2.2. Second stage*

With the information from the first stage was elaborated an experiment with three treatments and three repetitions, were used three bioreactors of 2000 liters each them. The treatments were integrated by three values of duration to acid pretreatment (3, 7 and 10 days) and three values of pH to operation of the bioprocess (4,5 – 5,0; 5,1 – 5,5 and 5,6 – 6,0). The materials used were wastes of different fruits and vegetal from Central Wholesaler of Antioquia. The wastes were

**Figure 5.** Gas flow meter and Tedlar bag

triturated and mixed with water in a relation of 1:2,5. In each test were taken samples of wastes and sludge to determinate the organic load, in addition was recorded daily the pH and the gas production. When the pretreatment of acidification ended, agricultural lime was added like at the first stage. The methodology employed to obtain the quantity of gas generated was the same of the first stage, was used a gas flow meter Metrex G2,5 with accurate of 0,040 m³/h and maximum pressure of 40 kPa. Samples of gas were collected in Tedlar bags and then were analyzed in a chromatographic gas (Perkin Elmer) to determinate its composition.

The organics load of wastes was obtained at the beginning and end of bioprocess; this included the total suspended solids (TSS), total solids (TS), volatile fatty acids (VFAs), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). The analytic method employed was the Standard Method by water and residual water like the first stage. Was calculated the production of gas (liters/day), hydrogen percentage (% de H2) and yield of biohydrogen (liters of H2/day).

#### **3.3. Results**

#### *3.3.1. First stage*

**First and second phase:** The quantity and percentage of wastes generated at the Central Wholesaler of Antioquia during the year 2011 are show at the Table 3 and Figure 6. The highest production of wastes was associated to cabbage and lettuce leaves then wastes of citrics (orange and lemon) and finally wastes of mango, guava and others tropical fruits. The Figure 7 shows some pictures of wastes in the storage containers at the Central Wholesaler of Antioquia. With the information of production were selected wastes of cabbage and lettuce leaves, orange, mango, papaya and guava to be employed at the bioprocess.

**Third phase:** The elemental analysis of wastes selected is show at the Table 4. To orange wastes, the relation C/N obtained was less than values reported in others research. In the others cases the results were close to values reported for wastes with similar characteristics. A relation C/N close to 30 is considered appropriate to growth of anaerobic bacteria [22].


The chemical composition analysis of wastes showed that the highest values of volatile solids were found in the tropical fruits (mango, orange, guava and papaya). The volatile solids are the proportion of the raw material that bacteria using to generate biogas and have an out‐

Mango 97,4 15,1 14,71 Orange 96,6 14,3 13,81 Guava 96,7 15,3 14,79 Papaya 97,1 12,7 12,33 Lettuce and cabbage leaves 86,5 8 6,92

**Table 5.** Chemical composition analysis, (Chemical composition analysis laboratory, National University of Colombia)

In order to determinate the quantity of wastes to be used was obtained the density of each wastes, to this were taken samples and then were triturated, weighed and finally was calcu‐ lated the volume to employ. The bioreactor was loaded with 422 kilograms of wastes and 1110

kilograms of water, this provided an average relation (wastes: water) of 1:2,5.

**Waste ST (%) SV (%ST) SV (%)**

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standing role during the anaerobic fermentation process.

**Figure 7.** Pictures of wastes in the storage containers at the Central Wholesaler of Antioquia

**Figure 6.** Percentage of wastes generated at the Central Wholesaler of Antioquia, year 2011


**Table 4.** Result of elemental analysis on dry basis (%), (Coil laboratory, National University of Colombia)

**Figure 7.** Pictures of wastes in the storage containers at the Central Wholesaler of Antioquia

The chemical composition analysis of wastes showed that the highest values of volatile solids were found in the tropical fruits (mango, orange, guava and papaya). The volatile solids are the proportion of the raw material that bacteria using to generate biogas and have an out‐ standing role during the anaerobic fermentation process.


**Table 5.** Chemical composition analysis, (Chemical composition analysis laboratory, National University of Colombia)

In order to determinate the quantity of wastes to be used was obtained the density of each wastes, to this were taken samples and then were triturated, weighed and finally was calcu‐ lated the volume to employ. The bioreactor was loaded with 422 kilograms of wastes and 1110 kilograms of water, this provided an average relation (wastes: water) of 1:2,5.


oxygen demand was reduced in 63,6%. The environment temperature was between 21,8 y 31 °C, this mean that the biohydrogen production was developed under mesophilic conditions.

addition of lime

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

addition of lime

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week

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

week

**Analysis Beginning End**

SST (mg/l) 1920 325

The organics load showed an important reduction during the process, the total suspend solids were reduced in 83%, the chemical oxygen demand was reduced in 65% and the biochemical oxygen demand was reduced in 63,6%. The environment temperature was between 21,8 y 31 °C, this mean that the biohydrogen production was developed under mesophilic conditions. The average

The organics load showed an important reduction during the process, the total suspend solids were reduced in 83%, the chemical oxygen demand was reduced in 65% and the biochemical oxygen demand was reduced in 63,6%. The environment temperature was between 21,8 y 31 °C, this mean that the biohydrogen production was developed under mesophilic conditions. The average

> **Analysis Beginning End**  SST (mg/l) 1920 325 STV(mg/l) 54815 8296 ST(mg/l) 62395 9893 COD(mg/lO2) 54000 19133 BOD(mg/lO2) 37633 13713

**Analysis Beginning End**  SST (mg/l) 1920 325 STV(mg/l) 54815 8296 ST(mg/l) 62395 9893 COD(mg/lO2) 54000 19133 BOD(mg/lO2) 37633 13713

The gas production started three days after application of agricultural lime and continued for 22 days more. The hydrogen (biohydrogen) percentage found in gas ranged between 6,37 y 17,26; with a percentage of hydrogen less than 13,3; there was carbon dioxide and nitrogen in the biogas, however when the percentage of hydrogen was greater than 13,3; the gas composition was only hydrogen and carbon dioxide. The greater value of methane was 1,25% and less was 0%, this mean that the pretreatment to reduce

The gas production started three days after application of agricultural lime and continued for 22 days more. The hydrogen (biohydrogen) percentage found in gas ranged between 6,37 y 17,26; with a percentage of hydrogen less than 13,3; there was carbon dioxide and nitrogen in the biogas, however when the percentage of hydrogen was greater than 13,3; the gas composition was only hydrogen and carbon dioxide. The greater value of methane was 1,25% and less was 0%, this mean that the pretreatment to reduce

**Relative**

**humidity (%)**

**Relative**

**humidity (%)**

STV(mg/l) 54815 8296

ST(mg/l) 62395 9893

Table 7. Organic load of wastes at the first stage (Laboratory of Sanitary Engineering, National University of Colombia)

COD(mg/lO2) 54000 19133

BOD(mg/lO2) 37633 13713

**Table 7.** Organic load of wastes at the first stage (Laboratory of Sanitary Engineering, National University of Colombia)

Table 7. Organic load of wastes at the first stage (Laboratory of Sanitary Engineering, National University of Colombia)

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96

**day**

Temperatura Humedad relativa

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96

**day**

Temperatura Humedad relativa

The average relative humidity was between 38 y 73%.

relative humidity was between 38 y 73%.

Figure 9. Behavior of pH during the first stage

Figure 10.Behavior of temperature and relative humidity average

Figure 10.Behavior of temperature and relative humidity average

**Figure 10.** Behavior of temperature and relative humidity average

the methanogenic bacteria was satisfactory.

the methanogenic bacteria was satisfactory.

Figure 9. Behavior of pH during the first stage

relative humidity was between 38 y 73%.

**Fifth phase:** 

**Temperature (°C)**

**Temperature (°C)**

3 3.5 4 4.5 5 5.5 6 6.5

**Fifth phase:** 

**Figure 9.** Behavior of pH during the first stage

3 3.5 4 4.5 5 5.5 6 6.5

pH

pH

**Table 6.** Quantity of wastes and water to the fermentation process

#### **Fourth phase:**

Each waste was triturated and mixed with water during three minutes until to reach an average size of 2 centimeters. In order to reduce the quantity of methanogenic bacteria, the wastes were submitted to acidic conditions during three months with a value of pH close to 3,5. Afterwards was added during three days agricultural lime until to reach a pH of 6,2; in that moment the production of biohydrogen started. The quantity of agricultural lime added was 7 kilograms (Figure 9).

**Figure 8.** Bioreactor used by the first stage and wastes triturated

#### **Fifth phase:**

The organics load showed an important reduction during the process, the total suspend solids were reduced in 83%, the chemical oxygen demand was reduced in 65% and the biochemical

5 5.5 Figure 9. Behavior of pH during the first stage **Figure 9.** Behavior of pH during the first stage

4.5

**Fifth phase:** 

20

pH

6

oxygen demand was reduced in 63,6%. The environment temperature was between 21,8 y 31 °C, this mean that the biohydrogen production was developed under mesophilic conditions. The average relative humidity was between 38 y 73%. 3 3.5 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 week lime The organics load showed an important reduction during the process, the total suspend solids were reduced in 83%, the chemical oxygen demand was reduced in 65% and the biochemical oxygen demand was reduced in 63,6%. The environment temperature was between 21,8 y 31 °C, this mean that the biohydrogen production was developed under mesophilic conditions. The average relative humidity was between 38 y 73%.

addition of


**Table 7.** Organic load of wastes at the first stage (Laboratory of Sanitary Engineering, National University of Colombia) BOD(mg/lO2) 37633 13713 Table 7. Organic load of wastes at the first stage (Laboratory of Sanitary Engineering, National University of Colombia) 30 30 **Relative Temperature**

The gas production started three days after application of agricultural lime and continued for 22 days more. The hydrogen (biohydrogen) percentage found in gas ranged between 6,37 y 17,26; with a percentage of hydrogen less than 13,3; there was carbon dioxide and nitrogen in the biogas, however when the percentage of hydrogen was greater than 13,3; the gas composition was only hydrogen and carbon dioxide. The greater value of methane was 1,25% and less was 0%, this mean that the pretreatment to reduce

20

Figure 10.Behavior of temperature and relative humidity average **Figure 10.** Behavior of temperature and relative humidity average

the methanogenic bacteria was satisfactory.

The gas production started three days after application of agricultural lime and continued for 22 days more. The hydrogen (biohydrogen) percentage found in gas ranged between 6,37 y 17,26; with a percentage of hydrogen less than 13,3; there was carbon dioxide and nitrogen in the biogas, however when the percentage of hydrogen was greater than 13,3; the gas compo‐ sition was only hydrogen and carbon dioxide. The greater value of methane was 1,25% and less was 0%, this mean that the pretreatment to reduce the methanogenic bacteria was satisfactory.


**Figure 12.** Production daily of hydrogen

Figure 13.Production accumulated of hydrogen

**Installation of bioreactors and wastes to use** 

Figure 14.Set of bioreactors employed at the second stage

1

Table 9. Wastes used in each repetition

At the second stage were used the same wastes of first stage, but additionally were employed wastes of tomato, onion, garlic and husk of cape gooseberry (Table 10). The wastes were triturated and mixed with water during three minutes, the relation of wastes: water was 1:2,5 like at first stage. The quantity of wastes employed in each treatment was similar to quantity used at first stage. The

**Repetition Wastes Quantity of wastes (kg)** 

Average 485,3 488 434,3

The highest values of chemical oxygen demand (COD) were obtained in the treatment 2 during the repetition 1 and the treatments 1 and 3 of the repetition 3 respectively, namely in these cases there were more quantity of food available to the microorganisms.

and husk of cape gooseberry 450 450 450

and papaya 500 500 400

Lettuce and cabbage leaves, tomato, onion, garlic, pimento, orange, lemon, mango, guava and papaya

<sup>2</sup>Lettuce and cabbage leaves, tomato, onion, garlic

<sup>3</sup>Lettuce and cabbage leaves, orange, mango, guava

T1 T2 T3

506 514 453

volume of work in each bioreactor was 70% and 30% was dedicated to storage the gas generated.

At the second stage were used the same wastes of first stage, but additionally were employed wastes of tomato, onion, garlic and husk of cape gooseberry (Table 10). The wastes were triturated and mixed with water during three minutes, the relation of wastes: water was 1:2,5 like at first stage. The quantity of wastes employed in each treatment was similar to quantity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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**day**

**3.3.2. Second stage** 

**Installation of bioreactors and wastes to use**

**Figure 13.** Production accumulated of hydrogen

*3.3.2. Second stage*

**production**

**accumulated of H2 (liters)**

ND: not detected

**Table 8.** Composition of gas generated (Coil laboratory, National University of Colombia)

The total production of hydrogen was 177 liters in 22 days, with a maximum value of 14,5 liters, an average of 7,4 liters of H2/day and maximum yield of 83 liters of H2/m3 of bioreactor. The maximum value of generation of hydrogen was registered 7 days after from started the gas production and the maximum rate of hydrogen generation was obtained between first and seventh days. The Figure 12 shows a several pictures of biohydrogen generated, the color blue is from silica gel used to remove the wet of the gas. The quantity of organic load removed was 26.400 mg/liter of O2, (COD).

Source: Information personal from research

**Figure 11.** Pictures of biohydrogen generated

**Figure 12.** Production daily of hydrogen

Figure 13.Production accumulated of hydrogen **Figure 13.** Production accumulated of hydrogen

#### **3.3.2. Second stage**  *3.3.2. Second stage*

#### **Installation of bioreactors and wastes to use Installation of bioreactors and wastes to use**

Figure 14.Set of bioreactors employed at the second stage

1

Table 9. Wastes used in each repetition

At the second stage were used the same wastes of first stage, but additionally were employed wastes of tomato, onion, garlic and husk of cape gooseberry (Table 10). The wastes were triturated and mixed with water during three minutes, the relation of wastes: water was 1:2,5 like at first stage. The quantity of wastes employed in each treatment was similar to quantity used at first stage. The volume of work in each bioreactor was 70% and 30% was dedicated to storage the gas generated. At the second stage were used the same wastes of first stage, but additionally were employed wastes of tomato, onion, garlic and husk of cape gooseberry (Table 10). The wastes were triturated and mixed with water during three minutes, the relation of wastes: water was 1:2,5 like at first stage. The quantity of wastes employed in each treatment was similar to quantity

**Repetition Wastes Quantity of wastes (kg)** 

Average 485,3 488 434,3

The highest values of chemical oxygen demand (COD) were obtained in the treatment 2 during the repetition 1 and the treatments 1 and 3 of the repetition 3 respectively, namely in these cases there were more quantity of food available to the microorganisms.

and husk of cape gooseberry 450 450 450

and papaya 500 500 400

Lettuce and cabbage leaves, tomato, onion, garlic, pimento, orange, lemon, mango, guava and papaya

<sup>2</sup>Lettuce and cabbage leaves, tomato, onion, garlic

<sup>3</sup>Lettuce and cabbage leaves, orange, mango, guava

T1 T2 T3

506 514 453

used at first stage. The volume of work in each bioreactor was 70% and 30% was dedicated to storage the gas generated.

**Behavior of pH during the pretreatment and operation of bioreactors**

quate to generate biohydrogen.

**Figure 15.** Behavior of pH in each treatment and repetition

**Production of biohydrogen**

Due to type of wastes employed in the repetition 2, was necessary to add muriatic acid into all bioreactors to achieve the pH of acidification, but there were not response (pH be‐ tween 3,5 and 4,5). However, during the repetitions 1 and 3, in all treatments was used wastes of orange and lemon, this allowed to apply the pretreatment of acidification, after‐ wards was added agricultural lime and was reached a pH between 5 and 6, values ade‐

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The gas generated in all treatments was compound of hydrogen, carbon dioxide, nitrogen and oxygen. The greater value of methane was 3,7% and the less was 0%, in many times the methane was not detected (ND), this mean that the pretreatment to reduce the methanogenic bacteria was satisfactory. The percentage of hydrogen in gas was between 5 and 18,08; this was the highest value in the research and was obtained in the treatment 3 during the repetition 3 when the wastes used were Lettuce and cabbage leaves, orange, lemon and papaya. In the repetition 2 in all treatments, there were not generation of hydrogen (NG). The oxygen content in some repetitions show maybe that some air entered to bioreactor when the samples were taken.

**Figure 14.** Set of bioreactors employed at the second stage


**Table 9.** Wastes used in each repetition

The highest values of chemical oxygen demand (COD) were obtained in the treatment 2 during the repetition 1 and the treatments 1 and 3 of the repetition 3 respectively, namely in these cases there were more quantity of food available to the microorganisms.


**Table 10.** Organic composition of wastes employed

#### **Behavior of pH during the pretreatment and operation of bioreactors**

Due to type of wastes employed in the repetition 2, was necessary to add muriatic acid into all bioreactors to achieve the pH of acidification, but there were not response (pH be‐ tween 3,5 and 4,5). However, during the repetitions 1 and 3, in all treatments was used wastes of orange and lemon, this allowed to apply the pretreatment of acidification, after‐ wards was added agricultural lime and was reached a pH between 5 and 6, values ade‐ quate to generate biohydrogen.

**Figure 15.** Behavior of pH in each treatment and repetition

#### **Production of biohydrogen**

The gas generated in all treatments was compound of hydrogen, carbon dioxide, nitrogen and oxygen. The greater value of methane was 3,7% and the less was 0%, in many times the methane was not detected (ND), this mean that the pretreatment to reduce the methanogenic bacteria was satisfactory. The percentage of hydrogen in gas was between 5 and 18,08; this was the highest value in the research and was obtained in the treatment 3 during the repetition 3 when the wastes used were Lettuce and cabbage leaves, orange, lemon and papaya. In the repetition 2 in all treatments, there were not generation of hydrogen (NG). The oxygen content in some repetitions show maybe that some air entered to bioreactor when the samples were taken.


The maximum production of biohydrogen per day obtained at the first stage was 15 liters, however at the second stage the maximum production was 38 liters, this mean that the production was duplicated during the second stage. In the repetition 3, in the treatment 3 were generated 32 liters of biohydrogen, meanwhile in the treatment 1 were generated 15 liters. The wastes employed in both treatments were Lettuce and cabbage leaves, orange, lemon and tropical fruits as mango, guava and papaya, the initial pH was lesser to 4,5 during 7 and 8

initial pH was lesser to 4,5 during 7 and 8 days, and the pH of bioreactors operation was between 5 and 5,5.

1 3 5 7 9 11 13 15 17 19 21 23 25

The greater accumulated production was reached in the treatment 2 and the repetition 1, followed by the treatment 3 in the repetition 3. In both cases were used vegetal wastes and tropical fruits in same proportions in addition, initially the wastes were subjected to acid conditions with a pH less to 4,0 during 8 days and a pH for operation of bioreactor between 5 and 5,5. Under those conditions the hydrogen content into gas ranged between 7,5 and 10,5%. The total production of hydrogen in the treatment 2 and the repetition 1 was 317,8 liters in 22 days, with 14,44 liters of H2/day (twice the result from the first stage), and maximum yield of 159 liters of H2/m3 of bioreactor. Other outstanding result was reached when were employed the same wastes, at beginning were applied acid conditions during 7 days under a pH less to 4,5; and then was used a pH for the operation of bioreactor between 5 and 5,5. In this case the percentage of hydrogen into gas ranged between 5 and 18,08% (the last value was the maxi‐ mum content reached in the research). The production of hydrogen was 231,1 liters of H2 in 22 days with 10,5 liters of H2/day (duplicated the value reached from the first stage) and a

of bioreactor.

Ensayo 3. T 1 Ensayo 3. T 2 Ensayo 3. T 3

**day** Ensayo 1. T 1 Ensayo 1. T 2 Ensayo 1. T 3 Ensayo 2. T 3

3 4,0 0,02 77,3 18,1 ND

1 NG NG NG NG NG 2 NG NG NG NG NG 3 NG NG NG NG NG

1 11,4 5,5 41 13,4 0,2 2 37,8 5,5 36,2 5,4 0,5 3 20,1 5,7 43,5 12 3,3

1 NG NG NG NG NG 2 NG NG NG NG NG 3 NG NG NG NG NG

1 29,08 7,5 50,3 3,0 0,2 2 23,88 6,5 41,7 10,3 2,6 3 42,14 8,2 36,1 7,1 1,4

1 28 7,0 52,2 4,4 0,1 2 45,29 5,8 38,1 3,0 0,1 3 40,69 5,3 40,8 3,2 0,1

1 8,96 18,0 51,3 12,1 0,2 2 43,32 6,3 36,5 7,1 0,7 3 52,85 5,0 30,5 5,1 0,3

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**Treatment Sample CO2 (%) H2 (%) N2 (%) O2 (%) CH4 (%)** 

**Treatment Sample CO2 (%) H2 (%) N2 (%) O2 (%) CH4 (%)** 

Generation of Biohydrogen by Anaerobic Fermentation of Organics Wastes in Colombia

The maximum production of biohydrogen per day obtained at the first stage was 15 liters, however at the second stage the maximum production was 38 liters, this mean that the production was duplicated during the second stage. In the repetition 3, in the treatment 3 were generated 32 liters of biohydrogen, meanwhile in the treatment 1 were generated 15 liters. The wastes employed in both treatments were Lettuce and cabbage leaves, orange, lemon and tropical fruits as mango, guava and papaya, the

days, and the pH of bioreactors operation was between 5 and 5,5.

Table 11. Composition of gas generated, first repetition

1

2

3

1

2

3

Table 13. Composition of gas generated, third repetition

ND: not detected NG: not generated

Figure 16.Production of hydrogen

maximum yield of 115,6 liters of H2/m3

**Production of H2 (liters /day)**

**Figure 16.** Production of hydrogen

Table 12. Composition of gas generated, second repetition

**Table 11.** Composition of gas generated, first repetition


**Table 12.** Composition of gas generated, second repetition


ND: not detected

NG: not generated

**Table 13.** Composition of gas generated, third repetition

the treatment 3 were generated 32 liters of biohydrogen, meanwhile in the treatment 1 were generated 15 liters. The wastes employed in both treatments were Lettuce and cabbage leaves, orange, lemon and tropical fruits as mango, guava and papaya, the

**Treatment Sample CO2 (%) H2 (%) N2 (%) O2 (%) CH4 (%)** 

3 4,0 0,02 77,3 18,1 ND

1 NG NG NG NG NG 2 NG NG NG NG NG 3 NG NG NG NG NG

1 11,4 5,5 41 13,4 0,2 2 37,8 5,5 36,2 5,4 0,5 3 20,1 5,7 43,5 12 3,3

1 NG NG NG NG NG 2 NG NG NG NG NG 3 NG NG NG NG NG

1 29,08 7,5 50,3 3,0 0,2 2 23,88 6,5 41,7 10,3 2,6 3 42,14 8,2 36,1 7,1 1,4

1 28 7,0 52,2 4,4 0,1

1 8,96 18,0 51,3 12,1 0,2

**Treatment Sample CO2 (%) H2 (%) N2 (%) O2 (%) CH4 (%)** 

The maximum production of biohydrogen per day obtained at the first stage was 15 liters, however at the second stage the maximum production was 38 liters, this mean that the production was duplicated during the second stage. In the repetition 3, in the treatment 3 were generated 32 liters of biohydrogen, meanwhile in the treatment 1 were generated 15 liters. The wastes employed in both treatments were Lettuce and cabbage leaves, orange, lemon and tropical fruits as mango, guava and papaya, the initial pH was lesser to 4,5 during 7 and 8 days, and the pH of bioreactors operation was between 5 and 5,5. 3 2 43,32 6,3 36,5 7,1 0,7 3 52,85 5,0 30,5 5,1 0,3 Table 13. Composition of gas generated, third repetition ND: not detected NG: not generated The maximum production of biohydrogen per day obtained at the first stage was 15 liters, however at the second stage the maximum production was 38 liters, this mean that the production was duplicated during the second stage. In the repetition 3, in

initial pH was lesser to 4,5 during 7 and 8 days, and the pH of bioreactors operation was between 5 and 5,5.

Table 11. Composition of gas generated, first repetition

1

2

3

1

Table 12. Composition of gas generated, second repetition

**Figure 16.** Production of hydrogen

Figure 16.Production of hydrogen

The greater accumulated production was reached in the treatment 2 and the repetition 1, followed by the treatment 3 in the repetition 3. In both cases were used vegetal wastes and tropical fruits in same proportions in addition, initially the wastes were subjected to acid conditions with a pH less to 4,0 during 8 days and a pH for operation of bioreactor between 5 and 5,5. Under those conditions the hydrogen content into gas ranged between 7,5 and 10,5%. The total production of hydrogen in the treatment 2 and the repetition 1 was 317,8 liters in 22 days, with 14,44 liters of H2/day (twice the result from the first stage), and maximum yield of 159 liters of H2/m3 of bioreactor. Other outstanding result was reached when were employed the same wastes, at beginning were applied acid conditions during 7 days under a pH less to 4,5; and then was used a pH for the operation of bioreactor between 5 and 5,5. In this case the percentage of hydrogen into gas ranged between 5 and 18,08% (the last value was the maxi‐ mum content reached in the research). The production of hydrogen was 231,1 liters of H2 in 22 days with 10,5 liters of H2/day (duplicated the value reached from the first stage) and a maximum yield of 115,6 liters of H2/m3 of bioreactor.

value reached from the first stage) and a maximum yield of 115,6 liters of H2/m3 of bioreactor.

The greater accumulated production was reached in the treatment 2 and the repetition 1, followed by the treatment 3 in the repetition 3. In both cases were used vegetal wastes and tropical fruits in same proportions in addition, initially the wastes were subjected to acid conditions with a pH less to 4,0 during 8 days and a pH for operation of bioreactor between 5 and 5,5. Under those conditions the hydrogen content into gas ranged between 7,5 and 10,5%. The total production of hydrogen in the treatment 2 and the repetition 1 was 317,8 liters in 22 days, with 14,44 liters of H2/day (twice the result from the first stage), and maximum yield of 159 liters of H2/m3 of bioreactor. Other outstanding result was reached when were employed the same wastes, at beginning were

reached in the research). The production of hydrogen was 231,1 liters of H2 in 22 days with 10,5 liters of H2/day (duplicated the

The results shows that is feasible to produce biohydrogen (hydrogen) when are employed organic wastes from the Central Wholesaler of Antioquia. The wastes should be submitted to a pretreatment acid with a pH between 3,5 y 4,0; during 7 days (or less), then the operation pH should be increased until a value between 5 and 5,5. The chemical oxygen demand (COD) should be between 20.000 and 54.000 mg/liter of O2, this is possible to reach when in the bioprocess is employed a proportion similar of tropical fruit waste and vegetal waste.

Generation of Biohydrogen by Anaerobic Fermentation of Organics Wastes in Colombia

**•** It was possible to generate hydrogen from organic wastes of Central Wholesaler of Antio‐

**•** The chemical oxygen demand (COD) promoted the biohydrogen production, the best results were obtained to values between 20.000 and 54.000 mg/liter of O2. These values were

**•** There was not generation of biohydrogen when the bioprocess started with a pH upper than 4. This ratifies that to generate biohydrogen by anaerobic fermentation is necessary to apply a pretreatment, in this research, a pretreatment under acid conditions (pH between 3,5 and

**•** Colombiahasahighpotentialtogeneratehydrogenbyanaerobic fermentationdue toorganic

**•** The results show that is possible to produce biohydrogen by anaerobic fermentation of

The authors acknowledge to National University of Colombia in Medellín and the Central

, Deisy Juliana Cano Quintero and

Engineering Agricultural Department, National University of Colombia, Medellín,

an energetic potential of 144 GW, value upper than the installed potential (13,5 GW).

of biohydrogen and supply

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achieved with a heterogeneous mix of fruits and vegetal wastes.

wastes available, these wastes could generate until 28'825.609 m3

organic wastes and providing new sources energetic.

Wholesaler of Antioquia by the financial support to research.

\*Address all correspondence to: elmorenoc@unal.edu.co

**5. Conclusions**

4,0) was successful.

**Acknowledgements**

**Author details**

Colombia

Edilson León Moreno Cárdenas\*

Cortés Marín Elkin Alonso

quia and to improve the bioprocess.

repetition 3, the maximum value was obtained with the treatment 2 in the repetition 1 in which were used wastes from lettuce and

Figure 17.Production accumulated of hydrogen **Figure 17.** Production accumulated of hydrogen

**4. Final analysis** 

#### Two treatments showed the highest production of biohydrogen, the treatment 2 in the repetition 1 and the treatment 3 in the **4. Final analysis**

cabbage leaves, tomato, onion, garlic, pimento, orange, lemon, mango, guava and papaya. The acid conditions were implemented 8 days with value of pH near to 4, the operation of bioreactor was between 5 and 5,5. In the treatment 3 in the repetition 3 were used the same wastes, the acid condition was applied during 7 days with value of pH near to 4,5; the pH of bioreactor operation was between 5 and 5,5. Although was generated more quantity of hydrogen in the treatment 2 during the repetition 1, was in the treatment 3 in the repetition 3 where was obtained the greater hydrogen content in the gas (18,04%) and greater rate of generation of hydrogen. The maximum production of hydrogen was obtained at the second stage when the pretreatment of acidification was applied during 8 days with a value for the pH of 4, a pH of reactor operation between 5 and 5,5; and a value of chemical oxygen demand (COD) near to 20.000 mg/liter of O2. At the first stage when was used a quantity of wastes from tropical fruits greater than wastes of lettuce and cabbage leaves, the chemical oxygen demand (COD) initial was 54.000 mg/liter of O2, however the hydrogen production was significantly less respect to second stage. This indicates that a high value of chemical oxygen demand could inhibit the hydrogen generation; this result is according to reports of different authors [13, 23-29]. When were used vegetal wastes (without wastes of tropical fruits) as lettuce and cabbage leaves, tomato, onion, garlic and husk of cape gooseberry, there were no Two treatments showed the highest production of biohydrogen, the treatment 2 in the repetition 1 and the treatment 3 in the repetition 3, the maximum value was obtained with the treatment 2 in the repetition 1 in which were used wastes from lettuce and cabbage leaves, tomato, onion, garlic, pimento, orange, lemon, mango, guava and papaya. The acid conditions were implemented 8 days with value of pH near to 4, the operation of bioreactor was between 5 and 5,5. In the treatment 3 in the repetition 3 were used the same wastes, the acid condition was applied during 7 days with value of pH near to 4,5; the pH of bioreactor operation was between 5 and 5,5. Although was generated more quantity of hydrogen in the treatment 2 during the repetition 1, was in the treatment 3 in the repetition 3 where was obtained the greater hydrogen content in the gas (18,04%) and greater rate of generation of hydrogen.

acid conditions at beginning the process and was necessary to add acid, however there was no response in the biosystems and the pH always was upper than 4,5. Under these conditions there was no production of hydrogen. In addition the chemical oxygen demand was low (12.000 mg/liter of O2). The results shows that is feasible to produce biohydrogen (hydrogen) when are employed organic wastes from the Central Wholesaler of Antioquia. The wastes should be submitted to a pretreatment acid with a pH between 3,5 y 4,0; during 7 days (or less), then the operation pH should be increased until a value between 5 and 5,5. The chemical oxygen demand (COD) should be between 20.000 and 54.000 mg/liter of O2, this is possible to reach when in the bioprocess is employed a proportion similar of tropical fruit waste and vegetal waste. **5. Conclusions**  The maximum production of hydrogen was obtained at the second stage when the pretreat‐ ment of acidification was applied during 8 days with a value for the pH of 4, a pH of reactor operation between 5 and 5,5; and a value of chemical oxygen demand (COD) near to 20.000 mg/liter of O2. At the first stage when was used a quantity of wastes from tropical fruits greater than wastes of lettuce and cabbage leaves, the chemical oxygen demand (COD) initial was 54.000 mg/liter of O2, however the hydrogen production was significantly less respect to second stage. This indicates that a high value of chemical oxygen demand could inhibit the hydrogen generation; this result is according to reports of different authors [13, 23-29]. When were used vegetal wastes (without wastes of tropical fruits) as lettuce and cabbage leaves, tomato, onion, garlic and husk of cape gooseberry, there were no acid conditions at beginning the process and was necessary to add acid, however there was no response in the biosystems and the pH always was upper than 4,5. Under these conditions there was no production of hydrogen. In addition the chemical oxygen demand was low (12.000 mg/liter of O2).

The results shows that is feasible to produce biohydrogen (hydrogen) when are employed organic wastes from the Central Wholesaler of Antioquia. The wastes should be submitted to a pretreatment acid with a pH between 3,5 y 4,0; during 7 days (or less), then the operation pH should be increased until a value between 5 and 5,5. The chemical oxygen demand (COD) should be between 20.000 and 54.000 mg/liter of O2, this is possible to reach when in the bioprocess is employed a proportion similar of tropical fruit waste and vegetal waste.

#### **5. Conclusions**


### **Acknowledgements**

The authors acknowledge to National University of Colombia in Medellín and the Central Wholesaler of Antioquia by the financial support to research.

#### **Author details**

Edilson León Moreno Cárdenas\* , Deisy Juliana Cano Quintero and Cortés Marín Elkin Alonso

\*Address all correspondence to: elmorenoc@unal.edu.co

Engineering Agricultural Department, National University of Colombia, Medellín, Colombia

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[24] Chenlin L, Fang H. Fermentative hydrogen production from wasteswater and solid wastes by mixed cultures. Critical Reviews in Environmental Science and Technology

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[26] Das D, Veziroglu T.N. Hydrogen production by biological processes: a survey of

[27] Hawkes F.R, Hussy I, Kyazze G, Dinsdale R, Hawkes D.L. Continuous dark fermen‐ tative hydrogen production by mesophilic microflora: Principles and progress.

[28] Hwanga J.J, Chang W.R. Life-cycle analysis of greenhouse gas emission and energy efficiency of hydrogen fuel cell scooters. International Journal of Hydrogen Energy

literature. International Journal of Hydrogen Energy 2001; 26(16) 13-28.

national Journal of Hydrogen Energy 2011; 36(12) 7089-7093.

addition. Enzyme and Microbial Technology 2009; 45(3)181-187.

Medellín: Universidad Nacional de Colombia; 2000.

Vegetal Waste. Process Biochemistry 2004; 39 (12) 2143-2178.

national Journal of Hydrogen Energy 2008; 33(21) 6046-6057.

International Journal of Hydrogen Energy 2007; 32(2) 172-184.

rate. International Journal of Hydrogen Energy 2009; 34(10) 4296-4304.

2010; 35(21) 11746-11755.

Sede Medellín, 2010.

2004; 29(13) 1355-1363.

20011.

2007; 37(1) 1-39.

2010; 35(21) 11947-11956.


[29] Nishio N, Nakashimada Y. High rate production of hydrogen/methane from various substrates and wastes. Advances in Biochemical Engineering/Biotechnology 2004; 90 63-87.

**Chapter 13**

**Hydrogen Conversion in**

Vitalij Yukhymenko, Eugen Martysh,

Alexandr Tsimbaliuk, Leonid Simonchik,

Valentina Demchina and Semen Dragnev

http://dx.doi.org/10.5772/53764

**1. Introduction**

Additional information is available at the end of the chapter

**DC and Impulse Plasma-Liquid Systems**

Valeriy Chernyak, Oleg Nedybaliuk, Sergei Sidoruk,

Olena Solomenko, Yulia Veremij, Dmitry Levko,

Andrej Kirilov, Oleg Fedorovich, Anatolij Liptuga,

It is well known [1] that hydrogen (H2) as the environmentally friendly fuel is considered to be one of the future most promising energy sources. Recently, interest in hydrogen energy has increased significantly, mainly due to the energy consumption increase in the world, and recent advances in the fuel cell technology. According to the prognosis, in the next decades, global energy consumption will be increased by 59%, and still most of this energy will be extracted from the fossil fuels. Because of the traditional fossil fuels depletion, today there's a growing interest in renewable energy sources (f.e. – bioethanol, biodiesel). Bioethanol can be obtained from the renewable biomass, also it can be easily and safely transported due to its low toxicity, but it's not a very good fuel. Modern biodiesel production technologies are

characterized by a high percentage of waste (bioglycerol) which is hard to recycle.

It is common knowledge [2] that addition of the syn-gas to the fuel (H2 and CO) improves the combustion efficiency: less burning time, rapid propagation of the combustion wave, burning stabilization, more complete mixture combustion and reduction of dangerous emissions (NOx). Besides, the synthesis gas is an important stuff raw for the various materials and synthetic fuels synthesizing. There are many methods of synthesis gas (including hydrogen) production, for example – steam reforming and partial liquid hydrocarbons oxidation. Also,

> © 2013 Chernyak et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Chernyak et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **Chapter 13**

### **Hydrogen Conversion in DC and Impulse Plasma-Liquid Systems**

Valeriy Chernyak, Oleg Nedybaliuk, Sergei Sidoruk, Vitalij Yukhymenko, Eugen Martysh, Olena Solomenko, Yulia Veremij, Dmitry Levko, Alexandr Tsimbaliuk, Leonid Simonchik, Andrej Kirilov, Oleg Fedorovich, Anatolij Liptuga, Valentina Demchina and Semen Dragnev

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53764

**1. Introduction**

It is well known [1] that hydrogen (H2) as the environmentally friendly fuel is considered to be one of the future most promising energy sources. Recently, interest in hydrogen energy has increased significantly, mainly due to the energy consumption increase in the world, and recent advances in the fuel cell technology. According to the prognosis, in the next decades, global energy consumption will be increased by 59%, and still most of this energy will be extracted from the fossil fuels. Because of the traditional fossil fuels depletion, today there's a growing interest in renewable energy sources (f.e. – bioethanol, biodiesel). Bioethanol can be obtained from the renewable biomass, also it can be easily and safely transported due to its low toxicity, but it's not a very good fuel. Modern biodiesel production technologies are characterized by a high percentage of waste (bioglycerol) which is hard to recycle.

It is common knowledge [2] that addition of the syn-gas to the fuel (H2 and CO) improves the combustion efficiency: less burning time, rapid propagation of the combustion wave, burning stabilization, more complete mixture combustion and reduction of dangerous emissions (NOx). Besides, the synthesis gas is an important stuff raw for the various materials and synthetic fuels synthesizing. There are many methods of synthesis gas (including hydrogen) production, for example – steam reforming and partial liquid hydrocarbons oxidation. Also,

© 2013 Chernyak et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Chernyak et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

there is an alternative approach – biomass reforming with low-temperature plasma assistance. Plasma is a very powerful source of active particles (electrons, ions, radicals, etc.), and therewith it can be catalyst for the various chemical processes activation. However, a major disadvantage of chemical processes plasma catalysis is weak processes control.

tion of chemical warfare agents. When mixed with other substances scH2O can be used not only for oxidation but also in the reactions of hydrolysis, hydration, the formation and

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Besides, the use of pulsed electrical discharges in the liquid brings up new related factors: strong ultraviolet emission and acoustic or shock waves. In literature it can be found that systems with energies more than 1 kJ/pulse, that have negative influence on the lifetime of such systems. Reasonable from this perspective is the usage of pulsed systems with relatively low pulse energy and focusing of acoustic waves. In addition, the acoustic oscillations in such systems can be used as an additional mechanism of influence on chemical transformations. In using of acoustic oscillations for chemical reactions the most attention is paid to systems with strong convergent waves. However, the processes during the collapse of the powerful convergent waves are studied unsufficiently. In the literature the systems of cylindrical, spherical or parabolic surfaces used in the focusing of shock waves for technological needs are known [8]. However, among their disadvantages should be noted that partial usage of the energy of acoustic wave and the problem of it's peripheral sources synchronization, which leads to distortion of the shock wave front ideality and reduces the focusing effectiveness.

Probably, more perspective method of using acoustic waves is their generation by single axial pulse electric discharge with further reflection from an ideal cylindrical surface. This approach can provide better symmetry of compression by convergent acoustic wave both in the gas and

In addition, the re-ignition of electrical discharge at the moment of collapse convergent acoustic waves can lead to the plasma temperature increasing due to compression of the discharge

It's clear that plasma-liquid systems (PLS) mentioned above have some sharp differences. Therefore, the first section of this article presents the results of our research on the addition of CO2 to the "TORNADO-LE". And the second section of the article is devoted to investigation

**2. Bioethanol and bioglycerol conversion in "tornado" type plasma-liquid**

The experimental setting is shown in Fig. 1. Its base is a cylindrical quartz chamber (1) with diameter of 90 mm and height of 50 mm. Top (2) and bottom (3) it is hermetically closed with metal flanges. Camera is filled with fluid (4), the level of which has been maintained by the injection pump through the hole (5). Bottom flange is made of stainless steel. The stainless steel T-shaped cylindrical electrode (6), cooled with water, immerses in the liquid through the central hole in the bottom flange. There is a 5 mm thick metal washer on its surface (7) in the middle of which there is a hole in diameter of 10 mm. Sharp corners are rounded. This washer

in the liquid. Probably, such mechanism can be exploited for scH2O production

of double-impulse system in underwater electric discharge.

**system with the addition of CO2**

**2.1. Experimental set up**

channel, as well as the appropriate amplification of acoustic waves after the collapse.

destruction of carbon-carbon bonds, hydrogenation, and others.

There is a bundle of electrical discharges that generate both equilibrium and non equilibrium plasma. For plasma conversion – arc, corona, spark, microwave, radio frequency, barrier and other discharges are used. One of the most effective discharges for the liquid hydrocarbons plasma treatment is the "tornado" type reverse vortical gas flow plasma-liquid system with a liquid electrode ("TORNADO-LE") [3]. The main advantages of plasma-liquid systems are – high chemical plasma activity and good plasma-chemical conversions selectivity. It may guarantee high performance and conversion efficiency at the relatively low power consump‐ tion. Moreover, those are systems of atmospheric pressure and above, and this increases their technological advantages.

Also, syn-gas ratio – hydrogen and carbon monoxide concentration ratio should be mentioned. As well, it should be taken into consideration that for efficient combustion (in terms of energy) of the synthesis gas it should contain more hydrogen, and in the case of the synthesis materials – they should contain more CO.

Relatively new possible solution to this problem – carbon dioxide recycling. Many modern energy projects have difficulties with the large amount of CO2 storing and disposing. And it is also known that the addition of CO2 to plasma during the hydrocarbons reforming may help to control plasma-chemical processes [4]. That is why the objective of the research is to study the influence of different amounts of CO2 in the working gas on the plasma-chemical processes during the hydrocarbons conversion.

This research deals with hydrocarbons (bioethanol, bioglycerol) reforming by means of the combined system, which includes plasma processing and pyrolysis chamber. As a plasma source the "tornado" type reverse vortical gas flow plasma-liquid system with liquid electrode has been used [5].

Qualitatively new challenge is connected with a selectivity of the plasma chemistry strength‐ ening by the transition of the chemical industry to "green chemistry". The last is a transition from the traditional concept of evaluating the effectiveness of the chemical yield to the concept that evaluates the cost-effectiveness as the exclusion of hazardous waste and non-toxic and/or hazardous substances [6].

A quantitative measure of the environmental acceptability of chemical technology is the ecology factor, which is defined as the ratio of the mass of waste (waste) to the mass of principal product. Waste is all that is not the principal product.

By the way, the most promising approaches in green chemistry is the implementation of processes in supercritical liquids (water, carbon dioxide) [7].

Water in supercritical condition unlimitedly mixes with oxygen, hydrogen and hydrocarbons, facilitating their interaction with each other - oxidation reactions are very fast in scH2O (supercritical water). One particularly interesting application of this water - efficient destruc‐ tion of chemical warfare agents. When mixed with other substances scH2O can be used not only for oxidation but also in the reactions of hydrolysis, hydration, the formation and destruction of carbon-carbon bonds, hydrogenation, and others.

Besides, the use of pulsed electrical discharges in the liquid brings up new related factors: strong ultraviolet emission and acoustic or shock waves. In literature it can be found that systems with energies more than 1 kJ/pulse, that have negative influence on the lifetime of such systems. Reasonable from this perspective is the usage of pulsed systems with relatively low pulse energy and focusing of acoustic waves. In addition, the acoustic oscillations in such systems can be used as an additional mechanism of influence on chemical transformations.

In using of acoustic oscillations for chemical reactions the most attention is paid to systems with strong convergent waves. However, the processes during the collapse of the powerful convergent waves are studied unsufficiently. In the literature the systems of cylindrical, spherical or parabolic surfaces used in the focusing of shock waves for technological needs are known [8]. However, among their disadvantages should be noted that partial usage of the energy of acoustic wave and the problem of it's peripheral sources synchronization, which leads to distortion of the shock wave front ideality and reduces the focusing effectiveness.

Probably, more perspective method of using acoustic waves is their generation by single axial pulse electric discharge with further reflection from an ideal cylindrical surface. This approach can provide better symmetry of compression by convergent acoustic wave both in the gas and in the liquid. Probably, such mechanism can be exploited for scH2O production

In addition, the re-ignition of electrical discharge at the moment of collapse convergent acoustic waves can lead to the plasma temperature increasing due to compression of the discharge channel, as well as the appropriate amplification of acoustic waves after the collapse.

It's clear that plasma-liquid systems (PLS) mentioned above have some sharp differences. Therefore, the first section of this article presents the results of our research on the addition of CO2 to the "TORNADO-LE". And the second section of the article is devoted to investigation of double-impulse system in underwater electric discharge.

### **2. Bioethanol and bioglycerol conversion in "tornado" type plasma-liquid system with the addition of CO2**

#### **2.1. Experimental set up**

The experimental setting is shown in Fig. 1. Its base is a cylindrical quartz chamber (1) with diameter of 90 mm and height of 50 mm. Top (2) and bottom (3) it is hermetically closed with metal flanges. Camera is filled with fluid (4), the level of which has been maintained by the injection pump through the hole (5). Bottom flange is made of stainless steel. The stainless steel T-shaped cylindrical electrode (6), cooled with water, immerses in the liquid through the central hole in the bottom flange. There is a 5 mm thick metal washer on its surface (7) in the middle of which there is a hole in diameter of 10 mm. Sharp corners are rounded. This washer is used for reducing the waves (which have been moving to the quartz wall) amplitude on the liquid surface.

Condensed matter (16) together with the gas from the refrigerator gets to the chamber (17). At the chamber exit (17) there's a flask (18), where gas is gathered for its composition diagnostics by means of mass spectrometry and gas chromatography. Study of plasma parameters is performed by emission spectrometry. The emission spectra registration procedure uses the system which consists of optical fiber, the spectral unit S-150-2-3648 USB, and the computer. Fiber is focusing on the sight line in the middle between the top flange (2) and the surface of

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The spectrometer works in the wavelength range from 200 to 1100 nm. The computer is used in both control measurements process and data processing, received from the spectrometer.

The voltage between the top flange and electrode, immersed in the liquid, is supplied by the power unit "PU". DC voltage provided is up to 7 kV. Two modes of operation have been

**1.** "liquid" cathode (LC) – electrode immersed in the liquid has "minus" and the top flange

Electrode which has "plus" is grounded. Breakdown conditions are controlled by three parameters: the fluid level, the gas flow value and the voltage magnitude between the

**3.** Discharge current varied within Id = 220 ÷ 340 mA (ballast resistance hasn't been used). At first, for the analysis of the plasma-chemical processes kinetics the distilled water (working fluid), and ethanol (ethyl alcohol solution in distilled water with a molar ratio C2H5OH/H2O = 1/9.5), as a hydrocarbon model have been used. As the working gas mixture of air with CO2, in a wide range of air flow and CO2 ratios has been used. The ratio between air and CO2 in the working gas changes in the ranges: CO2/Air = 1/20 ÷ 1/3 for the working fluid C2H5OH/H2O

Plasma component composition and population temperature of the excited electron (*Te*

these components have been determined by the emission spectra. For the temperature population determination of the excited oxygen atoms electron levels the Boltzmann diagram

lines (777.2 nm, 844 nm, 926 nm). Temperature population of excited hydrogen atoms electron levels has been determined by the two lines of 656.3 nm and 486 nm relative intensities.

The effect of the presence of CO2 in the system on the initial gas products has been investigated by means of "TORNADO-LE" current-voltage characteristics with changes in the working gas

emission spectra with the molecules spectra simulated in the SPECAIR program [9]. With help

) levels of plasma components and relative concentrations of

*\** of oxygen atoms has been determined for the three most intense

have been determined by comparing the experimentally measured

*\* ),*

(1/9.5) and CO2/Air = 0/1 ÷ 1/0 (by pure air to pure CO2) - for distilled water.

*\**

the liquid (4).

considered:

vibration (*Tv*

composition. *Tv*

*\**

method has been used [5]. *Te*

*\** and *Tr \**

*)* and rotational (*Tr*

has "plus";

**2.** solid" cathode (SC) - with the opposite polarity.

**2.** Discharge voltage varied within Ud = 2.2 ÷ 2.4 kV;

**1.** Various air flow and CO2 ratio;

electrodes. The several modes of operation have been studied:

The top flange, made from duralumin, contains copper sleeve (13) with a diameter of 20 mm is placed in the center (2), and plays the role of the second electrode. The nozzle with diameter of 4 mm and length of 6 mm is located in the center of the copper sleeve (8). Gas is introduced into the flange (2) through the aperture (9). Gas flow changes the direction at 90 degrees inside the flange and injects tangentially into the channel (10). (10) The gas is rotated in the circular channel. Rotating gas (11) lands on the surface liquid and moves to the central axis of the system, where fells into the quartz cell through the nozzle (14), forming a plasma torch (12). Camera (14), in its turn, plays a role of pyrolytic chamber. Flow rate reaches the maximum value near the nozzle. Due to this, the zone of lower pressure is formed in the center of the gas layer, compared to the periphery. The conical structure appears over the liquid's surface near the system axis (Fig. 1). External static pressure is 1 atm. and internal - 1.2 atm (during discharge burning). Gas from quartz chamber (14) gets into the refrigerator (15), which is cooled with water at room temperature.

**Figure 1.** Schematic set up of the "TORNADO-LE".

Condensed matter (16) together with the gas from the refrigerator gets to the chamber (17). At the chamber exit (17) there's a flask (18), where gas is gathered for its composition diagnostics by means of mass spectrometry and gas chromatography. Study of plasma parameters is performed by emission spectrometry. The emission spectra registration procedure uses the system which consists of optical fiber, the spectral unit S-150-2-3648 USB, and the computer. Fiber is focusing on the sight line in the middle between the top flange (2) and the surface of the liquid (4).

The spectrometer works in the wavelength range from 200 to 1100 nm. The computer is used in both control measurements process and data processing, received from the spectrometer.

The voltage between the top flange and electrode, immersed in the liquid, is supplied by the power unit "PU". DC voltage provided is up to 7 kV. Two modes of operation have been considered:


Electrode which has "plus" is grounded. Breakdown conditions are controlled by three parameters: the fluid level, the gas flow value and the voltage magnitude between the electrodes. The several modes of operation have been studied:


At first, for the analysis of the plasma-chemical processes kinetics the distilled water (working fluid), and ethanol (ethyl alcohol solution in distilled water with a molar ratio C2H5OH/H2O = 1/9.5), as a hydrocarbon model have been used. As the working gas mixture of air with CO2, in a wide range of air flow and CO2 ratios has been used. The ratio between air and CO2 in the working gas changes in the ranges: CO2/Air = 1/20 ÷ 1/3 for the working fluid C2H5OH/H2O (1/9.5) and CO2/Air = 0/1 ÷ 1/0 (by pure air to pure CO2) - for distilled water.

Plasma component composition and population temperature of the excited electron (*Te \* ),* vibration (*Tv \* )* and rotational (*Tr \** ) levels of plasma components and relative concentrations of these components have been determined by the emission spectra. For the temperature population determination of the excited oxygen atoms electron levels the Boltzmann diagram method has been used [5]. *Te \** of oxygen atoms has been determined for the three most intense lines (777.2 nm, 844 nm, 926 nm). Temperature population of excited hydrogen atoms electron levels has been determined by the two lines of 656.3 nm and 486 nm relative intensities.

The effect of the presence of CO2 in the system on the initial gas products has been investigated by means of "TORNADO-LE" current-voltage characteristics with changes in the working gas composition. *Tv \** and *Tr \** have been determined by comparing the experimentally measured emission spectra with the molecules spectra simulated in the SPECAIR program [9]. With help of this program and measured spectra, relative component concentrations in plasma have been determined. Also, the concentration of atomic components has been obtained by calculating the amount of oxygen that fell into a working system with the working gas flow. The hydrogen amount has been received from the electrolysis calculations. The output gas in reforming ethanol has been analyzed by gas chromatography and infrared absorption.

#### **2.2. Results**

The process of discharge ignition occurred as follows: the chamber is filled with liquid to a fixed level (5 mm above the washer). At the next stage a certain amount of gas flow forms the stationary cone from liquid; the voltage applied between the top flange and electrode im‐ mersed in a liquid starts gradually increase. When the voltage reaches a break-out value - *Ub*, a streamer appears for the first time. After that, burning discharge starts in split second, and then voltage decreases and current increases. After a second or two it is stabilized. During this time – static pressure rises inside the chamber from 1 to 1.2 atm. If you maintain the liquid level fixed, then the discharge is quite steady.

The current-voltage characteristics show that adding a small amount of СО<sup>2</sup> (near 20%) to the working gas has no effect on the discharge type in various studied working liquids. In the range of flow ratios CO2/Air from 1/20 to 1/5 characteristics are straight lines. It was observed

**Figure 2.** a) Current-voltage characteristics of the discharge at different ratios of CO2/Air in the working gas. Working liquid - distilled water. Airflow - 55 and 82.5 cm3/s, the flow of CO2 - 4.25, 8.5 and 17 cm3 /sec. b) Current-voltage characteristics of the discharge at the ratio CO2/Air = 1/5 in the working gas. Working liquid – С2Н5ОН/H2O (1/9.5)

(a) (b)

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Typical emission spectra of the plasma are shown in Fig. 3a and Fig. 3b for the cases with the

The emission spectra show that when the working liquid is distilled water, plasma contains the following components: atoms H, O, and hydroxyl OH. In case when the working liquid is С2Н5ОН/H2O solution (1/9.5), plasma has the following components: atoms – N, O, C, Fe, Cr, molecules – OH, CN, NH. The emission spectra shows that the replacement of the working liquid with distilled water with ethanol CN and lower electrode material made of stainless steel (anode) occur in plasma. Occasionally, during discharge burning breakdown may occur

Those breakdowns may occur due to the fact that during the discharge burning, thickness of liquid layer, when the working fluid has a significant share of С2Н5ОН, a current channel is formed through the liquid layer to the metal electrode. And in the case of distilled water plasma channel discharge ends near the surface of the liquid. It may indicate the presence of

It was observed that the increase of CO2 in the working gas (CO2/air > 0.3) leads to an increase in the intensity of hydrogen and oxygen radiation lines (H and O) at the time when the intensity of the molecular component (OH) radiation, within the error, is stable (I = 300 mA, U = 1.9-2.4

Fig. 4 shows the ratio of the hydrogen (Hα λ = 656.3 nm) and oxygen (O, λ = 777.2 nm) radiation intensity to the highest point of band hydroxyl (OH, λ = 282.2 nm) small intensity at different

because of the possible reabsorption. (I = 300 mA, U = 2 – 2.2 kV). In the case of distilled water

/sec).

/s). High intensity bands haven't been used in the calculations

/s, the flow of

/sec, the flow of CO2 - 4.25 - 85 cm<sup>3</sup>

ratios of CO2/air (I = 300 mA, U = 1.9 – 2.4 kV, air flow - 27.5, 55 and 82.5 cm<sup>3</sup>

that the increasing of СО2 share in working gas causes discharge voltage supply rise.

distilled water as the working liquid and the solution of С2Н5ОН/H2O (1/9.5).

in С2Н5ОН/H2O layer solution (1/9.5).

solution. Airflow - 82.5 cm3/s, the flow of CO2 - 17 cm3/s.

large liquid surface charge.

kV, air flow 0 - 82.5 cm3

CO2 - 4.25, 8.5, 17, 42.5 and 85 cm<sup>3</sup>

Liquid layer thickness of 5 mm has been chosen because that is the minimum liquid thickness in which the discharge burns between the liquid surface and the top flange. If the thickness is smaller plasma pushes the water toward the electrode immersed in the liquid and the discharge starts burning between two metal electrodes. Discharge goes into the arc regime. When the thickness of the distilled water layer above the washer is 5 mm (in the case of air flow only) break voltage reaches 4.5 kV and for a CO2 flow - 6 kV. It is known [10], this increase in break-out voltage derives from the appearance of an additional loss channel of electrons – due to their sticking onto CO2 molecules. This sticking has dissociative character and it is accompanied by the energy expense.

For example, the threshold reaction with CO2 is 3.85 eV. Therefore CVC in pure CO2 is decreased (Fig. 2). When the thickness of the С2Н5ОН/H2O (1/9.5) solution layer above the washer is 5 mm (in the case of air flow only) the break voltage is 5.5 kV, and for the air flow mixture with CO2 (CO2/Air = 1/3) – 6.5 kV. Adding CO<sup>2</sup> to the air leads to the increase in the break-out voltage value. Adding ethanol to distilled water (С2Н5ОН/H2O = 1/9.5) results in the increase of break voltage on 1 kV. Power supply unit provides maximum voltage of 7 kV. Increasing the thickness of the fluid layer above the washer (> 5 mm) leads to the increase of the break-out voltage value. There is no discharge ignition with a break-out voltage value of more than 7 kV. Therefore, 5 mm thickness of the liquid layer above the surface immersed in a liquid metal electrode (washer) has been chosen as the optimum one.

The current-voltage characteristics of the discharge are shown for the SC mode (Fig. 2 a; 2b). The cell has been filled with distilled water (Fig. 2a) or bioethanol (Fig. 2b).

The "tornado" type reverse vortex gas flow is formed by gas flow, which is a mixture of air with СО2 in varying proportions. Ratio of CO2/Air is changed in the range from 1/20 to 1/3, and in the case of ethanol and 1/0 in the case of water. Current varied in the range from 230 to 400 mA. The initial level of the working liquid is the same in all cases.

**Figure 2.** a) Current-voltage characteristics of the discharge at different ratios of CO2/Air in the working gas. Working liquid - distilled water. Airflow - 55 and 82.5 cm3/s, the flow of CO2 - 4.25, 8.5 and 17 cm3 /sec. b) Current-voltage characteristics of the discharge at the ratio CO2/Air = 1/5 in the working gas. Working liquid – С2Н5ОН/H2O (1/9.5) solution. Airflow - 82.5 cm3/s, the flow of CO2 - 17 cm3/s.

The current-voltage characteristics show that adding a small amount of СО<sup>2</sup> (near 20%) to the working gas has no effect on the discharge type in various studied working liquids. In the range of flow ratios CO2/Air from 1/20 to 1/5 characteristics are straight lines. It was observed that the increasing of СО2 share in working gas causes discharge voltage supply rise.

Typical emission spectra of the plasma are shown in Fig. 3a and Fig. 3b for the cases with the distilled water as the working liquid and the solution of С2Н5ОН/H2O (1/9.5).

The emission spectra show that when the working liquid is distilled water, plasma contains the following components: atoms H, O, and hydroxyl OH. In case when the working liquid is С2Н5ОН/H2O solution (1/9.5), plasma has the following components: atoms – N, O, C, Fe, Cr, molecules – OH, CN, NH. The emission spectra shows that the replacement of the working liquid with distilled water with ethanol CN and lower electrode material made of stainless steel (anode) occur in plasma. Occasionally, during discharge burning breakdown may occur in С2Н5ОН/H2O layer solution (1/9.5).

Those breakdowns may occur due to the fact that during the discharge burning, thickness of liquid layer, when the working fluid has a significant share of С2Н5ОН, a current channel is formed through the liquid layer to the metal electrode. And in the case of distilled water plasma channel discharge ends near the surface of the liquid. It may indicate the presence of large liquid surface charge.

It was observed that the increase of CO2 in the working gas (CO2/air > 0.3) leads to an increase in the intensity of hydrogen and oxygen radiation lines (H and O) at the time when the intensity of the molecular component (OH) radiation, within the error, is stable (I = 300 mA, U = 1.9-2.4 kV, air flow 0 - 82.5 cm3 /sec, the flow of CO2 - 4.25 - 85 cm<sup>3</sup> /sec).

Fig. 4 shows the ratio of the hydrogen (Hα λ = 656.3 nm) and oxygen (O, λ = 777.2 nm) radiation intensity to the highest point of band hydroxyl (OH, λ = 282.2 nm) small intensity at different ratios of CO2/air (I = 300 mA, U = 1.9 – 2.4 kV, air flow - 27.5, 55 and 82.5 cm<sup>3</sup> /s, the flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm<sup>3</sup> /s). High intensity bands haven't been used in the calculations because of the possible reabsorption. (I = 300 mA, U = 2 – 2.2 kV). In the case of distilled water

(a) (b)

**Figure 4.** The ratio of the radiation intensity of hydrogen (H<sup>α</sup> λ = 656.3 nm) and oxygen (O, λ = 777.2 nm) to the peak of the band hydroxyl (OH λ = 282,2 nm) at different ratio CO2/Air in the working gas. Working liquid - distilled water

In calculating the relative concentration ratio of hydrogen to oxygen from the emission spectra, it was observed that the hydrogen concentration is two times as much of the oxygen concen‐ tration for the case of distilled water as the working liquid - (I = 300 mA, U = 1.9 – 2.4 kV, airflow

/sec, the flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm3

much when the working liquid is С2Н5ОН/H2O solution (1/9.5) (I = 300 mA, U = 2 - 2.2 kV, air

the calculations, these components production by means of electrolysis and their extraction from the working gas, the oxygen concentration exceeds the average hydrogen concentration in three orders of magnitude, unless the case when the pure CO2 is used as a working gas.

It should be noted that the addition of CO2 reduces the discharge stability, especially in the case of bioethanol. In determination of the temperature population excited electron levels of plasma atomic component the most intense lines (spectra with the smallest possible accumu‐ lation in the experiment measurement of 500 ms) have been used, according to the discharge

Temperature of excited hydrogen electron population levels is determined by the relative intensities (two lines of 656 nm and 486 nm). For the case where the working liquid is distilled

of distilled water. The three most intense lines (777.2 nm, 844 nm, 926 nm) are used in this

Temperatures of OH excited vibrate and rotational population levels have been determined by comparing the experimentally measured emission spectra with the molecular spectra modeled in The SPECAIR program. In the case when the working liquid is distilled water,

(OH) = 3000 ± 1000 K, *Tv*

(H) = 5500 ± 700 K (I = 300 mA, U = 1.9-2.4 kV, air flow - 27.5, 55 and 82.5 cm<sup>3</sup>

/s) and as for the bioethanol *Te*

(O) has been defined by the Boltzmann diagrams method, in the case

\*

/sec, the flow of CO2 - 4.25, 8.5 and 17 cm3

burning particularity. Also, it affects the parameters determination accuracy.

/sec), and ten times as

/s, the

/

(H) = 6000 ± 500 K -

/sec). However, according to

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\*

/s, the flow of CO2 - 4.25, 8.5 and 17 cm3

(OH) = 4000 ± 1000 K (I = 300 mA,

(a) I = 300 mA, U = 1.9 – 2.4 kV and bioethanol (b) I = 300 mA, U = 2 -2.2 kV.


flow - 55 and 82.5 cm3

water – *Te*

\*

s). Also, the oxygen *Te*

method. So, we have *Te*

appropriate temperatures are: *Tr*

flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm3

\*

\*

(I = 300 mA, U = 2 – 2.2 kV, air flow - 55 and 82.5 cm3

(O) = 4700 ± 700 K.

\*

**Figure 3.** a) Emission spectrum of the plasma in TORNADO-LE plasma-liquid system, where the working liquid is distil‐ led water. Working gas - a mixture of СО2/air = 1/0, Id = 300 mA, U = 2.2 kV, the flow of CO2 - 85 cm3/s and СО2/air = 1/20, Id = 300 mA, U = 1.9 -2.0 kV, air flow - 82.5 cm3/s, the flow of CO2 - 4.25 cm3/s. b) Emission spectrum of the plasma in the TORNADO-LE plasma-liquid system, where the working fluid is bioethanol. Working gas - a mixture of СО2/air = 1/20, Id = 300 mA, U = 2 kV, air flow - 82.5 cm3/sec, the flow of CO2 - 4.25 cm3/sec.

(Fig. 4a), results are presented for the three air flows - 27.5, 55 and 82.5 cm3 /s and five CO2 streams - 4.25, 8.5, 17, 42.5 and 85 cm3 /s (I = 300 mA , U = 1.9 – 2.4 kV). Air and CO2 flows are variated so that the total flow compiles similar values and achieves ratios of CO2/air in a wide range from 1/20 to 1/0.

**Figure 4.** The ratio of the radiation intensity of hydrogen (H<sup>α</sup> λ = 656.3 nm) and oxygen (O, λ = 777.2 nm) to the peak of the band hydroxyl (OH λ = 282,2 nm) at different ratio CO2/Air in the working gas. Working liquid - distilled water (a) I = 300 mA, U = 1.9 – 2.4 kV and bioethanol (b) I = 300 mA, U = 2 -2.2 kV.

In calculating the relative concentration ratio of hydrogen to oxygen from the emission spectra, it was observed that the hydrogen concentration is two times as much of the oxygen concen‐ tration for the case of distilled water as the working liquid - (I = 300 mA, U = 1.9 – 2.4 kV, airflow - 27.5, 55 and 82.5 cm3 /sec, the flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm3 /sec), and ten times as much when the working liquid is С2Н5ОН/H2O solution (1/9.5) (I = 300 mA, U = 2 - 2.2 kV, air flow - 55 and 82.5 cm3 /sec, the flow of CO2 - 4.25, 8.5 and 17 cm3 /sec). However, according to the calculations, these components production by means of electrolysis and their extraction from the working gas, the oxygen concentration exceeds the average hydrogen concentration in three orders of magnitude, unless the case when the pure CO2 is used as a working gas.

It should be noted that the addition of CO2 reduces the discharge stability, especially in the case of bioethanol. In determination of the temperature population excited electron levels of plasma atomic component the most intense lines (spectra with the smallest possible accumu‐ lation in the experiment measurement of 500 ms) have been used, according to the discharge burning particularity. Also, it affects the parameters determination accuracy.

Temperature of excited hydrogen electron population levels is determined by the relative intensities (two lines of 656 nm and 486 nm). For the case where the working liquid is distilled water – *Te* \* (H) = 5500 ± 700 K (I = 300 mA, U = 1.9-2.4 kV, air flow - 27.5, 55 and 82.5 cm<sup>3</sup> /s, the flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm3 /s) and as for the bioethanol *Te* \* (H) = 6000 ± 500 K - (I = 300 mA, U = 2 – 2.2 kV, air flow - 55 and 82.5 cm3 /s, the flow of CO2 - 4.25, 8.5 and 17 cm3 / s). Also, the oxygen *Te* \* (O) has been defined by the Boltzmann diagrams method, in the case of distilled water. The three most intense lines (777.2 nm, 844 nm, 926 nm) are used in this method. So, we have *Te* \* (O) = 4700 ± 700 K.

Temperatures of OH excited vibrate and rotational population levels have been determined by comparing the experimentally measured emission spectra with the molecular spectra modeled in The SPECAIR program. In the case when the working liquid is distilled water, appropriate temperatures are: *Tr* \* (OH) = 3000 ± 1000 K, *Tv* \* (OH) = 4000 ± 1000 K (I = 300 mA, U = 1.9-2.4 kV, air flow - 27.5, 55 and 82.5 cm3 / s, the flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm3 /s). Also, population temperatures of vibration and rotational levels for OH and CN have been determined in case of C2N5ON/H2O (1/9.5) solution as the working liquid, they are: *Tr* \* (OH) = 3500 ± 500 K, *Tv* \* (OH) = 4000 ± 500 K, *Tr* \* (CN) = 4000 ± 500 K, *Tv* \* (CN) = 4500 ± 500 K) (I = 300 mA, U = 2 - 2.2 kV, air currents - 55 and 82.5 cm3 /s, the flow of CO2 - 4.25, 8.5 and 17 cm3 /s). Temperatures for other molecular components haven't been determined because of their bands low intensity.

During the study, it turned out that the addition of CO2 weakly affects the population temperature of excited electron, vibration and rotational levels of plasma components (Fig. 5) (I = 300 mA, U = 1.9 - 2.4 kV, air flow - 27.5, 55 and 82.5 cm3 /s, the flow of CO2 - 4.25, 8.5, 17, 42.5 and 85 cm3 /s). Weak tendency to temperature decrease has been observed, but these changes do not exceed the error.

**Figure 6.** Gas chromatography comparison of bioethanol conversion output products with and without the addition

**Figure 7.** Gas chromatography comparison of bioethanol conversion output products by adding different amounts of

The ethanol solution consumption for the SC mode with current of 300 mA and air flow of 55

Accordingtothegaschromatography,inthestudiedcorrelations rangeofCO2/Air, syn-gas ratio ([H2]/[CO]), changes slightly – look at Fig. 8. Measurements were made by two air streams of 55

Besides the gas chromatography, the output gas composition has been studied by means of infrared spectrophotometry (IRS). Fig. 9 shows a typical IRS spectrum of the output gas. In the SC mode (current 300 mA, voltage 2 kV) the working liquid is ethyl alcohol and distilled water

mixture. Research has been carried out in a ditch with a length of 10 cm and a diameter of 4 cm. Pressure inside the ditch has been 1 atm. The ditch walls have been made of BaF2.

/s and CO2 of 17 cm3

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/s mixture - 10 ml/min.

/s) and CO2 (4.25 cm3

/s)

/s; I = 300 mA, U = 2 – 2.2 kV.

/ equals 6 ml/min, and for the air flow of 82.5 cm3

/s and three CO2 streams of – 4.25, 8.5 and 17 cm3

mixture (С2Н5ОН/H2O = 1/9.5), and the working gas – air (82.5 cm3

of CO2.

CO2.

cm3

and 82.5 cm3

**Figure 5.** Population temperatures of excited electron, vibration and rotational levels of plasma components at differ‐ ent ratio of CO2/Air in the working gas. Working liquids - distilled water (a) and ethanol (b)

Fig. 6–7. shows the results of gas chromatography bioethanol conversion output products. Results are presented for two air streams 55 and 82.5 cm3 /s + three CO2 streams: 4.25, 8.5 and 17 cm3 /s (I = 300 mA, U = 2 – 2.2 kV). CO2/Air ratio in the range from 1/20 to 1/3 has been changing exactly this way. Selection of gas into the flask has been taken place at the refrigerator output. The flask has been previously pumped by the water-jet pump to the pressure of saturated water vapor (23 mm Hg).

Fig. 6 shows the gas chromatography comparison of bioethanol conversion output products with and without the addition of CO2. The air flow is constant – 55 cm3 /s, in case of CO2/Air = 1/3 – 17 cm3 /s of CO2 has been added to the air (the total flow has been increased, which may explain the decrease in the percentage of nitrogen at a constant air flow; I = 300 mA, U = 2 - 2.2 kV). This histogram shows that adding of carbon dioxide leads to a significant increase of the H2 component percentage, CO (syn-gas) and CH4 in the output gas. This may indicate that the addition of CO2 during the ethanol reforming increases the conversion efficiency, because CO2 plays a burning retarder role.

**Figure 6.** Gas chromatography comparison of bioethanol conversion output products with and without the addition of CO2.

**Figure 7.** Gas chromatography comparison of bioethanol conversion output products by adding different amounts of CO2.

The ethanol solution consumption for the SC mode with current of 300 mA and air flow of 55 cm3 / equals 6 ml/min, and for the air flow of 82.5 cm3 /s and CO2 of 17 cm3 /s mixture - 10 ml/min.

Accordingtothegaschromatography,inthestudiedcorrelations rangeofCO2/Air, syn-gas ratio ([H2]/[CO]), changes slightly – look at Fig. 8. Measurements were made by two air streams of 55 and 82.5 cm3 /s and three CO2 streams of – 4.25, 8.5 and 17 cm3 /s; I = 300 mA, U = 2 – 2.2 kV.

Besides the gas chromatography, the output gas composition has been studied by means of infrared spectrophotometry (IRS). Fig. 9 shows a typical IRS spectrum of the output gas. In the SC mode (current 300 mA, voltage 2 kV) the working liquid is ethyl alcohol and distilled water mixture (С2Н5ОН/H2O = 1/9.5), and the working gas – air (82.5 cm3 /s) and CO2 (4.25 cm3 /s) mixture. Research has been carried out in a ditch with a length of 10 cm and a diameter of 4 cm. Pressure inside the ditch has been 1 atm. The ditch walls have been made of BaF2.

**Figure 8.** Syn-gas ratio of bioethanol conversion output products for various ratios of CO2/Air in the range between 0/1 - 1/3.

**Figure 10.** Dependence of the normalized maximum intensity peaks (2000-2250 cm-1) transmission of CO in the syn-

Plasma provides gas generation, which contains a certain amount of the syn-gas. The energy

where *Pd* - power that has been embedded into the discharge, *t* – production time of gas volume unit during the reforming process. Electrical energy transformation coefficient α has been

> *s p Q Q* a

where *Qs* - energy that is released during the complete combustion of syngas (obtained in the

Electrical energy transformation coefficient α has value of 0.81 for the "TORNADO-LE" with

1/3) gives the value of α = 1,01. System electrical parameters are as follows: I = 300 mA, U = 2

In the model of calculations was assumed that the discharge is homogeneous over the entire volume. It is justified at zero approximation, because the time of gas mixing in the radial direction is less than the times of characteristic chemical reactions. Also we neglect the processes in the transitive zone between the discharge to post-discharge. Thus, the time of gas

, *Q Pt p d* = (1)

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= (2)

/s. And the CO2 addition (the ratio of CO2/air =

needed for this plasma support (*Qp*) has been calculated by the following formula:

gas, depending on the concentration of CO according to gas chromatography data.

calculated by the formula:

reforming process).

**2.3. Model and calculations**

– 2.2 kV.

an ethanol solution and pure air flow 55 cm3

Fig. 10 shows the dependence of the CO transmission standardized maximum intensity peaks (2000 - 2250 cm-1) in the syn-gas, depending on the CO concentration according to gas chro‐ matography results. Standardization has been conducted for the maximum intensity value of the CO transmission peak bandwidth at the SC mode with the current of 300 mA, voltage - 2 kV, the mixture of ethyl alcohol and distilled water (С2Н5ОН/H2O = 1/9.5) as the working liquid, and the mixture of air (82.5 cm3 /s) and CO2 (4.25 cm3 /s), as the working gas.

According to IR spectrophotometry CO fraction in the synthesis gas is practically the same. According to gas chromatography CO fraction in the synthesis gas in the different operation modes stays on the same level as well (the changes are in the range of 1%). So IR spectropho‐ tometry can be used determine the composition of synthesis gas under ethanol reforming.

**Figure 9.** The SC mode (current 300 mA, voltage 2 kV) the working liquid is ethyl alcohol and distilled water mixture (С2Н5ОН/H2O = 1/9.5), the working gas – air (82.5 cm<sup>3</sup>/s) and CO2 (4.25 cm<sup>3</sup>/s) mixture

**Figure 10.** Dependence of the normalized maximum intensity peaks (2000-2250 cm-1) transmission of CO in the syngas, depending on the concentration of CO according to gas chromatography data.

Plasma provides gas generation, which contains a certain amount of the syn-gas. The energy needed for this plasma support (*Qp*) has been calculated by the following formula:

$$Q\_p = P\_d t\_\prime \tag{1}$$

where *Pd* - power that has been embedded into the discharge, *t* – production time of gas volume unit during the reforming process. Electrical energy transformation coefficient α has been calculated by the formula:

$$
\alpha = \frac{\mathbb{Q}\_s}{\mathbb{Q}\_p} \tag{2}
$$

where *Qs* - energy that is released during the complete combustion of syngas (obtained in the reforming process).

Electrical energy transformation coefficient α has value of 0.81 for the "TORNADO-LE" with an ethanol solution and pure air flow 55 cm3 /s. And the CO2 addition (the ratio of CO2/air = 1/3) gives the value of α = 1,01. System electrical parameters are as follows: I = 300 mA, U = 2 – 2.2 kV.

#### **2.3. Model and calculations**

In the model of calculations was assumed that the discharge is homogeneous over the entire volume. It is justified at zero approximation, because the time of gas mixing in the radial direction is less than the times of characteristic chemical reactions. Also we neglect the processes in the transitive zone between the discharge to post-discharge. Thus, the time of gas pumping through the transition region is too short for the chemical reactions to have a sufficient influence on the concentration of neutral components.

of concentrations of all species. This allows us to stop the calculations in the discharge region and to investigate the kinetics in the post-discharge region. System (3) is solved without accounting for the last three terms on the time interval without the plasma. The calculations

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The full mechanism developed for this experimental work is composed of 30 components and 130 chemical reactions between them and its closed to [11]. The charged particles (electrons and ions) are ignored in the mechanism, because of low degree of ionization of the gas (~ 10−6 – 10−5). Nitrogen acts as the third body in the recombination and thermal dissociation reactions. In the non-equilibrium plasma almost the entire energy is deposited into the electron compo‐ nent. The active species, generated in the electron–molecular processes, lead to chain reactions

Numerical simulation of kinetics showed that the main channels of H2 generation in the plasma were ethanol abstraction for the first 10–100*μ*s, and hydrocarbon abstraction afterwards. Additionally, the conditions when the reaction between H2O and hydrogen atoms was the main channel of H2 production were found. A kinetic mechanism, which adequately described the chemistry of the main components, was proposed. The model did not account for nitrogencontaining species, and nitrogen was considered only as a third body in recombination and dissociation reactions. The comparison between experiments and calculations showed that the mechanism can adequately describe the concentrations of the main components (H2, CO, CO2,

**Figure 11.** The dependence of the reaction main products of the flow rate of CO2 (inside discharge), T = 2023 K

are terminated when the molecular oxygen concentration reaches zero level.

with ethanol molecules.

CH4, C2H4, C2H6, and C2H2).

The total time of calculation is divided into two time intervals: the first one is the calculation of the kinetic processes of fast generation of active atoms and radicals in the discharge region. Those components accelerate the formation of molecular hydrogen, carbon oxides and production of other hydrocarbons. The second time interval is the oxidation of the gas mixture in the post-discharge region as a result of the high gas temperature and the presence of O and OH. These components remain in the mixture after the dissociation of water and oxygen molecules by electron impacts in the plasma. The oxidation of generated hydrocarbons has a noticeable influence on kinetics in the investigated mixture due to the high gas temperature.

Under the aforementioned conditions, the characteristic time of oxidation is approximately equal to the air pumping time through the discharge region (~10−3–10−2 s). The following system of kinetic equations is used in order to account for the constant air pumping through the system:

$$\frac{dN\_i}{dt} = \mathbf{S}\_{ei} + \sum\_{j} k\_{ij} \mathbf{N}\_j + \sum\_{j,l} k\_{ijl} \mathbf{N}\_j \mathbf{N}\_l + \dots + \mathbf{K}\_i - \frac{\mathbf{G}}{V} \mathbf{N}\_i - k \mathbf{N}\_i \tag{3}$$

*Ni* , *Nj* , *Nl* in the equation (3) are the concentrations of molecules and radicals; *kij, kiml* are the rate constants of the processes for the *i-*th component. The rates of electron–molecule reactions *S*e*<sup>i</sup>* are connected with discharge power and discharge volume. The last three terms in equation (1) describe the constant inflow and outflow of gas from the discharge region. The term *Ki* is the inflow of molecules of the primary components (nitrogen, oxygen, carbon dioxide, water and ethanol) into the plasma, G/V*Ni* and *kNi* are the gas outflow as the result of air pumping and the pressure difference between the discharge region and the atmosphere. In order to define the initial conditions, the ethanol/water solution is assumed to be an ideal solution. Therefore, the vapor concentrations are linear functions of the ethanol-to-water ratio in the liquid. The evaporation rates *Ki* of C2H5OH and H2O are calculated from the measured liquids' consumption. The inflow rates *Ki* of nitrogen and oxygen are calculated by the rate of air pumping through the discharge region:

$$K\_i = \frac{G}{V} N\_i^0 \tag{4}$$

where *N*<sup>0</sup> *i* correspond to [N2] and [O2] in the atmospheric pressure air flow.

The gas temperature in the discharge region is taken to be constant in the model. In reality, the gas temperature *T* is dependent on the gas pumping rate and the heat exchange with the environment. Therefore, in order to take into account those influences, *T* is varied in the interval 800–2500K (similarly to the experimentally obtained temperature spread). After ~10−2 s, the balance between the generation and decomposition of the components leads to saturation of concentrations of all species. This allows us to stop the calculations in the discharge region and to investigate the kinetics in the post-discharge region. System (3) is solved without accounting for the last three terms on the time interval without the plasma. The calculations are terminated when the molecular oxygen concentration reaches zero level.

The full mechanism developed for this experimental work is composed of 30 components and 130 chemical reactions between them and its closed to [11]. The charged particles (electrons and ions) are ignored in the mechanism, because of low degree of ionization of the gas (~ 10−6 – 10−5). Nitrogen acts as the third body in the recombination and thermal dissociation reactions. In the non-equilibrium plasma almost the entire energy is deposited into the electron compo‐ nent. The active species, generated in the electron–molecular processes, lead to chain reactions with ethanol molecules.

Numerical simulation of kinetics showed that the main channels of H2 generation in the plasma were ethanol abstraction for the first 10–100*μ*s, and hydrocarbon abstraction afterwards. Additionally, the conditions when the reaction between H2O and hydrogen atoms was the main channel of H2 production were found. A kinetic mechanism, which adequately described the chemistry of the main components, was proposed. The model did not account for nitrogencontaining species, and nitrogen was considered only as a third body in recombination and dissociation reactions. The comparison between experiments and calculations showed that the mechanism can adequately describe the concentrations of the main components (H2, CO, CO2, CH4, C2H4, C2H6, and C2H2).

$$\mathbf{1} = 2023 \text{ к}$$

**Figure 11.** The dependence of the reaction main products of the flow rate of CO2 (inside discharge), T = 2023 K

However, it should be noted that with the increase in temperature to 2523 K leads to the fact that the output of the reactor is not observed almost no light hydrocarbons. They simply "fall apart" and burned. That leaves the most stable elements such as H2O, N2, CO2. This sug‐ gests that the increase in temperature up to these values is not advisable because of the de‐ crease in the yield of useful products (see Fig. 11 and Fig. 12a,b).

Other model hydrocarbon is bioglycerol (crude glycerol) which is a byproduct of the biodiesel manufacture. Biodiesel is a popular alternative fuel. It is carbon neutral, has emissions equivalent or below diesel, is biodegradable, non-toxic, and is significantly cheaper to manufacture than its petroleum equivalent. However there is one significant drawback: for every 10 gallons of biodiesel produced, roughly 1 gallon of bioglycerol is

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Biodiesel is produced by mixing vegetable oil and potassium hydroxide KOH. Therefore, the large-scale production of environmentally friendly and renewable fuel may lead to possible bioglycerol accumulation in large quantities, which, in turn, can cause environmental prob‐ lems, as it is comparably bad fuel. In addition, it has a rather large viscosity of 1.49 Pa•s, which is larger for almost three orders of magnitude than ethanol and water viscosity. The solution to this problem would be "TORNADO-LE" usage for bioglycerol reforming. Pure glycerol chemical formula is C3H5(OH)3. However, bioglycerol contains various impurities (including

Fig. 13 shows a photograph of burning discharge, where the working liquid is bioglycerol and working gas - air. Research is conducted by the SC polarity, because this mode has lowest

**Figure 13.** Photo of the combustion discharge in which the working liquid is bioglycerol and working gas - air.

Fig. 14 shows the typical emission spectrum of the plasma discharge in a "TORNADO-LE" where the working liquid is bioglycerol doped with alkali. It is registered at a current of 300

created as a byproduct.

a set of alkali).

liquid consumption.

**Figure 12.** a). The dependence of the reaction main products of the flow rate of CO2 (after discharge), T = 2023 K. b). The dependence of the reaction main products of the flow rate of CO2 (after discharge), T = 2023 K

These calculations are based in good correspondence with the experimental data (see Fig. 8).

Other model hydrocarbon is bioglycerol (crude glycerol) which is a byproduct of the biodiesel manufacture. Biodiesel is a popular alternative fuel. It is carbon neutral, has emissions equivalent or below diesel, is biodegradable, non-toxic, and is significantly cheaper to manufacture than its petroleum equivalent. However there is one significant drawback: for every 10 gallons of biodiesel produced, roughly 1 gallon of bioglycerol is created as a byproduct.

Biodiesel is produced by mixing vegetable oil and potassium hydroxide KOH. Therefore, the large-scale production of environmentally friendly and renewable fuel may lead to possible bioglycerol accumulation in large quantities, which, in turn, can cause environmental prob‐ lems, as it is comparably bad fuel. In addition, it has a rather large viscosity of 1.49 Pa•s, which is larger for almost three orders of magnitude than ethanol and water viscosity. The solution to this problem would be "TORNADO-LE" usage for bioglycerol reforming. Pure glycerol chemical formula is C3H5(OH)3. However, bioglycerol contains various impurities (including a set of alkali).

Fig. 13 shows a photograph of burning discharge, where the working liquid is bioglycerol and working gas - air. Research is conducted by the SC polarity, because this mode has lowest liquid consumption.

**Figure 13.** Photo of the combustion discharge in which the working liquid is bioglycerol and working gas - air.

Fig. 14 shows the typical emission spectrum of the plasma discharge in a "TORNADO-LE" where the working liquid is bioglycerol doped with alkali. It is registered at a current of 300 mA, voltage – 2 kV, air flow – 110 cm3 /s. Optical fiber is oriented on the sight line, parallel to the liquid surface in the middle of the discharge gap. The distance from the liquid surface to the top flange equals 10 mm.

Emission spectrum (Fig. 14) is normalized to the maximum Na doublet (588.99 nm, 589.59 nm). It contains K (404.41 nm, 404.72 nm, 766.49 nm, 769.89 nm), Na (588.99 nm, 589.59 nm), Ca (422.6 nm) lines, and a part of continuous spectrum, which indicates that the there's a soot in the discharge. Temperature, which is defined by the plasma continuous emission spectrum is 2700 ± 100 K.

With infrared transmission spectra one can see that the transition to bioglycerol increases the amount of such components as CO2 (2250-2400 cm-1), CO (2000-2250 cm-1), CH4 (3025-3200

**Figure 15.** Plasma emission spectrum in the case when the working gas is a mixture SO2/Air = 1/5 (air flow - 82.5

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cm3/s, the CO2 flow - 17 cm3/s), Id = 300 mA, U = 600 V and calculated spectra of blackbody radiation)

Electrical energy is added to the "TONADO-LE" plasma-liquid system in the form of plasma power. Plasma acts as a catalyst and thus this power should be controlled. In addition to electric energy for plasma we incorporate hydrocarbon (ethanol or bioglycerol) as an input to the system. These hydrocarbons are raw material for syn-gas generation but they are also a fuel which has some energy associated with it. So, we input some energy to the system (hydrocar‐

Carbon dioxide adding leads to a significant increase the percentage of H2 + CO (syn-gas) and CH4 components in the exhaust. This may indicate that the CO2 addition under the ethanol reforming increases the conversion efficiency, because CO2 plays a role of the retarder in the

The transmission spectra of infrared radiation indicate that the exhaust gas obtained by ethanol solution conversion, contains such components as CO, CO2, CH4, C2H2. It was found that CO2 adding reduces the CH4 and C2H2 amount, but does not affect the amount of producted

The possibility of hydrocarbons reforming, which have considerable viscosity (bioglycerol) in the "TORNADO-LE" is shown. This gives a possibility to avoid environmental problems due

The α coefficient [see (2)] in bioglycerol reforming is higher than ethanol reforming at the same ratios of CO2/Air in the input gas. This may be connected with the lower power consumption

bon + electricity) and we get syn-gas, which is potentially a source of energy as well.

system by reducing the intensity of the conversion components combustion.

to the bioglyсerol accumulation during biodiesel production.

cm-1), C2H2 (3200-3350 cm-1).

**2.4. Discussions**

CO.

**Figure 14.** Typical emission spectrum of the plasma discharge, which burns in a mixture of air and bioglycerol / alkali.

The K, Na, Ca elements presence in the discharge gap complicates the plasma kinetics numeric modeling of the bioglycerol reform process. The gas flow rate at the system outlet is 190 cm3 /s, i.e. by 80 cm3 /s larger than the initial (110 cm3 /s), which indicates bioglycerol reforming to the syn-gas. Liquid flow is 5 ml/min. Change of the CO2 share in the working gas weakly affects the spectrum appearance.

Based on the continuous nature of the plasma emission spectra, we compared the experimental results with the calculated spectra of the blackbody radiation. Calculations have been per‐ formed by using Planck's formula.

Fig. 15 shows the computational grid with step of 200-300 K in the temperature range from 2500 K to 3500 K and the plasma emission spectrum in the case of bioglycerol, as a working fluid (air flow - 82.5 cm3 /s, the flow of CO2 - 17 cm3 /s, CO2/Air = 1/5, Id = 300 mA, U = 600 V). All spectra are normalized to the intensity, which is located at a wavelength of 710 nm.

The data in Fig. 15 show that the plasma emission spectrum coincides with the calculated by the Planck formula for the temperature T = 2800 ± 200 K. Since bioglycerol contains alkali metals, which represent an aggressive environment, the gas chromatography can't be used. Therefore, in order to determine the gas composition, formed the bioglycerol reformation IR and mass spectrometry have been used.

**Figure 15.** Plasma emission spectrum in the case when the working gas is a mixture SO2/Air = 1/5 (air flow - 82.5 cm3/s, the CO2 flow - 17 cm3/s), Id = 300 mA, U = 600 V and calculated spectra of blackbody radiation)

With infrared transmission spectra one can see that the transition to bioglycerol increases the amount of such components as CO2 (2250-2400 cm-1), CO (2000-2250 cm-1), CH4 (3025-3200 cm-1), C2H2 (3200-3350 cm-1).

#### **2.4. Discussions**

Electrical energy is added to the "TONADO-LE" plasma-liquid system in the form of plasma power. Plasma acts as a catalyst and thus this power should be controlled. In addition to electric energy for plasma we incorporate hydrocarbon (ethanol or bioglycerol) as an input to the system. These hydrocarbons are raw material for syn-gas generation but they are also a fuel which has some energy associated with it. So, we input some energy to the system (hydrocar‐ bon + electricity) and we get syn-gas, which is potentially a source of energy as well.

Carbon dioxide adding leads to a significant increase the percentage of H2 + CO (syn-gas) and CH4 components in the exhaust. This may indicate that the CO2 addition under the ethanol reforming increases the conversion efficiency, because CO2 plays a role of the retarder in the system by reducing the intensity of the conversion components combustion.

The transmission spectra of infrared radiation indicate that the exhaust gas obtained by ethanol solution conversion, contains such components as CO, CO2, CH4, C2H2. It was found that CO2 adding reduces the CH4 and C2H2 amount, but does not affect the amount of producted CO.

The possibility of hydrocarbons reforming, which have considerable viscosity (bioglycerol) in the "TORNADO-LE" is shown. This gives a possibility to avoid environmental problems due to the bioglyсerol accumulation during biodiesel production.

The α coefficient [see (2)] in bioglycerol reforming is higher than ethanol reforming at the same ratios of CO2/Air in the input gas. This may be connected with the lower power consumption on the plasma generation in case of bioglycerol reforming. Bioglycerol contains alkaline dash, which increases the bioglycerol conductivity. Bioglycerol reforming products contain mainly CO and hydrocarbons CH4, C2H2, which also gives some contribution to energy yield.

as in static mode (no flow), and dynamic one (with flow ~ 15 cm3

only one capacitor is discharged with a frequency of 0 - 100 Hz.

(source diameter 8 mm) located near the inner wall of the cylinder at a distance of 130 mm from the discharge gap (Fig. 16). The working fluids are: the tap water (with and without flow),

The main feature of electrical scheme for pulsed power feeding of discharge in a liquid is usage of two independent capacitors which are supplied two independent sources of power (1 kW). Pulsed discharge realized in two modes: single and double pulses. In the single pulse mode

Double pulse mode is realized as follows: one capacitor discharges in the interelectrode gap through air spark gap; the clock signal from the Rogowski belt after first breakdown is applied to the thyratron circuit and second capacitor discharges through it. This set of events leads to

Delay of the second discharge ignition may be changed in range of 50 - 300 microsec‐ onds. The following parameters are measured: discharge current and the signal from the pressure sensor. The Rogowski belt has the sensitivity 125 A/V, and its signal is record‐ ed with an oscilloscope. Capacity for the first discharge (C1) = 0.105 µF and it is charged to U1 = 15 kV (energy E1 = 12 J), capacity for the second discharge C2 = 0.105 µF and it is

A distance between electrodes can be changed in the range of 0.25 - 1 mm. The second discharge can be ignited at the moment (according to the delay tuning) when the reflected acoustic wave, created by the first electric discharge in liquid, returns to the center of the system (the time of

(a) (b)

The composition of ethanol and bioethanol reforming products is studied with gas chromatography, in case of bioglycerol reforming - mass spectrometry and infrared

**Figure 17.** Photograph of the cylinder from the outside: a) horizontal position, b) vertical position.

the second breakdown of the discharge gap and second discharge appearance.

may be realized in the system also (airflow ~ 4 cm3

distillate and ethanol (96%, no flow).

charged to U2 = 18 kV (energy E2 = 17 J).

its collapse ~ 180 ms).

spectrophotometry.

/s). Additional supply of gas

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/s), which is injected through a spray nozzle

Hydrogen Conversion in DC and Impulse Plasma-Liquid Systems

#### **3. Dynamic impulse plasma–liquid systems**

#### **3.1. Experimental set up**

The experimental setting is shown in Fig. 16. The main part of the system is cylinder with height H = 10 mm, and radius R = 135 mm. Its lateral surface made of stainless steel with a thickness of 5 cm. This cylinder is filled with liquid for experimental operations. The electrodes are placed perpendicular to the cylinder axis. They have the diameter of 10 mm, made of brass, and their ends are shaped hemispheres with a radius of curvature of 5 mm. The discharge (2) is ignited between the rounded ends of the electrodes. At a distance of 40 mm from the lateral surface of the cylinder is piezo-ceramic pressure sensor (3), which records acoustic vibrations in the fluid, caused by electric discharge under water. The distance between the sensor head and the system axis = L.

**Figure 16.** Schematic diagram of plasma-liquid system with a pulsed discharge, 1 - electrodes with brass tips, 2 – plas‐ ma, 3 – piezo-ceramic pressure sensor.

The cylindrical system could be located in a horizontal position (Fig. 17a) or vertical one (Fig. 17b). The full volume (0.5 l) of system is fluid-filled. The fluid in the system can be processed as in static mode (no flow), and dynamic one (with flow ~ 15 cm3 /s). Additional supply of gas may be realized in the system also (airflow ~ 4 cm3 /s), which is injected through a spray nozzle (source diameter 8 mm) located near the inner wall of the cylinder at a distance of 130 mm from the discharge gap (Fig. 16). The working fluids are: the tap water (with and without flow), distillate and ethanol (96%, no flow).

The main feature of electrical scheme for pulsed power feeding of discharge in a liquid is usage of two independent capacitors which are supplied two independent sources of power (1 kW). Pulsed discharge realized in two modes: single and double pulses. In the single pulse mode only one capacitor is discharged with a frequency of 0 - 100 Hz.

Double pulse mode is realized as follows: one capacitor discharges in the interelectrode gap through air spark gap; the clock signal from the Rogowski belt after first breakdown is applied to the thyratron circuit and second capacitor discharges through it. This set of events leads to the second breakdown of the discharge gap and second discharge appearance.

Delay of the second discharge ignition may be changed in range of 50 - 300 microsec‐ onds. The following parameters are measured: discharge current and the signal from the pressure sensor. The Rogowski belt has the sensitivity 125 A/V, and its signal is record‐ ed with an oscilloscope. Capacity for the first discharge (C1) = 0.105 µF and it is charged to U1 = 15 kV (energy E1 = 12 J), capacity for the second discharge C2 = 0.105 µF and it is charged to U2 = 18 kV (energy E2 = 17 J).

A distance between electrodes can be changed in the range of 0.25 - 1 mm. The second discharge can be ignited at the moment (according to the delay tuning) when the reflected acoustic wave, created by the first electric discharge in liquid, returns to the center of the system (the time of its collapse ~ 180 ms).

**Figure 17.** Photograph of the cylinder from the outside: a) horizontal position, b) vertical position.

The composition of ethanol and bioethanol reforming products is studied with gas chromatography, in case of bioglycerol reforming - mass spectrometry and infrared spectrophotometry.

#### **3.2. Results**

Oscillograms of current and acoustic signal for different distances between electrodes (0.5 and 1 mm) are presented in Fig. 18. These oscillograms show the presence of electrolysis phase before breakdown, while duration of electrolysis increases with interelectrode distance.

Fig. 19 shows the acoustic signal dependence from ballast resistor in the discharge electric circuit. The acoustic signal has two splashes: №1 - the first diverging acoustic wave, and №2 the second diverging acoustic wave. When the ballast resistor is increased, first and second acoustic signal splashes are decreased. This may be due to the fact: we increase the ballast resistor and set measures to the discharge current, as a result the injected into the discharge

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Also, there is a signal immediately behind the front of the first splash, which is founded in all cases at 110 microseconds interim from the beginning of the discharge current. The acoustic wave passes the way near 17 cm during this time. The pressure sensor is located at the distance of 2 cm from the lateral surface, so the acoustic signal passes the way near 12 cm to the sensor. Thus, there is a second stable signal after the first splash through time ~ 29 µs, which corre‐ sponds to the path ~ 4.4 cm, so the signal can be the convergent acoustic waves reflected from

**Figure 20.** Oscillograms of the discharge current (top oscillogram) and acoustic signal (lower oscillogram) at different

gap energy is diminished.

delays of the second discharge pulse.

the wall.

**Figure 18.** Oscillograms of the discharge current (top curve) and signal piezo-ceramic pressure sensor (lower curve): a) d = 0.5 mm, b) d = 1 mm. Tap water flow = 15 cm3/sec, without the input gas stream, C = 0.18 uF, U = 13.5 kV; ballast resistor in the discharge circle: Rb = 20 Ohm, the cylinder is in horizontal position.

**Figure 19.** Oscillograms of current and acoustic signal in the single pulse mode at the different discharge ballast resis‐ tor: Rb: a) - 0 Ohm, b) - 10 Ohm; c) - 20 Ohm, d) - 50 Ohm. Tap water flow 15 cm3/s, without the input gas stream, d = 0.5 mm, C = 0.015 µF, U = 19.5 kV, the cylinder is in horizontal position.

Fig. 19 shows the acoustic signal dependence from ballast resistor in the discharge electric circuit. The acoustic signal has two splashes: №1 - the first diverging acoustic wave, and №2 the second diverging acoustic wave. When the ballast resistor is increased, first and second acoustic signal splashes are decreased. This may be due to the fact: we increase the ballast resistor and set measures to the discharge current, as a result the injected into the discharge gap energy is diminished.

Also, there is a signal immediately behind the front of the first splash, which is founded in all cases at 110 microseconds interim from the beginning of the discharge current. The acoustic wave passes the way near 17 cm during this time. The pressure sensor is located at the distance of 2 cm from the lateral surface, so the acoustic signal passes the way near 12 cm to the sensor. Thus, there is a second stable signal after the first splash through time ~ 29 µs, which corre‐ sponds to the path ~ 4.4 cm, so the signal can be the convergent acoustic waves reflected from the wall.

**Figure 20.** Oscillograms of the discharge current (top oscillogram) and acoustic signal (lower oscillogram) at different delays of the second discharge pulse.

There is the third acoustic signal splash in the experiment, but it does not affect the second discharge pulse delay in relation to the first. In addition, there is no acoustic signal from to the second discharge pulse in the double pulse mode, although the single pulse signal is present in the single pulse mode (Fig. 20).

Wt), the interelectrode distance - 0.25 mm, working liquid - ethanol (96%), the input airflow is

**0 10 20 30 40**

**Figure 22.** Mass spectrum for double pulse mode. Ethanol is without flow, inlet gas stream - 4 cm3/s, d = 0.25 mm, C1

**0 10 20 30 40**

**Figure 23.** Mass spectrum for the single pulse mode. Ethanol without flow, inlet air flow - 4 cm3/s, d = 0.25 mm, C1 =

The mass spectrometric studies show that the main components of the output fuel mixture are: hydrogen, carbon dioxide, and molecular nitrogen. The values of these components in the mixture: H2 - 29%, CO - 17% for double pulse mode and H2 - 35%, CO - 7% for single pulse mode. That is, with the same molecular hydrogen output, the carbon dioxide yield is signifi‐

The typical mass spectrum (Fig. 24) of the ethanol reforming (ethanol aqueous solution ethanol with concentrations 3.5, 13 and 26 percents) in the "TORNADO-LE". The power is 640 Wt. It

is injected in the plasma for its generation, and inlet air flow is 55 cm3

**M/e**

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425

**M/e**

/s.

4 cm3 /s.

0.105 µF, U1 = 15 kV, the cylinder is in the vertical position, f = 15 Hz.

cantly increased in double pulses mode.

**I, a.u.**

= C2 = 0.105 µF, U1 = 15 kV, U2 = 18 kV, the cylinder is in the vertical position, f = 15 Hz.

**I, a.u.**

**Figure 21.** Oscillograms of the discharge current (top oscillogram) and the acoustic signal (lower oscillogram) in the single pulses mode. Working fluid - ethanol, d = 0.25 mm, C1 = 0.105 µF, U1 = 15 kV, the cylinder in the vertical position

Fig. 21 shows clearly that the duration and amplitude parameters for the first current pulse in the ethanol are virtually indistinguishable from the first current pulse in distilled water at any cylinder orientations. The ratio of the second acoustic signal amplitude to the first acoustic signal amplitude in the ethanol is noticeably less than in the tap water and distillate.

The results of oscillographic studies of the discharge current and acoustic signals in double pulses mode demonstrate that the first discharge in double pulses mode takes place in the narrow gas channel with a radius comparable to the size of the plasma channel, and the second discharge takes place in the wide channel with radius larger than the plasma channel.

Next, we present the results of ethanol reforming studies in the impulse plasma-liquid system with double pulses mode and their comparison with the results obtained for "TORNADO-LE".

The mass spectrometer studies of ethanol reforming in the impulse PLS of cylindrical geometry were carried out in the following modes: single pulse mode (C = 0.105 µF, U = 15 kV, f = 15 Hz, power 180 W) and double-pulse mode (C1 = C2 = 0.105 µF, U1 = 15 kV, U2 = 15 kV, f = 15 Hz, second pulse delay = 170 µs, this time is less on 10 µsec than collapse time, the power is 435 Wt), the interelectrode distance - 0.25 mm, working liquid - ethanol (96%), the input airflow is 4 cm3 /s.

**Figure 22.** Mass spectrum for double pulse mode. Ethanol is without flow, inlet gas stream - 4 cm3/s, d = 0.25 mm, C1 = C2 = 0.105 µF, U1 = 15 kV, U2 = 18 kV, the cylinder is in the vertical position, f = 15 Hz.

**Figure 23.** Mass spectrum for the single pulse mode. Ethanol without flow, inlet air flow - 4 cm3/s, d = 0.25 mm, C1 = 0.105 µF, U1 = 15 kV, the cylinder is in the vertical position, f = 15 Hz.

The mass spectrometric studies show that the main components of the output fuel mixture are: hydrogen, carbon dioxide, and molecular nitrogen. The values of these components in the mixture: H2 - 29%, CO - 17% for double pulse mode and H2 - 35%, CO - 7% for single pulse mode. That is, with the same molecular hydrogen output, the carbon dioxide yield is signifi‐ cantly increased in double pulses mode.

The typical mass spectrum (Fig. 24) of the ethanol reforming (ethanol aqueous solution ethanol with concentrations 3.5, 13 and 26 percents) in the "TORNADO-LE". The power is 640 Wt. It is injected in the plasma for its generation, and inlet air flow is 55 cm3 /s.

**Solvent Molecular mass Critical temperature, Tcrit Critical pressure, Pcrit Critical density, ρcrit**

CO2 44.01 303.9 7.38 (72.8) 0.468

H2O 18.015 647.096 22.064 (217.755) 0.322

ethanol 46.07 513.9 6.14 (60.6) 0.276

The presence of electrolysis phase preceding electrical breakdown of heterophase environment demonstrates that the discharge development in the liquid perform with microbubbles. This

The formation of convergent acoustic wave after reflection from the ideal solid cylindrical surface was investigated. It is shown that acoustic waves may be effectively focused during

The research of ethanol reforming in pulse plasma-liquid system has shown that transition from single pulse mode to double pulse mode is accompanied by reduction syn-gase ratio

When the working fluid is bioglycerol the K, Na, Ca lines are presented in emission spectra and there is a solid continuous spectrum, which indicates that microparticles are present in

On the base of our results in bioethanol and bioglycerol CO2-reforming by "TORNADO-LE"

**1.** This process has special features, connected with CO2 retarding role in the conversion

**2.** In this system there is the possibility of reforming of hydrocarbons with significant

**3.** All the diagnostic methods, used in the "TORNADO-LE" plasma-liquid system, indicate that there're no NOx compounds in the bioethanol and bioglycerol reforming products.

result confirms the theory of "bubble" breakdown proposed by Mark Kushner [12].

**Table 2.** Critical pаrаmeters of different solvents

these waves passage inside the system.

**5. General conclusions**

plasma-liquid system, we can say that:

viscosity (such as bioglycerol);

components combustion;

the discharge. Its temperature is T = 2800 ± 200 K.

**4. Discussion**

([H2]/[CO]).

**g/mol K MPa (bar) g/sm3**

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427

**Figure 24.** Mass spectrum of the output mixture in the ethanol reforming (ethanol - 26%) in "TORNADO-LE" PLS

The following Tab.1 shows the values ratio generating the volume unit of (H2 + CO) mixture per unit of electrical power, which is injected into the plasma under reforming process in the impulse PLS of cylindrical geometry with double pulses mode, and in the "TORNADO-LE":


**Table 1.** The volume unit of (H2 + CO) mixture per unit of electrical power in various PLS

The H2 and CO components yield increases with increasing of the ethanol aqueous solution concentration. This concentration has maximum value 26%, and H2 - 26%, CO - 14%. The results of these systems studies show, that the pressure, in region collapse of converging shock waves (with pulse energy > 10 J), exceeds critical (Tab. 2). So, the additional increase chemical activity due to supercritical processes inclusion can be achieved in this situation.


**Table 2.** Critical pаrаmeters of different solvents

#### **4. Discussion**

The presence of electrolysis phase preceding electrical breakdown of heterophase environment demonstrates that the discharge development in the liquid perform with microbubbles. This result confirms the theory of "bubble" breakdown proposed by Mark Kushner [12].

The formation of convergent acoustic wave after reflection from the ideal solid cylindrical surface was investigated. It is shown that acoustic waves may be effectively focused during these waves passage inside the system.

The research of ethanol reforming in pulse plasma-liquid system has shown that transition from single pulse mode to double pulse mode is accompanied by reduction syn-gase ratio ([H2]/[CO]).

When the working fluid is bioglycerol the K, Na, Ca lines are presented in emission spectra and there is a solid continuous spectrum, which indicates that microparticles are present in the discharge. Its temperature is T = 2800 ± 200 K.

#### **5. General conclusions**

On the base of our results in bioethanol and bioglycerol CO2-reforming by "TORNADO-LE" plasma-liquid system, we can say that:


The investigations of bioethanol and bioglycerol in pulse plasma-liquid system have shown:

[3] Nedybaliuk O.A., Chernyak V.Ya., Olszewskij S.V., Plasma-liquid system with re‐ verse vortex flow of "tornado" type (Tornado-LE) //Problems of atomic science and

Hydrogen Conversion in DC and Impulse Plasma-Liquid Systems

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[4] Xumei Tao, Meigui Bai, Xiang Li, e.a., CH4-CO2 reforming by plasma – challenges and opportunities // Progr. in Energy and Combustion Science 37, №2, pp. 113-124,

[5] V. Chernyak, Eu. Martysh, S. Olszewski, D. Levko. e.a., Ethanol Reforming in the Dy‐ namic Plasma - Liquid Systems, Biofuel Production-Recent Developments and Pros‐ pects, Marco Aurélio dos Santos Bernardes (Ed.), (2011). ISBN: 978-953-307-478-8,

[6] Lukes, P.; Sunka, P.; Hoffer, P.; Stelmashuk, V.; Benes, J.; e.a.,Book of Abstracts: NATO Science Advanced Research Workshop on Plasma for bio decontamination,

[7] Sheldon R. A. C. Catalytic conversions in water and supercritical carbon dioxide from the standpoint of sustainable development (in Russian) // Rus. Chem. J.,

[8] N.A.Popov, V.A. Shcherbakov, e.a. Thermonuclear fusion by exploding a spherical charge (gas-dynamical thermonuclear fusion problem) // Uspekhi, 10 (2008),

[9] Laux, C.O. Optical diagnostics of atmospheric pressure air plasma SPECAIR / C.O. Laux, T.G. Spence, C.H. Kruger, and R.N.Zare // Plasma Source Sci. Technol. – 2003. -

[11] D. Levko, A. Shchedrin, V. Chernyak e.a., Plasma kinetics in ethanol/water/air mix‐ ture in a 'tornado'-type electrical discharge // J. Phys. D: Appl. Phys. 44 (2011) 145206

[12] Kushner, M.J.; Babaeva, N.Yu. Plasma production in liquids: bubble and electronic

mechanism, Bulletin of the APS GES10, Paris, France, October 4–8, 2010.

technology, № 6. Series: Plasma Physics (16), p. 135-137. (2010).

medicine and food security, Jasná, Slovakia, March 15–18, 2011.

2011

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48(2004), 74-83.

Vol. 12, No. 2. - P. 125-138.

[10] Raizer Yu.P. Gas discharge physics (Springer, 1991)

1087-1094.

(13pp)


#### **Author details**

Valeriy Chernyak1\*, Oleg Nedybaliuk1 , Sergei Sidoruk1 , Vitalij Yukhymenko1 , Eugen Martysh1 , Olena Solomenko1 , Yulia Veremij1 , Dmitry Levko2,3, Alexandr Tsimbaliuk2 , Leonid Simonchik4 , Andrej Kirilov4 , Oleg Fedorovich5 , Anatolij Liptuga6 , Valentina Demchina7 and Semen Dragnev8

\*Address all correspondence to: chernyak\_v@ukr.net

1 Taras Shevchenko National University of Kyiv, Ukraine

2 Institute of Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine

3 Physics Department, Technion, 32000, Haifa, Israel

4 B.I. Stepanov Institute of Physics, National Academy of Sciences, Minsk, Belorus

5 Institute of Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine

6 V.E.Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, Kyiv, Ukraine

7 The Gas Institute, National Academy of Science of Ukraine, Kyiv, Ukraine

8 National University of Life and Environmental Sciences of Ukraine, Kyiv, Ukraine

#### **References**


**Chapter 14**

**Biofuels from Algae**

http://dx.doi.org/10.5772/53827

**1.1. Current sources of biofuels**

**1. Introduction**

production.

Robert Diltz and Pratap Pullammanappallil

Additional information is available at the end of the chapter

that can be used to replace standard petroleum based fuels.

properly cited.

The United States, as well as numerous other countries throughout the world, is seeing a rapid rise in the amount of power and fuel required to maintain the current and future life‐ styles of its citizens. With the rapid increase in global consumerism and travel seen over the recent decades due to improvements in technology and the increase in international interac‐ tions, the demand for fuel is rapidly growing, as can be seen in Figure 1. Due to the world‐ wide demand for fuel, which currently is primarily fossil-derived, supplies are being strained and costs are rapidly rising. In order to satiate this rapid increase in demand and stem the shrinking supply, new alternative sources of fuel must be brought to the market

Currently, there are several sources of alternative fuels that can be used to replace or supple‐ ment traditional petroleum based fuels. Some of these sources include alternative fossil-de‐ rived sources such as coal, natural gas, and hydrogen derived from hydrocracking, while other sources come from more renewable sources such as biomass. Biomass has several ad‐ vantages when it comes to fuels in that there are numerous sources such as terrestrially grown starch based or cellulosic material, waste derived material, or aquatic and marine based organisms, each of which has unique components and characteristics useful for fuel

Due to the structural variability of the various types of biomass available, a wide range of technologies can be used to convert the organic molecules into a useable form of fuel. As food substrates (such as carbon dioxide in autotrophic organisms or sugars in heterotrophic organisms) are metabolized, a range of cellular components are assembled to perform nu‐ merous duties to keep organisms alive and reproducing. Starches and celluloses are assem‐ bled from carbohydrates to provide rigid structural support in many woody biomasses as

> © 2013 Diltz and Pullammanappallil; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is

distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Diltz and Pullammanappallil; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

**Chapter 14**

### **Biofuels from Algae**

Robert Diltz and Pratap Pullammanappallil

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53827

#### **1. Introduction**

#### **1.1. Current sources of biofuels**

The United States, as well as numerous other countries throughout the world, is seeing a rapid rise in the amount of power and fuel required to maintain the current and future life‐ styles of its citizens. With the rapid increase in global consumerism and travel seen over the recent decades due to improvements in technology and the increase in international interac‐ tions, the demand for fuel is rapidly growing, as can be seen in Figure 1. Due to the world‐ wide demand for fuel, which currently is primarily fossil-derived, supplies are being strained and costs are rapidly rising. In order to satiate this rapid increase in demand and stem the shrinking supply, new alternative sources of fuel must be brought to the market that can be used to replace standard petroleum based fuels.

Currently, there are several sources of alternative fuels that can be used to replace or supple‐ ment traditional petroleum based fuels. Some of these sources include alternative fossil-de‐ rived sources such as coal, natural gas, and hydrogen derived from hydrocracking, while other sources come from more renewable sources such as biomass. Biomass has several ad‐ vantages when it comes to fuels in that there are numerous sources such as terrestrially grown starch based or cellulosic material, waste derived material, or aquatic and marine based organisms, each of which has unique components and characteristics useful for fuel production.

Due to the structural variability of the various types of biomass available, a wide range of technologies can be used to convert the organic molecules into a useable form of fuel. As food substrates (such as carbon dioxide in autotrophic organisms or sugars in heterotrophic organisms) are metabolized, a range of cellular components are assembled to perform nu‐ merous duties to keep organisms alive and reproducing. Starches and celluloses are assem‐ bled from carbohydrates to provide rigid structural support in many woody biomasses as

properly cited.

© 2013 Diltz and Pullammanappallil; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is © 2013 Diltz and Pullammanappallil; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

well as acting as a sugar storage method for quick conversion to a food source in times of famine. Proteins and amino acids are the building blocks of DNA structures and additional biomass. Lipids provide a highly energy dense storage system while also serving as a trans‐ port mechanism for several nutrients vital to metabolic activity. However, when broken down to the most basic levels, these organic compounds all contain energy which can be ex‐ tracted through several methods. Table 1 shows a breakdown of some common algal bio‐ mass cellular components.

**1.2. Aquatic biomass**

of discussion for the remainder of this article.

In order to produce the vast amounts of fuel needed by the United States, and the rest of the world, there will be a demand for massive quantities of biomass to be grown. This could be problematic when using terrestrial biomass, since in most cases, growing plants would re‐ quire a switch from using land for food sources to energy sources. An alternative source of biomass, however, is available in the form of aquatic and marine species of biomass such as kelps, algae, and other types of water borne plants or bacteria. Aquatic and marine biomass (excluding bacteria) are typically plant-like in that they are autotrophic organisms that con‐ tain photosynthetic pigmentation, can utilize inorganic carbon for biomass development, and express molecular oxygen as a byproduct. However, these organisms do not suffer from the inherent liability of requiring fertile soil to grow, minimizing competition with the food supply chain. Also, as microscopic organisms, they do not require abundance of land to de‐ velop root systems and large floral brush in order to absorb sunlight and nutrients, and therefore, a much more effective utilization of space. With rapid growth rates that can typi‐ cally double in concentration in less than a day, it is possible to have daily harvests, creating a steady and abundant supply of biomass for harvesting. As such, marine and aquatic bio‐ mass can be a useful alternative source of biomass that can be used to produce a wide range of biofuels for commercial use, while avoiding several of the more common pitfalls associat‐ ed with more traditional sources of terrestrial biomass, and thus, will be the biomass focus

Biofuels from Algae

433

http://dx.doi.org/10.5772/53827

Primarily, growth of algae for the production of oils and energy conversion has focused on microalgae, including species of diatoms and cyanobacteria (as opposed to macroalgae, such as seaweed), although some bacterial species (such as *Clostridium sp.)* have been demonstrat‐ ed for production of biologically derived hydrogen and methane [4]. To date, there have been numerous studies of algae and other water based biomass in order to identify strong candidates for biomass accumulation rates as well as lipid content for production of biodie‐ sel. Some strains are summarized for these characteristics in Table 2. There is also a wealth of microbial biomass resources available as a by-product of industrial activities such as sew‐ age treatment, brewing industries and food processing that could provide biomass or nu‐ trients for further microbial biomass growth [5, 6]. With this concept, it is feasible to use algae as a means for tertiary wastewater treatment in order to utilize trace nutrients such as phosphorous- and nitrogen-containing compounds, or can be used at industrial processes as a way to absorb carbon dioxide by entraining algal cultures to gaseous exhaust streams.

Growth of aquatic and marine biomass is not without challenges though. Maximum growth rates of the microorganisms typically occur under very specific conditions, and any variance on these conditions can cause substantial delays in biomass development. Also, open pond algal systems (which are common for algae production due to their ease of construction and inexpense) are susceptible to contamination from various airborne microorganisms that can decrease overall productivity. And of prime concern, is the ability to separate algae from water, which due to their very dilute nature, can be expensive and inefficient. Several meth‐ ods are used to do this, such as flocculation with chemicals (such as hydroxides or alum) or

**Figure 1.** Annual Consumption of Total Energy and Petroleum in the United States and the World [1]


**Table 1.** Variations in the chemical composition of selected algal species [2, 3]

Sources of biofuel currently being produced range in production rate from the laboratory scale through full scale implementation. Technologies to break down starches and cellulosic materials into sugars for subsequent conversion to bioalcohols has been extensively devel‐ oped and scaled to produce billions of gallons per year to add into petroleum derived gaso‐ line. Other structural components such as lipids have a high energy content to them and have characteristics that closely mimic petroleum diesel and kerosene, and thus, only re‐ quire simple chemical reaction (i.e., transesterification) for use as a biofuel, and have been developed up to a quasi-large scale of volumetric output that can be seen in some regional market places, as well as in home production for personal use.

#### **1.2. Aquatic biomass**

In order to produce the vast amounts of fuel needed by the United States, and the rest of the world, there will be a demand for massive quantities of biomass to be grown. This could be problematic when using terrestrial biomass, since in most cases, growing plants would re‐ quire a switch from using land for food sources to energy sources. An alternative source of biomass, however, is available in the form of aquatic and marine species of biomass such as kelps, algae, and other types of water borne plants or bacteria. Aquatic and marine biomass (excluding bacteria) are typically plant-like in that they are autotrophic organisms that con‐ tain photosynthetic pigmentation, can utilize inorganic carbon for biomass development, and express molecular oxygen as a byproduct. However, these organisms do not suffer from the inherent liability of requiring fertile soil to grow, minimizing competition with the food supply chain. Also, as microscopic organisms, they do not require abundance of land to de‐ velop root systems and large floral brush in order to absorb sunlight and nutrients, and therefore, a much more effective utilization of space. With rapid growth rates that can typi‐ cally double in concentration in less than a day, it is possible to have daily harvests, creating a steady and abundant supply of biomass for harvesting. As such, marine and aquatic bio‐ mass can be a useful alternative source of biomass that can be used to produce a wide range of biofuels for commercial use, while avoiding several of the more common pitfalls associat‐ ed with more traditional sources of terrestrial biomass, and thus, will be the biomass focus of discussion for the remainder of this article.

Primarily, growth of algae for the production of oils and energy conversion has focused on microalgae, including species of diatoms and cyanobacteria (as opposed to macroalgae, such as seaweed), although some bacterial species (such as *Clostridium sp.)* have been demonstrat‐ ed for production of biologically derived hydrogen and methane [4]. To date, there have been numerous studies of algae and other water based biomass in order to identify strong candidates for biomass accumulation rates as well as lipid content for production of biodie‐ sel. Some strains are summarized for these characteristics in Table 2. There is also a wealth of microbial biomass resources available as a by-product of industrial activities such as sew‐ age treatment, brewing industries and food processing that could provide biomass or nu‐ trients for further microbial biomass growth [5, 6]. With this concept, it is feasible to use algae as a means for tertiary wastewater treatment in order to utilize trace nutrients such as phosphorous- and nitrogen-containing compounds, or can be used at industrial processes as a way to absorb carbon dioxide by entraining algal cultures to gaseous exhaust streams.

Growth of aquatic and marine biomass is not without challenges though. Maximum growth rates of the microorganisms typically occur under very specific conditions, and any variance on these conditions can cause substantial delays in biomass development. Also, open pond algal systems (which are common for algae production due to their ease of construction and inexpense) are susceptible to contamination from various airborne microorganisms that can decrease overall productivity. And of prime concern, is the ability to separate algae from water, which due to their very dilute nature, can be expensive and inefficient. Several meth‐ ods are used to do this, such as flocculation with chemicals (such as hydroxides or alum) or electric fields, filtration, centrifugation, or thermal drying, but each of these methods is not without bulky equipment, expensive materials, or long processing times.

without problem in diesel engines; however, preheating of the fuel is required in order to reduce viscosity to pumpable levels. Biodiesel fuels, which are generally from the same source of lipids as straight vegetable oils or algal oils, are a much better suited fuel because they match several of the same characteristics as modern diesel fuel, and thus, require little

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Lipids are a general set of cellular components that are grouped together by the common trait that they are soluble in non-polar solvents. Throughout living organisms, there are sev‐ eral sources of lipids that play various roles in biochemical processes including energy stor‐ age and water insoluble nutrient transport across cell membranes that include neutral lipids, phospholipids, steroids, waxes, and carotenoids. Since lipids have a generally low oxygen and high carbon and hydrogen content, they are very energy dense molecules. This charac‐ teristic, along with their natural abundance and similarities with petroleum based fuels, make them ready targets for processing and use as a blend or replacement to traditional

Neutral lipids (commonly referred to as "fats"), which are widely regarded as one of the most common sources of lipids, and which has the highest potential for use as an alternative fuel, can be found in various forms throughout different organisms, and will be the primary topic of focus for this discussion. Most marine and aquatic biomass can store lipids within the cell that can range from a small fraction to upwards of 80% of the cellular weight. Due to this trait, research and production scale operations have been centered on utilizing aquatic biomass for lipid production and conversion to fuel with the remaining cellular components

to no engine modifications or fuel pretreatment modifications.

being recycled for mineral content or discarded.

**Figure 2.** Nile Red Fluorescence Image of *Nitzchia sp.*

**2.1. Sources of lipids**

fuels.

#### **2. Lipids and biodiesel**

The diesel engine, created by Rudolph Diesel in 1893 as an alternative to steam engines, has seen a marked rise in use over the past decades as newer engines coming to market have become such cleaner combustors. Since the engines are so efficient, they are ideal for use in heavy transport such as rail and ship, but as technology and advances in fuel make the en‐ gine emissions cleaner, more and more small engine vehicles are coming to market in light trucks and passenger cars in the US and Europe as well as the rest of the world.


**Table 2.** Productivity of Selected Algal Species

Diesel engines have the ability to run on various sources of fuel. Originally the engine was tested using pure peanut oil and vegetable oil, though today, the engine is commonly run on fossil fuel based diesel fuel, a type of kerosene. To reduce the amount of petroleum based diesel being used in today's market several alternative types of fuel have been introduced that are compatible with these engines. Among the alternatives, generally seen are the lipid based straight vegetable oils and the modified biodiesels. Straight vegetable oil will burn without problem in diesel engines; however, preheating of the fuel is required in order to reduce viscosity to pumpable levels. Biodiesel fuels, which are generally from the same source of lipids as straight vegetable oils or algal oils, are a much better suited fuel because they match several of the same characteristics as modern diesel fuel, and thus, require little to no engine modifications or fuel pretreatment modifications.

#### **2.1. Sources of lipids**

Lipids are a general set of cellular components that are grouped together by the common trait that they are soluble in non-polar solvents. Throughout living organisms, there are sev‐ eral sources of lipids that play various roles in biochemical processes including energy stor‐ age and water insoluble nutrient transport across cell membranes that include neutral lipids, phospholipids, steroids, waxes, and carotenoids. Since lipids have a generally low oxygen and high carbon and hydrogen content, they are very energy dense molecules. This charac‐ teristic, along with their natural abundance and similarities with petroleum based fuels, make them ready targets for processing and use as a blend or replacement to traditional fuels.

Neutral lipids (commonly referred to as "fats"), which are widely regarded as one of the most common sources of lipids, and which has the highest potential for use as an alternative fuel, can be found in various forms throughout different organisms, and will be the primary topic of focus for this discussion. Most marine and aquatic biomass can store lipids within the cell that can range from a small fraction to upwards of 80% of the cellular weight. Due to this trait, research and production scale operations have been centered on utilizing aquatic biomass for lipid production and conversion to fuel with the remaining cellular components being recycled for mineral content or discarded.

**Figure 2.** Nile Red Fluorescence Image of *Nitzchia sp.*

chain, and the carbon chain length, as each will have positive and negative attributes affect‐

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As the length of the molecule increases, the cetane number, and thus the heat of combustion, increases, this in turn decreases NOx emissions. However, as the length of the fatty acid chain increases, the resultant biodiesel has increased viscosity leading to a pre-heating re‐ quirement. Also, as fatty acids become more branched there is a benefit of the gel point (the temperature at which the fuel becomes gel-like and has complications flowing through fuel lines) decreasing. The negative to higher branching is that the cetane number will decrease due to a more difficult combustion. As saturation of the fatty acid chain increases, there is a decrease in NOx emissions and an improvement in fuel stability. As saturation increases,

there is an increase in melting point and viscosity, both undesirable traits in a fuel.

Since there are so many trade-offs in the production of biodiesel, it is very difficult, if not impossible, to pick one ideal source of fatty acid for conversion to fuel. The multitude of cli‐ mates across the globe will necessitate various traits in fuel such as the gel point, melting/ freezing point, and oxidative stability. This leads to the argument of localized production of specific biomass sources that can be tailored to produce the types of lipids most suited to fuel that specific region, which will keep transportation costs down, as well as provide for the local economy. In following this method, there will be ample biomass produced to meet the specific needs of each climate, reducing environmental stresses that can occur due to

Due to the various conditions that microorganisms grow and the constant flux of nu‐ trients that can persist in nature, there are numerous types of lipids found that can change in concentration as the local environments evolve through typical ebbs and flows of materials. In response to these changes, microorganisms will change their cellular struc‐ tures (i.e., lipid accumulation) by storing energy in various forms in order to utilize exist‐ ing nutrients and energy to prepare for leaner conditions that may occur. In practical terms, this concept can be leveraged in order to produce high concentrations of intracellu‐ lar lipids in marine and aquatic biomass in order to maximize the amount of lipids that can be harvested. Several studies have been conducted to determine what conditions af‐ fect the lipid composition and concentration of microorganisms. The more common tech‐ niques applied to increase the production of lipids from algae have through genetic manipulation [16], where genetic markers are manipulated that allow for increased lipid production to occur in the cell under normal conditions, by alteration of the cultivation conditions[17, 18], or by addition and manipulation of nutrients and chemicals added to the media [19]. By utilizing methods such as these, algal lipids can be increased by a sub‐ stantial amount without increasing the footprint of required reactor space, nor greatly in‐

ing fuel performance.

overproduction for large scale purposes.

**2.3. Enhancement of lipid production**

creasing the amount of time between harvests.

**Scheme 1.** Transesterification reaction schematic

Figure 2 shows an example of a marine diatom *Niztchia sp.* stained with Nile Red fluores‐ cence stain (red color shows chlorophyll and yellow shows lipid fluorescence).

Neutral lipids consist of a glycerol molecule (a three carbon alcohol) and one to three fatty acids (referred to as mono-, di-, or tri- acylglycerols depending on number of fatty acids present) with the fatty acids being various carbon chain lengths and having various levels of unsaturation (unsaturated, mono-unsaturated, poly-unsaturated, etc.). Fatty tissues in ani‐ mals serve as both an energy storage mechanism as well as a means of insulation against temperature extremes. Algae primarily store fats in the cell membrane to serve as an energy storage medium as well as a nutrient transport system to shuttle metabolites into and out of the cell. Several studies have been conducted to attempt to identify the distribution of fatty acids in algae and other aquatic biomass [13-15].

#### **2.2. Ideal lipid characteristics for biodiesel**

Biodiesel is produced primarily through the transesterification reaction of triglycerides and alcohol usually in the presence of a metal catalyst and can be visualized by the chemical re‐ action equation found in Scheme 1. where "R" groups are functional carbon chains varying in length and level of saturation and "M" is a metal, usually referring to sodium or potassi‐ um. The resultant glycerol that is produced is generally treated as a by-product and either sold for commodities use or burned to provide heating if necessary. This process is depend‐ ent on water content and pH, which dictates pre-processing demands in order to minimize the formation of soaps and maximize the production of wanted fatty acid ester compounds.

During this reaction the fatty acids tails are removed from the glycerol backbone leaving a glycerol molecule and one to three fatty acid esters (almost always either ethyl or methyl al‐ cohol yielding a methyl or ethyl ester). These fatty acid methyl esters (FAME) or ethyl esters (FAEE) will vary in characteristics as a fuel based on carbon chain length as well as degree of unsaturation and location of unsaturated bonds. Some of the characteristics of biodiesel that are affected by fatty acid chemistry are viscosity, cloud point, and freezing point, among other factors important to engine performance. In general, there are several tradeoffs that must be made with regards to saturation of fatty acids, branching of the fatty acid chain, and the carbon chain length, as each will have positive and negative attributes affect‐ ing fuel performance.

As the length of the molecule increases, the cetane number, and thus the heat of combustion, increases, this in turn decreases NOx emissions. However, as the length of the fatty acid chain increases, the resultant biodiesel has increased viscosity leading to a pre-heating re‐ quirement. Also, as fatty acids become more branched there is a benefit of the gel point (the temperature at which the fuel becomes gel-like and has complications flowing through fuel lines) decreasing. The negative to higher branching is that the cetane number will decrease due to a more difficult combustion. As saturation of the fatty acid chain increases, there is a decrease in NOx emissions and an improvement in fuel stability. As saturation increases, there is an increase in melting point and viscosity, both undesirable traits in a fuel.

Since there are so many trade-offs in the production of biodiesel, it is very difficult, if not impossible, to pick one ideal source of fatty acid for conversion to fuel. The multitude of cli‐ mates across the globe will necessitate various traits in fuel such as the gel point, melting/ freezing point, and oxidative stability. This leads to the argument of localized production of specific biomass sources that can be tailored to produce the types of lipids most suited to fuel that specific region, which will keep transportation costs down, as well as provide for the local economy. In following this method, there will be ample biomass produced to meet the specific needs of each climate, reducing environmental stresses that can occur due to overproduction for large scale purposes.

#### **2.3. Enhancement of lipid production**

Due to the various conditions that microorganisms grow and the constant flux of nu‐ trients that can persist in nature, there are numerous types of lipids found that can change in concentration as the local environments evolve through typical ebbs and flows of materials. In response to these changes, microorganisms will change their cellular struc‐ tures (i.e., lipid accumulation) by storing energy in various forms in order to utilize exist‐ ing nutrients and energy to prepare for leaner conditions that may occur. In practical terms, this concept can be leveraged in order to produce high concentrations of intracellu‐ lar lipids in marine and aquatic biomass in order to maximize the amount of lipids that can be harvested. Several studies have been conducted to determine what conditions af‐ fect the lipid composition and concentration of microorganisms. The more common tech‐ niques applied to increase the production of lipids from algae have through genetic manipulation [16], where genetic markers are manipulated that allow for increased lipid production to occur in the cell under normal conditions, by alteration of the cultivation conditions[17, 18], or by addition and manipulation of nutrients and chemicals added to the media [19]. By utilizing methods such as these, algal lipids can be increased by a sub‐ stantial amount without increasing the footprint of required reactor space, nor greatly in‐ creasing the amount of time between harvests.

#### **3. Synthetic fuels from biomass**

#### **3.1. Synthetic fuels**

Unlike biofuels, which transform biological molecules into petroleum substitutes, synthetic fuels take a raw biological material, and through chemical processing, create compounds identical to petroleum fuel. This has a very distinct advantage over common biofuels in that there are no compatibility issues between the traditional fuels nor is there a need for any en‐ gine or fuel line modifications required. Synthetic fuels are usually made by utilizing a com‐ plex biological molecule and through thermal processing, break down the material into simple chemical building blocks (i.e., methane, carbon monoxide, hydrogen, etc.) and re‐ form them into target chemicals. There are limitations with synthetic fuels production, espe‐ cially when pertaining to production from aquatic and marine biomass where the water content is naturally higher than 99% by weight in its natural state, since initial breaking down of the products is usually through thermal processing that require dry or near dry conditions. However, since algae and aquatic biomass has such diverse characteristics and high cellular energy density, there is benefit for using either algae where the lipids have been extracted or whole algal cells as feedstock for these thermal synthetic fuel processes and thus can be considered as an option for production of synthetic fuels.

herent advantages and drawbacks based on the complexity of the reactors, operating costs and product quality for use in the combustion of biomass. A more in-depth discussion of the design criteria and problems associated with using biomass as a fuel source for gasification

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Liquefaction is a process of converting biomass into a bio-oil in the presence of a solvent usually water, an alcohol, or acetone—and a catalyst [22]. Liquefaction operates at milder temperatures than gasification, but requires higher pressures. Liquefaction can be indirect, wherein biomass is converted into gas and thence into liquid, or direct, in which biomass is converted directly into liquid fuel [23]. Bio-oils produced in direct liquefaction processes usually produce heavy oils with high heating values and value-added chemicals as by-prod‐ ucts. Direct liquefaction also produces relatively little char compared to other thermochemi‐ cal processes that do not utilize solvents. In addition, liquefaction has the advantage that the method is not hindered by the water content of the biomass, giving credence to utilizing this method for water based biomass. The use of water as a solvent can significantly reduce op‐ erating costs, and recent studies with sub-and super-critical water have demonstrated in‐ creased process productivity by overcoming heat-transfer limitations [24, 25]. Operating parameters and feed quality significantly influence the overall quality of the oil produced by these processes. A recent review presented an exhaustive comparison of the operational var‐ iables that affect the liquefaction of biomass and concluded that a well-defined temperature range is the most influential parameter for optimizing bio-oil yield and biomass conversion [22]. Similarly, catalyst choice can alter the heating value of the final liquefaction product

Pyrolysis is a process in which organic matter is exposed to heat and pressure in the absence of oxygen. The primary components of this process are syngas molecules like those found in gasification, as well as bio-oils and charred solid residues [26]. Pyrolysis methods are de‐ fined by the rate of heating, which directly affects the residence time of the reaction [27]. In slow pyrolysis, for example, the material is exposed to reactor conditions for five minutes; in fast pyrolysis, residence time is reduced to one to two minutes and in flash pyrolysis to less than five seconds. The residence time of the pyrolysis reaction greatly influences the compo‐ sition of oils, gases and chars that are formed [28-30]. Several studies have been performed to identify the effect of operational variables— reactor conditions and variations in feed‐ stock material —on the quality of the pyrolysis oils, gases, and chars [27, 30]. The oils typi‐ cally produced during pyrolysis reactions are high in moisture content, and corrosive due to low pH. Pyrolysis of biomass is typically constrained by the high water content of the raw material, and current pyrolysis methods for biomass conversion have not reached the stage of commercial development. Ongoing research, however, aims at maximizing energy poten‐ tial from biomass and optimizing conversion methods to achieve commercialization at mar‐

reactors can be found in recent review articles [20, 21].

and reduce the quantity of solid residue [25].

**3.4. Liquefaction**

**3.5. Pyrolysis**

ketable levels [31, 32].

#### **3.2. Methods for synthetic fuel production**

There are three common methods for producing molecular precursors for synthetic fuels from biomass, and several variants of each method, dependent on the specific feedstock characteristic. These three methods are gasification, pyrolysis, and liquefaction. Pyrolysis and liquefaction will both produce of form of bio-oil that can be processed along with petro‐ leum oil stocks and made into useful fuel products, while gasification will produce gaseous products such as carbon monoxide, methane, and hydrogen (commonly called syngas or synthesis gas in this process), and can be further refined directly to produce specific fuel molecules.

#### **3.3. Gasification**

Gasification is a process in which carbonaceous materials are exposed to heat and a sub-stoi‐ chiometric concentration of air to produce partially oxidized gaseous products that still have a high heating value with relatively lower concentrations of carbon dioxide due to limited oxygen [20]. Syngas can be catalytically reformed into a liquid fuel through the Fischer– Tropsch process, which converts carbon monoxide and hydrogen into long-chain hydrocar‐ bons. By-products of the process include ash (formed from alkali-metal promoters present in the original reaction), char and tars that are created due to inefficiencies in mixing and heat distribution. This can be problematic when using water based biomass as the feedstock, since there will either be very high costs (in both energy and cost) to dry, or numerous un‐ wanted products formed through side reactions. Three main types of gasification reactor are commonly used in industry: fixed bed, fluidized bed and moving bed. Each process has in‐ herent advantages and drawbacks based on the complexity of the reactors, operating costs and product quality for use in the combustion of biomass. A more in-depth discussion of the design criteria and problems associated with using biomass as a fuel source for gasification reactors can be found in recent review articles [20, 21].

#### **3.4. Liquefaction**

Liquefaction is a process of converting biomass into a bio-oil in the presence of a solvent usually water, an alcohol, or acetone—and a catalyst [22]. Liquefaction operates at milder temperatures than gasification, but requires higher pressures. Liquefaction can be indirect, wherein biomass is converted into gas and thence into liquid, or direct, in which biomass is converted directly into liquid fuel [23]. Bio-oils produced in direct liquefaction processes usually produce heavy oils with high heating values and value-added chemicals as by-prod‐ ucts. Direct liquefaction also produces relatively little char compared to other thermochemi‐ cal processes that do not utilize solvents. In addition, liquefaction has the advantage that the method is not hindered by the water content of the biomass, giving credence to utilizing this method for water based biomass. The use of water as a solvent can significantly reduce op‐ erating costs, and recent studies with sub-and super-critical water have demonstrated in‐ creased process productivity by overcoming heat-transfer limitations [24, 25]. Operating parameters and feed quality significantly influence the overall quality of the oil produced by these processes. A recent review presented an exhaustive comparison of the operational var‐ iables that affect the liquefaction of biomass and concluded that a well-defined temperature range is the most influential parameter for optimizing bio-oil yield and biomass conversion [22]. Similarly, catalyst choice can alter the heating value of the final liquefaction product and reduce the quantity of solid residue [25].

#### **3.5. Pyrolysis**

Pyrolysis is a process in which organic matter is exposed to heat and pressure in the absence of oxygen. The primary components of this process are syngas molecules like those found in gasification, as well as bio-oils and charred solid residues [26]. Pyrolysis methods are de‐ fined by the rate of heating, which directly affects the residence time of the reaction [27]. In slow pyrolysis, for example, the material is exposed to reactor conditions for five minutes; in fast pyrolysis, residence time is reduced to one to two minutes and in flash pyrolysis to less than five seconds. The residence time of the pyrolysis reaction greatly influences the compo‐ sition of oils, gases and chars that are formed [28-30]. Several studies have been performed to identify the effect of operational variables— reactor conditions and variations in feed‐ stock material —on the quality of the pyrolysis oils, gases, and chars [27, 30]. The oils typi‐ cally produced during pyrolysis reactions are high in moisture content, and corrosive due to low pH. Pyrolysis of biomass is typically constrained by the high water content of the raw material, and current pyrolysis methods for biomass conversion have not reached the stage of commercial development. Ongoing research, however, aims at maximizing energy poten‐ tial from biomass and optimizing conversion methods to achieve commercialization at mar‐ ketable levels [31, 32].

#### **4. Ethanol**

Several species of cyanobacteria, including *Chlamydomonnas reinhardtii, Oscillatoria limosa, Microcystis PCC7806, Cyanothece PCC7822, Microcystis aeruginosa PCC7806 and Spirulina pla‐ tensis* produce ethanol via an intracellular photosynthetic process. After selecting strains for ethanol, salt and pH tolerance, ethanol production can be enhanced through genetic modifi‐ cation [33]. These strains are long-lived and can be grown in closed photobioreactors to pro‐ duce an ethanol containing algae slurry. This process for ethanol production from algae is currently being demonstrated by Algenol Biofuels [34-36]. The cyanobacteria are grown in flexible-film, polyethylene-based closed photobioreactors containing seawater or brackish water as medium. Industrial (or other waste) CO2 is sparged into the bags to enhance growth of the microorganisms. Nutrients (primarily nitrogen and phosphorus) are supplied to sustain growth. At maturity, the microorganisms produce ethanol. The ethanol in the liq‐ uid phase will maintain an equilibrium with the ethanol-water in the vapor phase. The etha‐ nol-water in vapor phase condenses along the walls of headspace which is collected by gravity for ethanol recovery. Algenol aims to produce 56,000 L of ethanol per hectare per year using 430 polyethylene bags established over a one hectare footprint each containing 4500 L of culture medium with a cyanobacteria concentration of 0.5 g/L. Unlike other algae derived biofuel processes, the algae are retained in the bags while the ethanol water conden‐ sate is removed for ethanol recovery. It is expected that the photobioreactors will be emptied once a year to replace the seawater, growth media and cyanobacteria.

content decreases below 7.5% (by volume). Energy required almost doubles when ethanol

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Another challenge would be the economical disposal of spent algal cultures. Sterilization and inactivation of large volumes of biomass can involve extremely energy intensive unit operations like heating, or expensive processes like ultra violet treatment or chlorination.

Biogasification (or anaerobic digestion) is a biochemical process that converts organic matter to biogas (a mixture of methane, 50-70%, and balance carbon dioxide) under anaerobic con‐ ditions. Biogas can be used as a replacement for natural gas or it can be converted to electric‐ ity. The process is mediated by a mixed, undefined culture of microorganisms at near ambient conditions. Several terrestrial biomass feedstocks (agricultural residues, urban or‐ ganic wastes, animal wastes and biofuel crops) have been anaerobically digested and com‐

Anaerobic digestion offers several advantages over other biofuel production processes like ethanol fermentation or thermochemical conversion. The microbial consortia in an anaerobic digester are able to naturally secrete hydrolytic enzymes for the solubilization of macromo‐ lecules like carbohydrates, proteins and fats. Therefore, unlike in ethanol fermentation proc‐ ess there is no need to incorporate a pretreatment step to solubilize the macromolecules prior to fermentation. In addition, since the process is mediated by a mixed undefined cul‐ ture, issues of maintaining inoculum (or culture) purity does not arise. Being a microbial process, there is no need to dewater the feedstock prior to processing unlike in thermochem‐ ical conversion where the feedstock is dried, to improve net energy yield. This is advanta‐ geous when it comes to processing aquatic biomass as these can be processed without dewatering. The anaerobic digestion process will also mineralize organic nitrogen and phos‐

The process primarily takes place in four steps. A mixed undefined culture of mciroorgan‐ isms mediates hydrolysis, fermentation, acetogenensis and methanogenesis of the organic substrates as shown in Figure 3. During hydrolysis, the complex organic compounds are broken down into simpler, soluble compounds like sugars, amino acids and fatty acids. These soluble compounds are fermented to a mixture of volatile organic acids (VOA). The higher chain VOAs like propionic, butyric, and valeric acids are then converted to acetic acid in the acetogenesis step. Acetic acid is converted to methane during methanogenesis. Hydrogen and carbon dioxide are also liberated during fermentation and acetogenesis. A different group of methanogens converts hydrogen and carbon dioxide to methane. This mixed microbial culture thrives in the pH range of 6-8. Digestion can be performed either at

Aquatic biomass – macrophytes [38], micro and macro algae, have all been tested as feed‐ stock for biogasification. Microalgae have proportions of proteins (6–52%), lipids (7–23%)

mercial scale digesters exist for the biogasification of such feedstocks.

phorous, and these nutrients can be recycled for algae growth [37].

mesophilic conditions (30 - 38ºC) or thermophilic conditions (49 - 57ºC).

content decreases from 12% down to 5% (by volume).

**5. Anaerobic digestion**

The ethanol concentration in the algal cultures is expected to range between 0.5 and 5 % (w/w) depending on the ethanol tolerance levels of the strain and that of the condensate be‐ tween 0.5 and 2% [36]. Since the maximum ethanol concentration is expected to be only 2 %, conventional distillation for ethanol recovery will not be energy efficient. A vapor compres‐ sion steam stripping (VCSS) process is being developed to concentrate the ethanol to 5-30 % (w/w) range. VCSS is a highly heat integrated process that offers the potential for energy ef‐ ficient separation even at low ethanol concentrations. This is then followed by a vapor com‐ pression distillation process to concentrate ethanol to an azeotropic 94% concentration. Life cycle energy requirements and greenhouse gas emissions for the process are dependent on the ethanol content of the condensate from the photobioreactors. Detailed analysis using process simulation software have shown that net life cycle energy consumption (excluding photosynthesis) is 0.55 down to 0.2 MJ/MJethanol and net life cycle greenhouse gas emissions is 29.8 down to 12.3 g CO2e/MJethanol for ethanol concentrations ranging from 0.5 to 5% by weight [36]. Compared to gasoline these values represent a 67% and 87% reduction in the carbon footprint on an energy equivalent basis [36].

One of the technological challenges for this approach appears to be developing genetically engineered cyanobacterial strains that can tolerate high concentrations of ethanol. The etha‐ nol concentration in the growth medium will affect the vapor phase ethanol content which in turn will affect the content of the condensate recovered from the photobioreactor. There is a dramatic increase in energy consumption in a conventional distillation process as ethanol content decreases below 7.5% (by volume). Energy required almost doubles when ethanol content decreases from 12% down to 5% (by volume).

Another challenge would be the economical disposal of spent algal cultures. Sterilization and inactivation of large volumes of biomass can involve extremely energy intensive unit operations like heating, or expensive processes like ultra violet treatment or chlorination.

#### **5. Anaerobic digestion**

Biogasification (or anaerobic digestion) is a biochemical process that converts organic matter to biogas (a mixture of methane, 50-70%, and balance carbon dioxide) under anaerobic con‐ ditions. Biogas can be used as a replacement for natural gas or it can be converted to electric‐ ity. The process is mediated by a mixed, undefined culture of microorganisms at near ambient conditions. Several terrestrial biomass feedstocks (agricultural residues, urban or‐ ganic wastes, animal wastes and biofuel crops) have been anaerobically digested and com‐ mercial scale digesters exist for the biogasification of such feedstocks.

Anaerobic digestion offers several advantages over other biofuel production processes like ethanol fermentation or thermochemical conversion. The microbial consortia in an anaerobic digester are able to naturally secrete hydrolytic enzymes for the solubilization of macromo‐ lecules like carbohydrates, proteins and fats. Therefore, unlike in ethanol fermentation proc‐ ess there is no need to incorporate a pretreatment step to solubilize the macromolecules prior to fermentation. In addition, since the process is mediated by a mixed undefined cul‐ ture, issues of maintaining inoculum (or culture) purity does not arise. Being a microbial process, there is no need to dewater the feedstock prior to processing unlike in thermochem‐ ical conversion where the feedstock is dried, to improve net energy yield. This is advanta‐ geous when it comes to processing aquatic biomass as these can be processed without dewatering. The anaerobic digestion process will also mineralize organic nitrogen and phos‐ phorous, and these nutrients can be recycled for algae growth [37].

The process primarily takes place in four steps. A mixed undefined culture of mciroorgan‐ isms mediates hydrolysis, fermentation, acetogenensis and methanogenesis of the organic substrates as shown in Figure 3. During hydrolysis, the complex organic compounds are broken down into simpler, soluble compounds like sugars, amino acids and fatty acids. These soluble compounds are fermented to a mixture of volatile organic acids (VOA). The higher chain VOAs like propionic, butyric, and valeric acids are then converted to acetic acid in the acetogenesis step. Acetic acid is converted to methane during methanogenesis. Hydrogen and carbon dioxide are also liberated during fermentation and acetogenesis. A different group of methanogens converts hydrogen and carbon dioxide to methane. This mixed microbial culture thrives in the pH range of 6-8. Digestion can be performed either at mesophilic conditions (30 - 38ºC) or thermophilic conditions (49 - 57ºC).

Aquatic biomass – macrophytes [38], micro and macro algae, have all been tested as feed‐ stock for biogasification. Microalgae have proportions of proteins (6–52%), lipids (7–23%) and carbohydrates (5–23%) that are strongly dependent on the species and environmental conditions [39-41]. Compared with terrestrial plants microalgae have a higher proportion of proteins, which is characterized by a low carbon to nitrogen (C/N) ratio. The average C/N for freshwater microalgae is around 10.2 while it is 36 for terrestrial plants [40]. Usually the digestion of terrestrial plants is limited by nitrogen availability; however for microalgae this situation does not arise. Besides carbon, nitrogen and phosphorus, which are major compo‐ nents in microalgae composition, oligo nutrients such as iron, cobalt, zinc are also found [42]. These characteristics of microalgae make it a good feedstock for anaerobic digestion.

type of microalgae, the methane potentials range from 5 to 78% of methane potential of cel‐

More recently when *Nannochloropsis oculata* was biogasified [48] in laboratory scale digesters at thermophilic temperature, the methane yield obtained was 0.20 L at STP/g VS. *N. oculata* was chosen because it can be grown easily in brackish or seawater, has a satisfactory growth rate and can tolerate a wide range of pH (7-10) and temperature (17 – 27º C). *N. oculata* is not rich in lipids but contains predominantly cellulose and other carbohydrates, which makes it a good feedstock for anaerobic digestion instead of biodiesel production. On a % (w/w dry matter) basis, the composition of *N. oculata* is: 7.8% carbohydrate, 35% protein and 18% lip‐ id. Rest of the components are amino acids, fatty acids, omega-3, unsaturated alcohols, as‐ corbic acid [49]. About 88% of the carbohydrate is polysaccharide. Of the polysaccharides, 68.2% is glucose, and the rest are fucose, galactose, mannose, rhamnose, ribose and xylose.

Based on *N. oculata* growth observed in the pilot raceways and the methane yield from di‐ gestion of this alga, an analysis was carried out to estimate energy production and land re‐ quirements. Currently the algae harvesting rate from the raceways are 9.64 g ash free dry

tent. An often cited study for algae growth has yielded a much higher productivity of 50 g

about 20% of the productivity potentially attainable. Optimization of growth conditions for *N. oculata* may improve its productivity. Using the methane yield value of 204 L/kg VS for anaerobic digestion of *N. oculata*, the annual energy output from a facility that grows the al‐

the digester(s) would be far less than the land area required for growing the algae. If the methane produced from this facility is converted to electricity, the electrical energy output

electrical energy is 30%. The household electrical energy and natural gas consumption in the

sification facility were to supply the entire electrical energy requirements for a household,

ply the natural gas needs, then an additional 2900 m2 (0.77 acres) would be needed. In other words ~2 acres of land could supply all the energy needs of a household in US. If the algae productivities were improved then land requirement could be further reduced. At 50 g

/d algae productivity, the land requirement would only be about 0.4 acres.

Despite useful methane production potential from biogasification and the ability to process dilute algal slurries in a digester, there are challenges to be overcome to commercialize this approach for producing bioenergy from microalgae. One bottleneck is that some feedstock characteristics can adversely affect anaerobic digestion. Unlike defined cultures used for production of biofuels like ethanol or butanol, the microbial consortia in an anaerobic di‐ gester is capable of secreting extracellular enzymes to hydrolyze and solubilize macromole‐ cules like cellulose, hemicellulose, proteins and fats. This characteristic has enabled several terrestrial biomass feedstocks like sugarbeets, sugarbeet tailings, napier grass, sorghum and aquatic biomass like water hyacinth and giant kelp to be successfully digested using practi‐

/d for *Platyomonas sp* [50]. The algae biomass yield obtained in this study was only

/d. Note that afdw (ash free dry weight) is the same as volatile solids con‐

/year assuming that the efficiency of converting thermal energy to

/year. The area occupied (or footprint) of

Biofuels from Algae

443

http://dx.doi.org/10.5772/53827

/year respectively. If the algae bioga‐

(1.26 acres). If in addition, the facility were to sup‐

lulose. Choice of microalgae has an impact on the methane yield.

gae and subsequently digests it would be 27 MJ/m2

US for the year 2010 was 11,496 kWH/year and 2070 m3

the land area required would be 5108 m2

weight (afdw)/m2

would be 2.25 kWHe/m2

afdw/m2

afdw/m2

**Figure 3.** Pathways for mineralization of organic matter to biogas in an anaerobic digestion process

Previous studies have shown that macro algae like *Ulva lactuca, Gracillaria vermiculophylla, Saccharina latissima* etc. can be anaerobically digested producing methane at yields ranging from 0.1-0.3 LCH4/g volatile solids (VS) [43]. Methane yields of microalgae like *Spirulina pla‐ tensis* (fresh water), and *Scenedesmus* spp. and *Chlorella* spp. (fresh water) ranged between 0.2 and 0.3 L CH4/g VS [44, 45] when these were codigested with other feedstocks like dairy manure and waste paper sludge, whereas other microalgae like *Tetraselmis sp* (marine), *Chlorella vulgaris* (fresh water), *Scendesmus obliquess* (fresh water) and *Phaeodactylum tricornu‐ tum* (fresh water) produced an average methane yield ranging from 0.17 to 0.28 L CH4/g VS [45-47] when digested as sole feedstock. Table 3 summarizes microalgae digestion studies reported in the literature. The Table also lists the methane yield of cellulose powder as a benchmark to compare the methane potentials of microalgae feedstocks. Depending on the type of microalgae, the methane potentials range from 5 to 78% of methane potential of cel‐ lulose. Choice of microalgae has an impact on the methane yield.

More recently when *Nannochloropsis oculata* was biogasified [48] in laboratory scale digesters at thermophilic temperature, the methane yield obtained was 0.20 L at STP/g VS. *N. oculata* was chosen because it can be grown easily in brackish or seawater, has a satisfactory growth rate and can tolerate a wide range of pH (7-10) and temperature (17 – 27º C). *N. oculata* is not rich in lipids but contains predominantly cellulose and other carbohydrates, which makes it a good feedstock for anaerobic digestion instead of biodiesel production. On a % (w/w dry matter) basis, the composition of *N. oculata* is: 7.8% carbohydrate, 35% protein and 18% lip‐ id. Rest of the components are amino acids, fatty acids, omega-3, unsaturated alcohols, as‐ corbic acid [49]. About 88% of the carbohydrate is polysaccharide. Of the polysaccharides, 68.2% is glucose, and the rest are fucose, galactose, mannose, rhamnose, ribose and xylose.

Based on *N. oculata* growth observed in the pilot raceways and the methane yield from di‐ gestion of this alga, an analysis was carried out to estimate energy production and land re‐ quirements. Currently the algae harvesting rate from the raceways are 9.64 g ash free dry weight (afdw)/m2 /d. Note that afdw (ash free dry weight) is the same as volatile solids con‐ tent. An often cited study for algae growth has yielded a much higher productivity of 50 g afdw/m2 /d for *Platyomonas sp* [50]. The algae biomass yield obtained in this study was only about 20% of the productivity potentially attainable. Optimization of growth conditions for *N. oculata* may improve its productivity. Using the methane yield value of 204 L/kg VS for anaerobic digestion of *N. oculata*, the annual energy output from a facility that grows the al‐ gae and subsequently digests it would be 27 MJ/m2 /year. The area occupied (or footprint) of the digester(s) would be far less than the land area required for growing the algae. If the methane produced from this facility is converted to electricity, the electrical energy output would be 2.25 kWHe/m2 /year assuming that the efficiency of converting thermal energy to electrical energy is 30%. The household electrical energy and natural gas consumption in the US for the year 2010 was 11,496 kWH/year and 2070 m3 /year respectively. If the algae bioga‐ sification facility were to supply the entire electrical energy requirements for a household, the land area required would be 5108 m2 (1.26 acres). If in addition, the facility were to sup‐ ply the natural gas needs, then an additional 2900 m2 (0.77 acres) would be needed. In other words ~2 acres of land could supply all the energy needs of a household in US. If the algae productivities were improved then land requirement could be further reduced. At 50 g afdw/m2 /d algae productivity, the land requirement would only be about 0.4 acres.

Despite useful methane production potential from biogasification and the ability to process dilute algal slurries in a digester, there are challenges to be overcome to commercialize this approach for producing bioenergy from microalgae. One bottleneck is that some feedstock characteristics can adversely affect anaerobic digestion. Unlike defined cultures used for production of biofuels like ethanol or butanol, the microbial consortia in an anaerobic di‐ gester is capable of secreting extracellular enzymes to hydrolyze and solubilize macromole‐ cules like cellulose, hemicellulose, proteins and fats. This characteristic has enabled several terrestrial biomass feedstocks like sugarbeets, sugarbeet tailings, napier grass, sorghum and aquatic biomass like water hyacinth and giant kelp to be successfully digested using practi‐ cal retention times. However, degradability of feedstocks containing high fraction of lignin (for example sugarcane bagasse, switchgrass, miscanthus and woody biomass like pine, eu‐ calyptus) is poor in an anaerobic digester. The refractoriness of these feedstocks has been at‐ tributed to low moisture, crystalline nature of the cellulose, and complex association of the component carbohydrates within lignin [51]. As seen from Table 3, the digestibility of micro‐ algae varies. Species with no cell wall or cell encapsulation composed of proteins like *Chlor‐ ella vulgaris* and *Phaeodactylum tricornutum*, has a higher yield of methane. *Dunaliella tertiolecta* has very low methane yield of 0.018 L/kg VS due to the presence of a cell wall con‐ sisting of cellulose fibers distributed within an organic matrix. So depending on the type of microalgae used it may be necessary to carry out some form of pretreatment of algae to im‐ prove methane yield and rate of methane production. The type of pretreatment may depend on algae type.

In order for biofuels sourced from aqueous and marine biomass to secure a market share in the world, research and development needs to further nature's ability to produce higher concentrations of biomass with targeted characteristics and reduced footprints, while better utilizing available nutrients. This will allow for an ample supply of biomass to be produced without competition with the human food chain, that can be used renewably produce fuel

Biofuels from Algae

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2 Department of Agricultural and Biological Engineering, University of Florida, Gainesville,

[1] U.S. Energy Information Administration. International Energy Statistics. http:// www.eia.gov/cfapps/ipdbproject/IEDIndex3.cfm?tid=5&pid=5&aid=2 (accessed Au‐

[2] Illman A, Scragg A, Shales S. Increase in Chlorella strains calorific values when grown in low nitrogen medium. *Enzyme and Microbial Technology* 2000; 27 631-635.

[3] Pan P, Hu C, Yang W, Li Y, Dong L, Zhu L, Tong D, Qing R, Fan Y. The direct pyrol‐ ysis and catalytic pyrolysis of *Nannochloropsis sp* residue for renewable bio-oils. *Biore‐*

[4] Collet C, Adler N, Schwitzguebel J, Peringer P. Hydrogen production by *Clostridium thermolacticum* during continuous fermentation of lactose. *International Journal of Hy‐*

[5] Iakovou E, Karagiannidis A, Vlachos D, Toka A, Malamakis A. Waste biomass-to-en‐ ergy supply chain management: A critical synthesis. *Waste Management* 2010; 30

[6] Virmond E, Schacker R, Albrecht W, Althoff C, Souza M, Moreira R, Jose H. Organic solid waste originating from the meat processing industry as an alternative energy

that can power the world's mobile fleet.

and Pratap Pullammanappallil2

\*Address all correspondence to: Robert.diltz@us.af.mil

1 Air Force Research Laboratory, Tyndall AFB, FL, USA

*source Technology* 2010; 101 4593-4599.

*drogen Energy* 2004; 29 1479-1485.

source. *Energy* 2010; 36 3897-3906.

**Author details**

Robert Diltz1

FL, USA

**References**

gust 6, 2012).

1860-1870.


**Table 3.** Summary of microalgae anaerobic digestion studies

#### **6. Conclusion**

Aqueous and marine biomass can be processed into a variety of sources of energy. Due to the extreme dilution in water, non-thermal processes such as anaerobic digestion, fermenta‐ tion to bioalcohols, and lipid extraction are logical and useful methods to utilize key compo‐ nents of microorganisms to produce biofuels for the replacement or supplementing of traditional fossil fuels. However, thermal methods such as gasification of wet biomass may play a role in producing specialty fuels such as jet fuel that require a specific ratio of higher hydrocarbons that would prove otherwise difficult to manufacture, even given the require‐ ment of intense drying.

In order for biofuels sourced from aqueous and marine biomass to secure a market share in the world, research and development needs to further nature's ability to produce higher concentrations of biomass with targeted characteristics and reduced footprints, while better utilizing available nutrients. This will allow for an ample supply of biomass to be produced without competition with the human food chain, that can be used renewably produce fuel that can power the world's mobile fleet.

#### **Author details**

Robert Diltz1 and Pratap Pullammanappallil2

\*Address all correspondence to: Robert.diltz@us.af.mil

1 Air Force Research Laboratory, Tyndall AFB, FL, USA

2 Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL, USA

#### **References**


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[21] Wang L, Weller C, Jones D, Hanna M. Contemporary issues in thermal gasification of biomass and its application to electricity and fuel production. *Biomass and Bioenergy*

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[22] Akhtar J, Amin N. A review on process conditions for optimum bio-oil yield in hy‐ droghermal liquefaction of biomass. *Renewable and Sustainable Energy Reviews* 2011;

[23] Rustamov V, Abdullayev K,Samedov E. Biomass conversion to liquid fuel by twostage thermochemical cycle. *Energy Conversion and Management* 1998; 39 (9) 869-875. [24] Xu C, Etcheverry T. Hydro-liquefaction of woody biomass in sub- and super-critical

[25] Sun P, Heng M, Sun S, Chen J. Direct liquefaction of paulownia in hot compressed

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[28] Hajaligol M, Waymack B, Kellogg D. Low temperature formation of aromatic hydro‐

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[30] Smets K, Adriaensens P, Reggers G, Schreurs S, Carleer R, Yperman J. Flash pyroly‐ sis of rapeseed cake: Influence of temperature on the yield and the characteristics of

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[34] Woods, P. Algenol Biofuels' Direct to Ethanol Technology AIChE, Nashville, TN

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Energy Laboratory report, July 1998.

*dustrial Microbiology* 1985; 26 235-246.


**Chapter 15**

**Biofuel: Sources, Extraction and Determination**

Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Bio‐ fuels include fuels derived from biomass conversion (Figure 1, JICA, Okinawa, Japan), as well as solid biomass, liquid fuels and various biogases. Although fossil fuels have their origin in ancient carbon fixation, they are not considered biofuels by the generally accept‐ ed definition because they contain carbon that has been "out" of the carbon cycle for a very long time. Biofuels are gaining increased public and scientific attention, driven by factors such as oil price hikes, the need for increased energy security, concern over green‐ house gas emissions from fossil fuels, and support from government subsidies. Biofuel is considered carbon neutral, as the biomass absorbs roughly the same amount of carbon dioxide during growth, as when burnt. The chemical composition of different kinds of

Biodiesel as one from important biofuel types is made from vegetable oils and animal fats. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from dieselpowered vehicles. Biodiesel is produced from oils or fats using transesterification and is the

Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sug‐ ar or starch crops such as corn or sugarcane. Cellulosic biomass, derived from non-food sources such as trees and grasses, is also being developed as a feedstock for ethanol produc‐ tion. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Current plant design does not provide for converting the lig‐

> © 2013 Shalaby; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

© 2013 Shalaby; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

distribution, and reproduction in any medium, provided the original work is properly cited.

nin portion of plant raw materials to fuel components by fermentation.

Additional information is available at the end of the chapter

Emad A. Shalaby

**1. Introduction**

http://dx.doi.org/10.5772/51943

biomass was shown in Table 1.

most common biofuel in Europe.

### **Biofuel: Sources, Extraction and Determination**

Emad A. Shalaby

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/51943

#### **1. Introduction**

Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Bio‐ fuels include fuels derived from biomass conversion (Figure 1, JICA, Okinawa, Japan), as well as solid biomass, liquid fuels and various biogases. Although fossil fuels have their origin in ancient carbon fixation, they are not considered biofuels by the generally accept‐ ed definition because they contain carbon that has been "out" of the carbon cycle for a very long time. Biofuels are gaining increased public and scientific attention, driven by factors such as oil price hikes, the need for increased energy security, concern over green‐ house gas emissions from fossil fuels, and support from government subsidies. Biofuel is considered carbon neutral, as the biomass absorbs roughly the same amount of carbon dioxide during growth, as when burnt. The chemical composition of different kinds of biomass was shown in Table 1.

Biodiesel as one from important biofuel types is made from vegetable oils and animal fats. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from dieselpowered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.

Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sug‐ ar or starch crops such as corn or sugarcane. Cellulosic biomass, derived from non-food sources such as trees and grasses, is also being developed as a feedstock for ethanol produc‐ tion. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Current plant design does not provide for converting the lig‐ nin portion of plant raw materials to fuel components by fermentation.

© 2013 Shalaby; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Shalaby; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

In 2010 worldwide biofuel production reached 105 billion liters (28 billion gallons US), up 17% from 2009, and biofuels provided 2.7% of the world's fuels for road transport, a contri‐ bution largely made up of ethanol and biodiesel. Global ethanol fuel production reached 86 billion liters (23 billion gallons US) in 2010, with the United States and Brazil as the world's top producers, accounting together for 90% of global production. The world's largest biodie‐ sel producer is the European Union, accounting for 53% of all biodiesel production in 2010. As of 2011, mandates for blending biofuels exist in 31 countries at the national level and in 29 states/provinces. According to the International Energy Agency, biofuels have the poten‐

Biofuel: Sources, Extraction and Determination

http://dx.doi.org/10.5772/51943

453

Here are 4 biofuel sources, with some of their application in developmental stages, some ac‐

*Algae come from* stagnant ponds in the natural world, and more recently in algae farms, which produce the plant for the specific purpose of creating biofuel. *Advantage of algae focude on the followings:* No CO2 back into the air, self-generating biomass, Algae can produce up to 300 times more oil per acre than conventional crops. Among other uses, algae have been used experimentally as a new form of green jet fuel designed for commercial travel. At the moment, the upfront costs of producing biofuel from algae on a mass scale are in process,

*It comes from* the fermentation of starches derived from agricultural products like corn, sugar cane, wheat, beets, and other existing food crops, or from inedible cellulose from the same. Produced from existing crops, can be used in an existing gasoline engine, making it a logical transition from petroleum. It used in Auto industry, heating buildings ("flueless fireplaces") At present, the transportation costs required to transport grains from harvesting to process‐ ing, and then out to vendors results in a very small net gain in the sustainability stakes.

*It comes from* existing food crops like rapeseed (aka Canola), sunflower, corn, and others, af‐ ter it has been used for other purposes, i.e food preparation ("waste vegetable oil", or WVO), or even in first use form ("straight vegetable oil", or SVO). Not susceptible to micro‐ bial degradation, high availability, re-used material. It is used in the creation of biodiesel fuel for automobiles, home heating, and experimentally as a pure fuel itself. At present, WVO or SVO is not recognized as a mainstream fuel for automobiles. Also, WVO and SVO

are susceptible to low temperatures, making them unusable in colder climates.

tial to meet more than a quarter of world demand for transportation fuels by 2050.

**2. Different sources of biofuel**

but are not yet commercially viable (Figure 2)

**2.2. Carbohydrate (sugars) rich biomaterial**

**2.3. Oils rich biomaterial**

tually implemented:

**2.1. Algae**

**Figure 1.** Cascade use of biomass


**Table 1.** Average properties of biomass

In 2010 worldwide biofuel production reached 105 billion liters (28 billion gallons US), up 17% from 2009, and biofuels provided 2.7% of the world's fuels for road transport, a contri‐ bution largely made up of ethanol and biodiesel. Global ethanol fuel production reached 86 billion liters (23 billion gallons US) in 2010, with the United States and Brazil as the world's top producers, accounting together for 90% of global production. The world's largest biodie‐ sel producer is the European Union, accounting for 53% of all biodiesel production in 2010. As of 2011, mandates for blending biofuels exist in 31 countries at the national level and in 29 states/provinces. According to the International Energy Agency, biofuels have the poten‐ tial to meet more than a quarter of world demand for transportation fuels by 2050.

#### **2. Different sources of biofuel**

Here are 4 biofuel sources, with some of their application in developmental stages, some ac‐ tually implemented:

#### **2.1. Algae**

*Algae come from* stagnant ponds in the natural world, and more recently in algae farms, which produce the plant for the specific purpose of creating biofuel. *Advantage of algae focude on the followings:* No CO2 back into the air, self-generating biomass, Algae can produce up to 300 times more oil per acre than conventional crops. Among other uses, algae have been used experimentally as a new form of green jet fuel designed for commercial travel. At the moment, the upfront costs of producing biofuel from algae on a mass scale are in process, but are not yet commercially viable (Figure 2)

#### **2.2. Carbohydrate (sugars) rich biomaterial**

*It comes from* the fermentation of starches derived from agricultural products like corn, sugar cane, wheat, beets, and other existing food crops, or from inedible cellulose from the same. Produced from existing crops, can be used in an existing gasoline engine, making it a logical transition from petroleum. It used in Auto industry, heating buildings ("flueless fireplaces") At present, the transportation costs required to transport grains from harvesting to process‐ ing, and then out to vendors results in a very small net gain in the sustainability stakes.

#### **2.3. Oils rich biomaterial**

*It comes from* existing food crops like rapeseed (aka Canola), sunflower, corn, and others, af‐ ter it has been used for other purposes, i.e food preparation ("waste vegetable oil", or WVO), or even in first use form ("straight vegetable oil", or SVO). Not susceptible to micro‐ bial degradation, high availability, re-used material. It is used in the creation of biodiesel fuel for automobiles, home heating, and experimentally as a pure fuel itself. At present, WVO or SVO is not recognized as a mainstream fuel for automobiles. Also, WVO and SVO are susceptible to low temperatures, making them unusable in colder climates.

**3. Comparison between different extraction methods of bio-diesel, bio-**

Biofuel: Sources, Extraction and Determination

http://dx.doi.org/10.5772/51943

455

Biodiesel is a clean-burning diesel fuel produced from vegetable oils, animal fats, or grease. Its chemical structure is that of fatty acid alkyl esters (FAAE). Biodiesel as a fuel gives much lower toxic air emissions than fossil diesel. In addition, it gives cleaner burning and has less sulfur content, and thus reducing emissions. Because of its origin from renewable resources, it is more likely that it competes with petroleum products in the future. To use biodiesel as a fuel, it should be mixedwith petroleum diesel fuel to create a biodiesel-blended fuel. Biodie‐ sel refers to the pure fuel before blending. Commercially, biodiesel is produced by transes‐ terification of triglycerides which are the main ingredients of biological origin oils in the presence of an alcohol (e.g. methanol, ethanol) and a catalyst (e.g. alkali, acid, enzyme) with glycerine as a major by-product [Ma and Hanna, 1999 ; Dube et al., 2007 ]. After the reaction, the glycerine is separated by settling or centrifuging and the layer obtained is purified prior to using it for its traditional applications (pharmaceutical, cosmetics and food industries) or for the recently developed applications (animal feed, carbon feedstock in fermentations, pol‐

However, one of the most serious obstacles to use biodiesel as an alternative fuel is the com‐ plicated and costly purification processes involved in its production. Therefore, biodiesel must be purified before being used as a fuel in order to fulfil the EN 14214 and ASTM D6751 standard specifications listed in Table 2; otherwise the methyl esters formed cannot be clas‐ sified as biodiesel. Removing glycerine from biodiesel is important since the glycerine con‐ tent is one of the most significant precursors for the biodiesel quality. Biodiesel content of glycerine can be in the form of free glycerine or bound glycerine in the form of glycerides. In this work we refer to the total glycerine, which is the sum of free glycerine and bound glyc‐ erine. Severe consequences may result due to the high content of free and total glycerine, such as buildup in fuel tanks, clogged fuel systems, injector fouling and valve deposits

For the synthesis of biodiesel, the following materials were used: oil sample (FFM Sdn Bhd), methanol (Merck 99%), and potassium hydroxide (KOH) as a catalyst (HMGM Chemicals >98%). Methanol and potassium hydroxide were pre-mixed to prepare potassium methox‐ ide, and then added to oil in the reactor with a mixing speed of 400 rpm for 2 h at 50 °C. The molar ratio of oil to methanol was 1:10. Finally, the mixture was left overnight to settle form‐ ing two layers, namely: biodiesel phase (upper layer) and the glycerin-rich phase (Figure 3).

ymers, surfactants, intermediates and lubricants) [Vicente et al., 2007].

**ethanol, biogas (bio-methane)**

**3.1. Biodiesel**

*3.1.1. Biodiesel extraction*

(Hayyan et al., 2010).

*3.1.2. Biodiesel extraction methods:*

*3.1.2.1. One step transesterification*

**Figure 2.** Dense algal growth in four pilot-scale tank bioreactors fed by treated wastewater from the Lawrence, Kan‐ sas (USA) wastewater treatment plant (photo by B. Sturm). Each fiberglass bioreactor has an operating volume of ten cubic meters of water, and is operated as an air-mixed, flow-through vessel. Nutrientrich wastewater inflows are pumped in through the clear plastic hose (blue clamp), and water outflow occurs through the white plastic pipe shown at the waterline. These bioreactors are intended to be operated year-round, as the temperature of the inflow‐ ing wastewater is consistently ca. 10 - 8°C.

#### **2.4. Agriculture wastes (organic and inorganic sources)**

It comes from agricultural waste which is concentrated into charcoal-like biomass by heat‐ ing it. Very little processing required, low-tech, naturally holds CO2 rather than releasing it into the air. Primarily, biochar has been used as a means to enrich soil by keeping CO2 in it, and not into the air. As fuel, the off-gasses have been used in home heating. There is contro‐ versy surrounding the amount of acreage it would take to make fuel production based on biochar viable on a meaningful scale. Furthermore, use of agriculture wastes which rich with inorganic elements (NPK----) as compost (fertilizer) in agriculture.

### **3. Comparison between different extraction methods of bio-diesel, bioethanol, biogas (bio-methane)**

#### **3.1. Biodiesel**

#### *3.1.1. Biodiesel extraction*

Biodiesel is a clean-burning diesel fuel produced from vegetable oils, animal fats, or grease. Its chemical structure is that of fatty acid alkyl esters (FAAE). Biodiesel as a fuel gives much lower toxic air emissions than fossil diesel. In addition, it gives cleaner burning and has less sulfur content, and thus reducing emissions. Because of its origin from renewable resources, it is more likely that it competes with petroleum products in the future. To use biodiesel as a fuel, it should be mixedwith petroleum diesel fuel to create a biodiesel-blended fuel. Biodie‐ sel refers to the pure fuel before blending. Commercially, biodiesel is produced by transes‐ terification of triglycerides which are the main ingredients of biological origin oils in the presence of an alcohol (e.g. methanol, ethanol) and a catalyst (e.g. alkali, acid, enzyme) with glycerine as a major by-product [Ma and Hanna, 1999 ; Dube et al., 2007 ]. After the reaction, the glycerine is separated by settling or centrifuging and the layer obtained is purified prior to using it for its traditional applications (pharmaceutical, cosmetics and food industries) or for the recently developed applications (animal feed, carbon feedstock in fermentations, pol‐ ymers, surfactants, intermediates and lubricants) [Vicente et al., 2007].

However, one of the most serious obstacles to use biodiesel as an alternative fuel is the com‐ plicated and costly purification processes involved in its production. Therefore, biodiesel must be purified before being used as a fuel in order to fulfil the EN 14214 and ASTM D6751 standard specifications listed in Table 2; otherwise the methyl esters formed cannot be clas‐ sified as biodiesel. Removing glycerine from biodiesel is important since the glycerine con‐ tent is one of the most significant precursors for the biodiesel quality. Biodiesel content of glycerine can be in the form of free glycerine or bound glycerine in the form of glycerides. In this work we refer to the total glycerine, which is the sum of free glycerine and bound glyc‐ erine. Severe consequences may result due to the high content of free and total glycerine, such as buildup in fuel tanks, clogged fuel systems, injector fouling and valve deposits (Hayyan et al., 2010).

#### *3.1.2. Biodiesel extraction methods:*

#### *3.1.2.1. One step transesterification*

For the synthesis of biodiesel, the following materials were used: oil sample (FFM Sdn Bhd), methanol (Merck 99%), and potassium hydroxide (KOH) as a catalyst (HMGM Chemicals >98%). Methanol and potassium hydroxide were pre-mixed to prepare potassium methox‐ ide, and then added to oil in the reactor with a mixing speed of 400 rpm for 2 h at 50 °C. The molar ratio of oil to methanol was 1:10. Finally, the mixture was left overnight to settle form‐ ing two layers, namely: biodiesel phase (upper layer) and the glycerin-rich phase (Figure 3).


stirred vigorously for 30 min at 30o

ly prepared PMS mixed at 60 rpm under reflux at 60o

sis (Shalaby and Nour, 2012; Shalaby, 2011).

step transterification as shown in Figure (4).

*3.1.2.3. Qualitative analysis of glycerol*

from these process.

**3.2. Bioethanol**

*3.2.1. Bioethanol extraction*

layer was transferred into water bath to remove excess methanol at 65o

hydroxyl group as in glycerol organic compound as the following:

and appearing after heating (direct) this positive control.

*3.1.2.4. Fourier transforms infrared spectroscopy (FTIR) analysis*

C. Then after, the mixture was carefully transferred

C for 30 min. afterwards; the mix‐

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C)

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to a separating funnel and allowed to stand for 4 h. the lower layer (glycerol, methanol and most of the catalysts) was drained out. The upper layer (methyl esters MEs, some methanol and traces of the catalyst) was transferred into another flask containing fresh‐

ture was carefully transferred to a separating funnel and allowed to stand there over night. The glycerol was removed by gravity settling, whereas the obtained crude esters

obtained crude methyl esters were then cleaned thoroughly by washing with warm (50o

deionized water, dried over anhydrous Na2SO4, weighted and applied for further analy‐

The Borax/phth test is special test for detection on the compound contain two neighboring

1 ml glycerol layer mix with 1 ml of Borax/phth (red color) if the red color disappear in cold

FTIR analysis was performed using instrument, Perkin Elmer, model spectrum one, for de‐ tection of transesterification efficiency of oil by determination of the active groups produced

The results obtained by Shalaby and Nour (2012) found that, two step transterification of oil led to 100 % disappearance of hydroxyl group but this was less than 100 % in case of one

Bioethanol is one of the most important renewable fuels due to the economic and environ‐ mental benefits of its use. The use of bioethanol as an alternative motor fuel has been steadi‐ ly increasing around the world for the number of reasons. 1) Fossil fuel resources are declining, but biomass has been recognized as a major reasons World renewable energy source. 2) Greenhouse gas emissions is one of the most important challenges in this century because of fossil fuel consumption, biofuels can be a good solution for this problem. 3) Price of petroleum in global market has raising trend. 4) Petroleum reserves are limited and it is monopoly of some oil-importing countries and rest of the world depends on them. 5) Also known petroleum reserves are estimated to be depleted in less than 50 years at the present rate of consumption. At present, in compare to fossil fuels, bioethanol is not produced eco‐

nomically, but according to scientific predictions, it will be economical about 2030.

**Table 2.** Biodiesel specifications according to EN 14214, and ASTM D6751 standards.

**Figure 3.** The biodiesel extraction process (steps).

#### *3.1.2.2. Second step transterification*

The production methodology followed in this study was according to Tomosevic and Si‐ ler-Marinkovic [2003] with some modification, where the alkali-catalyzed transesterifica‐ tion was applied. Basically, methanol was the alcohol of choice and KOH was used as the catalyst. Potassium methoxide solution (PMS) was prepared freshly by mixing a pre‐ determined amount of methanol (≈ 12 wt % of oil) with KOH (≈ 1.0 wt % of oil) in a container until all the catalyst dissolved. The PMS was then added to 200 g of oil and stirred vigorously for 30 min at 30o C. Then after, the mixture was carefully transferred to a separating funnel and allowed to stand for 4 h. the lower layer (glycerol, methanol and most of the catalysts) was drained out. The upper layer (methyl esters MEs, some methanol and traces of the catalyst) was transferred into another flask containing fresh‐ ly prepared PMS mixed at 60 rpm under reflux at 60o C for 30 min. afterwards; the mix‐ ture was carefully transferred to a separating funnel and allowed to stand there over night. The glycerol was removed by gravity settling, whereas the obtained crude esters layer was transferred into water bath to remove excess methanol at 65o C and 20 kPa. The obtained crude methyl esters were then cleaned thoroughly by washing with warm (50o C) deionized water, dried over anhydrous Na2SO4, weighted and applied for further analy‐ sis (Shalaby and Nour, 2012; Shalaby, 2011).

#### *3.1.2.3. Qualitative analysis of glycerol*

The Borax/phth test is special test for detection on the compound contain two neighboring hydroxyl group as in glycerol organic compound as the following:

1 ml glycerol layer mix with 1 ml of Borax/phth (red color) if the red color disappear in cold and appearing after heating (direct) this positive control.

#### *3.1.2.4. Fourier transforms infrared spectroscopy (FTIR) analysis*

FTIR analysis was performed using instrument, Perkin Elmer, model spectrum one, for de‐ tection of transesterification efficiency of oil by determination of the active groups produced from these process.

The results obtained by Shalaby and Nour (2012) found that, two step transterification of oil led to 100 % disappearance of hydroxyl group but this was less than 100 % in case of one step transterification as shown in Figure (4).

#### **3.2. Bioethanol**

#### *3.2.1. Bioethanol extraction*

Bioethanol is one of the most important renewable fuels due to the economic and environ‐ mental benefits of its use. The use of bioethanol as an alternative motor fuel has been steadi‐ ly increasing around the world for the number of reasons. 1) Fossil fuel resources are declining, but biomass has been recognized as a major reasons World renewable energy source. 2) Greenhouse gas emissions is one of the most important challenges in this century because of fossil fuel consumption, biofuels can be a good solution for this problem. 3) Price of petroleum in global market has raising trend. 4) Petroleum reserves are limited and it is monopoly of some oil-importing countries and rest of the world depends on them. 5) Also known petroleum reserves are estimated to be depleted in less than 50 years at the present rate of consumption. At present, in compare to fossil fuels, bioethanol is not produced eco‐ nomically, but according to scientific predictions, it will be economical about 2030.

Conventional methods for bioethanol production from lignocellulosic biomasses take three steps: *pretreatment* (commonly acid or enzyme hydrolyses), *fermentation, distillation*. Pretreat‐ ment is the chemical reaction that converts the complex polysaccharides to simple sugar. pretreatment of biomass is always necessary to remove and/or modify the surrounding ma‐ trix of lignin and hemicellulose prior to the enzymatic hydrolysis of the polysaccharides (cellulose and hemicellulose) in the biomass. Pretreatment refers to a process that converts lignocellulosic biomass from its native form. In general, pretreatment methods can be classi‐ fied into three categories, including physical, chemical, and biological pretreatment. In this step, biomass structure is broken to fermentable sugars. This project focused on chemically and biologically pretreatment. For example: this project shows the effect of sulfuric acid, hy‐ drochloric acid and acetic acid with different concentration by different conditions also shows the effect of cellulase enzyme by different techniques. Then fermentation step in which there are a series of chemical or enzymatic reactions that converted sugar into etha‐ nol. The fermentation reaction is caused by yeast or bacteria, which feed on the sugar such as *Saccharomyces cerevisae*. After that, distillation step in which the pure ethanol is separated from the mixture using distiller which boil the mixture by heater and evaporate the mixture

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to be condensate at the top of the apparatus to produce the ethanol from joined tube.

**Figure 5.** Ethanolic fermentation metabolism chart

**Figure 4.** The IR spectrum of oil after two step transterification (produced biodiesel) process

Biomass commonly gathers from agricultural, industrial and urban residues. The wastes used for bioethanol production are classified in three groups according to pretreatment process in sugary, starchy and lignocellulosic biomasses. Lignocellulosic biomass, including forestry residue, agricultural residue, yard waste, wood products, animal and human wastes, etc., is a renewable resource that stores energy from sunlight in its chemical bonds. Lignocellulosic biomass typically contains 50%-80% (dry basis) carbohydrates that are poly‐ mers of 5C and 6C sugar units. Lignocellulosic biomasses such as waste wood are the most promising feedstock for producing bioethanol.

Bioconversion of lignocellulosic biomass to ethanol is significantly hindered by the structur‐ al and chemical complexity of biomass, which makes these materials a challenge to be used as feedstock for cellulosic ethanol production. Cellulose and hemicellulose, when hydro‐ lyzed into their component sugars, can be converted into ethanol through well-established fermentation technologies. However, sugars necessary for fermentation are trapped inside the crosslinking structure of the lignocellulose.

Conventional methods for bioethanol production from lignocellulosic biomasses take three steps: *pretreatment* (commonly acid or enzyme hydrolyses), *fermentation, distillation*. Pretreat‐ ment is the chemical reaction that converts the complex polysaccharides to simple sugar. pretreatment of biomass is always necessary to remove and/or modify the surrounding ma‐ trix of lignin and hemicellulose prior to the enzymatic hydrolysis of the polysaccharides (cellulose and hemicellulose) in the biomass. Pretreatment refers to a process that converts lignocellulosic biomass from its native form. In general, pretreatment methods can be classi‐ fied into three categories, including physical, chemical, and biological pretreatment. In this step, biomass structure is broken to fermentable sugars. This project focused on chemically and biologically pretreatment. For example: this project shows the effect of sulfuric acid, hy‐ drochloric acid and acetic acid with different concentration by different conditions also shows the effect of cellulase enzyme by different techniques. Then fermentation step in which there are a series of chemical or enzymatic reactions that converted sugar into etha‐ nol. The fermentation reaction is caused by yeast or bacteria, which feed on the sugar such as *Saccharomyces cerevisae*. After that, distillation step in which the pure ethanol is separated from the mixture using distiller which boil the mixture by heater and evaporate the mixture to be condensate at the top of the apparatus to produce the ethanol from joined tube.

**Figure 5.** Ethanolic fermentation metabolism chart

The way to manufacture bioethanol is basically the same as that of liquor. Generally, saccha‐ rinity material such as sugar and starchy material such as rice and corn are saccharified (Figure 5-7), fermented and distilled till absolute ethanol whose alcoholicity is over 99.5%. It is technically possible to manufacture ethanol from cellulosic material such as rice straw or wood remains.

*3.2.2. How to produce bio-ethanol:*

**•** Materials

Sugarcane stems 5kg

Dry yeast, 15g

**•** Items

Brix meter, 5L flask, Dimroth condenser, Liebig condenser, Stick, Beaker

#### Cloth filter


**Figure 6.** Production of absolute ethanol from Saccharinity, Starch and Cellulosic materials

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**Figure 7.** The main steps of bioethanol production from Starchy and cellulosic materials (Masami YASUNAKA / JIR‐

CAS)


#### *3.2.3. Qualitative analysis for ethanol*

Iodoform test on cold is special test for ethanol as the following: I ml ethanol layer mix with iodide and sodium hydroxide after that, the presence of yellow crystal and iodoform odor produced, this meaning presence of ethanol.

**Figure 6.** Production of absolute ethanol from Saccharinity, Starch and Cellulosic materials

**Figure 7.** The main steps of bioethanol production from Starchy and cellulosic materials (Masami YASUNAKA / JIR‐ CAS)

*3.2.4.2. Dichromate oxidation method*

*3.2.4.3. Distillation-hydrometric method*

**3.3. Biogas (bio-methane) extraction**

ed (Anonymous. 1992; Collins et al., 1997).

environment at various stages of methane fermentation.

from industrial and agricultural surpluses.

Beverage sample solution (1~5 mL) was steam distillated to obtain alcoholic eluate (> 50 mL), and then oxidized with acidified dichromate. The excessive potassium dichromate was then titrated with ferric oxide. The ethanol content in beverage sample could be obtained by calculating the volume difference of potassium dichromate consumption between sample

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Alcoholic volatile compounds in beverage samples were separated by distillation, and the gravity of the distillate was measured by hydrometer. The ethanol content was then convert‐

Methane fermentation is a versatile biotechnology capable of converting almost all types of polymeric materials to methane and carbon dioxide under anaerobic conditions. This is ach‐ ieved as a result of the consecutive biochemical breakdown of polymers to methane and car‐ bon dioxide in an environment in which varieties of microorganisms which include fermentative microbes (acidogens); hydrogen-producing, acetate-forming microbes (aceto‐ gens); and methane-producing microbes (methanogens) harmoniously grow and produce reduced end-products (Fig. 10-11). Anaerobes play important roles in establishing a stable

Methane fermentation offers an effective means of pollution reduction, superior to that ach‐ ieved via conventional aerobic processes. Although practiced for decades, interest in anaero‐ bic fermentation has only recently focused on its use in the economic recovery of fuel gas

The biochemistry and microbiology of the anaerobic breakdown of polymeric materials to methane and the roles of the various microorganisms involved are discussed here. Recent progress in the molecular biology of methanogens is reviewed, new digesters are described

Methane fermentation is the consequence of a series of metabolic interactions among vari‐ ous groups of microorganisms. A description of microorganisms involved in methane fer‐ mentation, based on an analysis of bacteria isolated from sewage sludge digesters and from the rumen of some animals,. The first group of microorganisms secretes enzymes which hy‐ drolyze polymeric materials to monomers such as glucose and amino acids, which are sub‐ sequently converted to higher volatile fatty acids, H2 and acetic acid (Fig. 10). In the second stage, hydrogen-producing acetogenic bacteria convert the higher volatile fatty acids *e.g.,* propionic and butyric acids, produced, to H2, CO2*,* and acetic acid. Finally, the third group, methanogenic bacteria convert H2, CO2, and acetate, to CH4 and CO2 (Nagai et al., 1986).

and improvements in the operation of various types of bioreactors are also discussed.

solution and control solution (Anonymous. 1992; Collins et al., 1997).

**Figure 8.** The distillation process for ethanol production.

#### *3.2.4. Quantitative ethanol determination*

#### *3.2.4.1. Direct injected GC method*

Beverage sample solution (0.5 mL) was dispensed into an l-mL caped sample vial, and then 5 mL of 1% internal standard solution (equivalent to 50 mg) was added. After mixing, 0.1 µL of the sample solution was injected directly into a GC or GC/MS (Figure 9) with syringe (Anonymous. 1992; Collins et al., 1997).

#### *3.2.4.2. Dichromate oxidation method*

Beverage sample solution (1~5 mL) was steam distillated to obtain alcoholic eluate (> 50 mL), and then oxidized with acidified dichromate. The excessive potassium dichromate was then titrated with ferric oxide. The ethanol content in beverage sample could be obtained by calculating the volume difference of potassium dichromate consumption between sample solution and control solution (Anonymous. 1992; Collins et al., 1997).

#### *3.2.4.3. Distillation-hydrometric method*

Alcoholic volatile compounds in beverage samples were separated by distillation, and the gravity of the distillate was measured by hydrometer. The ethanol content was then convert‐ ed (Anonymous. 1992; Collins et al., 1997).

#### **3.3. Biogas (bio-methane) extraction**

Methane fermentation is a versatile biotechnology capable of converting almost all types of polymeric materials to methane and carbon dioxide under anaerobic conditions. This is ach‐ ieved as a result of the consecutive biochemical breakdown of polymers to methane and car‐ bon dioxide in an environment in which varieties of microorganisms which include fermentative microbes (acidogens); hydrogen-producing, acetate-forming microbes (aceto‐ gens); and methane-producing microbes (methanogens) harmoniously grow and produce reduced end-products (Fig. 10-11). Anaerobes play important roles in establishing a stable environment at various stages of methane fermentation.

Methane fermentation offers an effective means of pollution reduction, superior to that ach‐ ieved via conventional aerobic processes. Although practiced for decades, interest in anaero‐ bic fermentation has only recently focused on its use in the economic recovery of fuel gas from industrial and agricultural surpluses.

The biochemistry and microbiology of the anaerobic breakdown of polymeric materials to methane and the roles of the various microorganisms involved are discussed here. Recent progress in the molecular biology of methanogens is reviewed, new digesters are described and improvements in the operation of various types of bioreactors are also discussed.

Methane fermentation is the consequence of a series of metabolic interactions among vari‐ ous groups of microorganisms. A description of microorganisms involved in methane fer‐ mentation, based on an analysis of bacteria isolated from sewage sludge digesters and from the rumen of some animals,. The first group of microorganisms secretes enzymes which hy‐ drolyze polymeric materials to monomers such as glucose and amino acids, which are sub‐ sequently converted to higher volatile fatty acids, H2 and acetic acid (Fig. 10). In the second stage, hydrogen-producing acetogenic bacteria convert the higher volatile fatty acids *e.g.,* propionic and butyric acids, produced, to H2, CO2*,* and acetic acid. Finally, the third group, methanogenic bacteria convert H2, CO2, and acetate, to CH4 and CO2 (Nagai et al., 1986).

**3.4. Determination of methane concentration**

water from a port on your Winogradsky column.

ringe is 20 ml. Close the stopcock.

**3.6. Methane concentration calculation**

tion) detector.

ringe

**3.5. Calculations**

**4.1. Biodiesel**

*mended for similar reasons.*

Methane will be measured on the gas chromatogram (Figure 9)using a FID (flame ioniza‐

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*Note, unless you want smelly hands, it is recommended that you wear gloves. A lab coat is recom‐*

**•** Using a 20 ml syringe connected to a 2-way stopcock, collect a little more than 5 ml of

**•** With the syringe pointing up, remove any air (tapping the sides of the syringe) and expel any extra water so that the final liquid volume in the syringe is 5 ml. Do this over a sink. **•** Now, draw in 15 ml of air into the syringe so that the total air+water volume in the sy‐

**•** With the syringe pointing down, eject all the water from the syringe into the sink and close the stopcock. Try to get all the water out, but leave at least 10 ml of gas in the sy‐

To assist in plotting up results, measure the distance from the top of the sediment-water inter‐ face to each of the ports on the Winogradsky column, with distance to the ports in the sediment as positive and those in the water column negative. Also, measure the distance from the sedi‐

**•** From the standards, determine the concentration of methane in ppmv. Use the ideal gas

6 ppm 15 PV <sup>10</sup> <sup>1000</sup> n= = RT (0.08205)(293)

Most of the physical and chemical properties of the obtained methyl esters were determined by methods listed in JUS EN 14214:2004 standard [JUS EN 14214:2004] equivalent to EN 14214: 2003,

(1)

**•** Shake the syringe to equilibrate the methane between the air and water.

**•** We will now move to the GC lab in Starr 332 to measure methane.

**•** Repeat the above procedure for each of the ports on your Winogradsky column.

ment-water interface to the surface of the water and the bottom of the sediments.

law to determine the number of moles of methane in the 15 ml gas volume:

**4. Physico-chemical parameters of extracted biofuel**

**Figure 10.** The main steps for production of methane gas

**Figure 11.** The principles methods for biomethane production

#### **3.4. Determination of methane concentration**

Methane will be measured on the gas chromatogram (Figure 9)using a FID (flame ioniza‐ tion) detector.

*Note, unless you want smelly hands, it is recommended that you wear gloves. A lab coat is recom‐ mended for similar reasons.*


#### **3.5. Calculations**

To assist in plotting up results, measure the distance from the top of the sediment-water inter‐ face to each of the ports on the Winogradsky column, with distance to the ports in the sediment as positive and those in the water column negative. Also, measure the distance from the sedi‐ ment-water interface to the surface of the water and the bottom of the sediments.

#### **3.6. Methane concentration calculation**

**•** From the standards, determine the concentration of methane in ppmv. Use the ideal gas law to determine the number of moles of methane in the 15 ml gas volume:

$$\mathbf{n} = \frac{\mathbf{PV}}{\mathbf{RT}} = \frac{\frac{\mathbf{ppm}}{10^6}}{(0.08205)(293)} \frac{15}{(293)} \tag{1}$$

#### **4. Physico-chemical parameters of extracted biofuel**

#### **4.1. Biodiesel**

Most of the physical and chemical properties of the obtained methyl esters were determined by methods listed in JUS EN 14214:2004 standard [JUS EN 14214:2004] equivalent to EN 14214: 2003, which defines requirements and test methods for fatty acid methyl esters (FAME) to be used in diesel engine. It must be emphasized that the characterization of crude methyl esters (i.e. those obtained before the purification) was not performed as it is well known fact that such raw prod‐ ucts represent mixtures that were not in compliance with the strict restrictions for alternative die‐ sel fuels, as it contains glycerol, alcohol, catalyst, mono- and diglycerides besides fatty acid esters. Measurements of the density at 15 \_C by hydrometer method and of the kinematic viscosity at 40 \_C were carried out according to JUS EN ISO 3675:1988 and JUS ISO 3104:2003, respectively. The acid value (Av) was determined by titration in accordance to EN 14104:2003; the iodine value was obtained by Hannus method (EN 14111:2003) this property has been also previously used for the biodiesel characterization [Karaosmanog et al., 1996; Šiler-Marinkovic et al., 1998]. The method for the cetane index (CI) estimation based on the saponification (Sv) and iodine (Iv) values was previously described [Krisnangkura, 1986] as simpler and more convenient than experimental procedure for the cetane number determination utilizing a cetane engine (EN ISO 5165:1998). The Krisnangkura's equation [Krisnangkura, 1986] used for CI calculation was as follows: CI = 46.3 + 5458/Sv\_0.225 Iv. The cloud polint of MEs was determined according to ASTM D-2500 and Total sulfur content according to ASTM D-4294, Copper strip corrosion at 100 C according to ASTM D-130.The methyl ester composition was obtained by gas chromatograph equipped with DB-WAX 52 column (Supelco) and flame ionization detector. All the properties of frying oils as example were analyzed in two replicates and the final results given below were obtained as the average values (Table 3).

*4.1.3. Acid value*

*4.1.4. Iodine value*

*4.1.5. Saponification value*

The acid value measures the content of free acids in the sample, which have influence on fuel ag‐ ing. It is measured in terms of the quantity of KOH required to neutralize sample. The base cata‐ lyzed reaction is reported to be very sensitive to the content of free fatty acids, which should not exceed a certain limit recommended to avoid deactivation of catalyst, formation of soaps and emulsion [Sharma et al., 2008, Meher et al., 2004]. The feedstock acid values obtained in this study differed significantly ranging from 1.86 to 3.31 mg KOH/g oil. Thus, in the light of the previous discussion on the requirements for the feedstock acid values, it could be concluded that frying oil had the values above the recommended 2 mg KOH/g. However, these values did not turn out to be limiting for the efficiency of the applied two-stage process, as it will be discussed along to the obtained product yields and purity later on. Acid values of MEs were less than 0.5 mg KOH/ g specified as the maximum value according to JUS EN14214 (Table 4), Sharma et al. (2008) re‐ viewed the literature and found that acid value of the feedstock for alkaline transesterification has to be reduced to less than 2 mg KOH/g (i.e. 1%), while only few examples of transesterifica‐ tion with feedstock acid value of up to 4.0 mg KOH/g (i.e. 2%) were found. They also reported that when waste cooking oil is used as feedstock, the limit of free fatty acids is a bit relaxed and the value a little beyond 1% (i.e. 2 mg KOH/g) did not have any effect on the methyl ester conver‐ sion. Acid values of MEs produced from frying oil was 1.16 mgKOH/g when compared with 0.5 mg KOH/g specified as the maximum value according to JUS EN14214 [JUS EN 14214:2004].

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The iodine value of the feedstocks used in this study, which is a measure of unsaturation degree, was in the range of 70-78 mg I2/100 g. According to JUS EN 14214 [JUS EN 14214:2004], MEs used as diesel fuel must have an iodine value less than 120 g I2 per 100 g of sample. Methyl esters obtained in this study had iodine value in the range 72-80g I2/100 g and this finding is in accordance to the fatty acid composition, i.e. the calculated total unsa‐ turation degree of MEs (see Table 4). Iodine value depends on the feedstock origin and greatly influences fuel oxidation tendency. Consequently, in order to avoid oxidation.

The saponification value represents milligrams of potassium hydroxide required to saponify one gram of fat or oil. The obtained results indicated that in general, esters had higher sapo‐ nification values than the corresponding oils. Saponification values of the feedstocks and products analyzed here, ranged from 199 to 207 mg KOH/g oil. However, knowing that a triglyceride has 3 fatty acid chains associated and each triglyceride will give 3 methyl esters, stoichiometrically it may be expected that the same amount of fatty acid carbon chain in neat feedstock oil and the biodiesel will react with the same amount of KOH giving the soaps, i.e. their saponification values will be the same. But, could this assumption be also applied on the waste frying oils knowing that their properties differ significantly from the neat oils as a consequence of cyclization, polymerization and degradation of fatty acids.

#### *4.1.1. Density at 15 ⁰C*

It is known that biodiesel density mainly depends on its methyl esters content and the re‐ mained quantity of methanol (up to 0.2% m/m according to JUS EN 14214 [JUS EN 14214:2004]); hence this property is influenced primarly by the choice of vegetable oil [Mit‐ telbach, 1996], and in some extent by the applied purification steps. the mean density value of produced biodiesel was 0.90 g/cm3, while this value was more than Egyptian diesel (0.82-0.87g/cm3). but met the density value specified by JUS EN 14214 [JUS EN 14214:2004] to be in the range 0.860–0.900 g/cm3 at 15 ⁰C. This property is important mainly in airless combustion systems because it influences the efficiency of atomization of the fuel [Felizardo et al., 2006].

#### *4.1.2. Kinematic viscosity at 40 ⁰C*

Even more than density, kinematic viscosity at 40 ⁰C is an important property regarding fuel atomization and distribution. With regard to the kinematic viscosities that were in the range from 32.20 to 48.47 mm2/s, the feedstocks differed among themselves significantly. The vis‐ cosities of MEs were much lower than their respective oils (about 10 times) and they met the required values that must be between 3.5 and 5.0 mm2/s [JUS EN 14214:2004]. Comparing our MEs, the increase of the viscosities was observed more than Egyptian diesel, EN14214 and D-6751 (14.3, 7, 5 and 6 respectively) as shown in Table (3). However, the kinematic vis‐ cosity at 100 ⁰C of MEs produced from frying oil was met the viscosity range of Egyptian diesel, EN14214 and D-6751 (4.3, 7, 5 and 6 respectively). Predojevic (2008).

#### *4.1.3. Acid value*

The acid value measures the content of free acids in the sample, which have influence on fuel ag‐ ing. It is measured in terms of the quantity of KOH required to neutralize sample. The base cata‐ lyzed reaction is reported to be very sensitive to the content of free fatty acids, which should not exceed a certain limit recommended to avoid deactivation of catalyst, formation of soaps and emulsion [Sharma et al., 2008, Meher et al., 2004]. The feedstock acid values obtained in this study differed significantly ranging from 1.86 to 3.31 mg KOH/g oil. Thus, in the light of the previous discussion on the requirements for the feedstock acid values, it could be concluded that frying oil had the values above the recommended 2 mg KOH/g. However, these values did not turn out to be limiting for the efficiency of the applied two-stage process, as it will be discussed along to the obtained product yields and purity later on. Acid values of MEs were less than 0.5 mg KOH/ g specified as the maximum value according to JUS EN14214 (Table 4), Sharma et al. (2008) re‐ viewed the literature and found that acid value of the feedstock for alkaline transesterification has to be reduced to less than 2 mg KOH/g (i.e. 1%), while only few examples of transesterifica‐ tion with feedstock acid value of up to 4.0 mg KOH/g (i.e. 2%) were found. They also reported that when waste cooking oil is used as feedstock, the limit of free fatty acids is a bit relaxed and the value a little beyond 1% (i.e. 2 mg KOH/g) did not have any effect on the methyl ester conver‐ sion. Acid values of MEs produced from frying oil was 1.16 mgKOH/g when compared with 0.5 mg KOH/g specified as the maximum value according to JUS EN14214 [JUS EN 14214:2004].

#### *4.1.4. Iodine value*

The iodine value of the feedstocks used in this study, which is a measure of unsaturation degree, was in the range of 70-78 mg I2/100 g. According to JUS EN 14214 [JUS EN 14214:2004], MEs used as diesel fuel must have an iodine value less than 120 g I2 per 100 g of sample. Methyl esters obtained in this study had iodine value in the range 72-80g I2/100 g and this finding is in accordance to the fatty acid composition, i.e. the calculated total unsa‐ turation degree of MEs (see Table 4). Iodine value depends on the feedstock origin and greatly influences fuel oxidation tendency. Consequently, in order to avoid oxidation.

#### *4.1.5. Saponification value*

The saponification value represents milligrams of potassium hydroxide required to saponify one gram of fat or oil. The obtained results indicated that in general, esters had higher sapo‐ nification values than the corresponding oils. Saponification values of the feedstocks and products analyzed here, ranged from 199 to 207 mg KOH/g oil. However, knowing that a triglyceride has 3 fatty acid chains associated and each triglyceride will give 3 methyl esters, stoichiometrically it may be expected that the same amount of fatty acid carbon chain in neat feedstock oil and the biodiesel will react with the same amount of KOH giving the soaps, i.e. their saponification values will be the same. But, could this assumption be also applied on the waste frying oils knowing that their properties differ significantly from the neat oils as a consequence of cyclization, polymerization and degradation of fatty acids.

#### *4.1.6. Cetane index*

Krisnagkura [1986] proposed the equation for the estimation of cetane index (CI) based on the saponification and iodine values, recommending not to be used for oils, only for methyl esters. Namely, it has been previously documented that despite the fact that triglycerides and fatty acid methyl esters have similar saponification and iodine values, like it was ob‐ tained in this study too, cetane indexes of oils are generally much lower than those of meth‐ yl ester derivates. Thus, discussion on CI of frying oil will not be made. In this work, the CI value was 38 and this value less than the CI of Egyptian diesel, EN 14214 and D-6751 (55, 51 and 47 respectively). Šiler-Marinkovic´ and Tomaševic [1998] also used CI for the characteri‐ zation of methyl esters produced from crude frying oils, and the estimated values were from 49.7 to 50.9. As an alternative to cetane number, cetane index is also an indicator of ignition quality of the fuel and is related to the time that passes between injection of the fuel into the cylinder and onset of ignition [Knothe, 2005].

*4.1.7. Fatty acid composition*

(C 18:2) and stearic (C 18:0) acids.

produced biodiesel

**4.2. Bioethanol**

*4.2.1. Property of ethanol*

Melting point: -114.15

Molecular formula: C2H5OH

Molecular weight: 46.07

Toxicity: Get intoxicated

Specific gravity: 0.789

Boiling point: 78.3

As can be observed from Table 5, regardless of the fatty acid profiles were observed in the biodiesel produced from frying oil, consisting mainly of methyl esters of oleic (C 18:1), pal‐ mitic (C 16:0), and stearic (C 18:0) acids (30.60, 3.0 and 66.40 % respectively) and 2.8 % un‐ known fatty acid. these results are in agreement with the results obtained by Predojvic (2008) who reported that, fatty acid profiles were observed in the biodiesels produced from sun flower oil consisting mainly of methyl esters of oleic (C 18:1), palmitic (C 16:0), linoleic

**Acid value** mg KOH/g 5.1 0.48

**Iodine value** mg I2/g 62.0 60.0

**Saponification value** mg KOH/g 199.5 207.0

**Table 4.** Some chemical properties of waste cooking oil (WCO) used as feedstock for methyl esters preparation and

**Fatty acid ester Carbon number chain Wt% Molecular formula**

**Palmetic** 16 3.00 C16H32O2

**Stearic** 18 66.40 C18H36O2

**Oleic** 18 30.60 C18H34O2

**Table 5.** Composition of biodiesel obtained by transesterification of WCO using GC

**Parameters Feedstock Produced biodiesel**

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469


**Table 3.** Physicochemical properties for produced biodiesel compared to the Egyptian standards of petro-diesel fuel and two international biodiesel standards

#### *4.1.7. Fatty acid composition*

As can be observed from Table 5, regardless of the fatty acid profiles were observed in the biodiesel produced from frying oil, consisting mainly of methyl esters of oleic (C 18:1), pal‐ mitic (C 16:0), and stearic (C 18:0) acids (30.60, 3.0 and 66.40 % respectively) and 2.8 % un‐ known fatty acid. these results are in agreement with the results obtained by Predojvic (2008) who reported that, fatty acid profiles were observed in the biodiesels produced from sun flower oil consisting mainly of methyl esters of oleic (C 18:1), palmitic (C 16:0), linoleic (C 18:2) and stearic (C 18:0) acids.


**Table 4.** Some chemical properties of waste cooking oil (WCO) used as feedstock for methyl esters preparation and produced biodiesel


**Table 5.** Composition of biodiesel obtained by transesterification of WCO using GC

#### **4.2. Bioethanol**

*4.2.1. Property of ethanol*

Melting point: -114.15

Boiling point: 78.3

Molecular formula: C2H5OH

Molecular weight: 46.07

Specific gravity: 0.789

Toxicity: Get intoxicated

#### **4.3. Biomethane**


#### *4.3.1.2. Solid phase*


*4.3.2. Miscellaneous*

**5. Biofuel blending**

2003).

**•** Autoignition temperature : 595 °C

**•** Solubility in water (1.013 bar and 2 °C (35.6 °F)) : 0.054 vol/vol

your supplier that the fuel meets all ASTM specifications.

jobbers or a distribution company for sale to customers.

It is important that when you are purchasing fuel you make sure it is high quality by meet‐ ing all ASTM specifications. Fuel that is off specification on just one of the ASTM standards can not only cause serious engine problems, but it can void engine warranties if it is deter‐ mined that the fuel caused damage. This can cause unnecessary costly repairs for vehicles/ equipment. To review specifications for diesel fuel, biodiesel and biodiesel blends, see the specifications in the Appendix. In an effort ensure that producers and marketers operate in a manner consistent with proper specifications, the National Biodiesel Accreditation Commis‐ sion created the BQ-9000 program in 2005. This voluntary program establishes quality sys‐ tems for producers and marketers of biodiesel in the areas of storage, sampling, testing, blending, shipping, distribution and fuel management practices. If purchasing B100 or a bio‐ diesel blend, ask if the biodiesel is from a BQ-9000 biodiesel producer/marketer. If you are unable to get fuel from a BQ-9000 producer/marketer, the next best thing is to verify with

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In most cases the blending process takes place right at the terminal rack by a process called in-line blending. This is the preferred method because it ensures complete blending. In-line blending occurs when warm biodiesel is added to a stream of diesel fuel as it travels through a pipe or hose in such a way that the biodiesel and diesel fuel become thoroughly mixed by the turbulent movement. This product is sold directly to customers, petroleum

The blend level (percentage of biodiesel in the biodieseldiesel mixture) determines many im‐ portant characteristics of the blended fuel. A higher‐than‐specified level of biodiesel may ex‐ ceed the engine manufacturer's recommended limitation, compromising the engine performance. A lower blend level of biodiesel may reduce the expected benefits, such asfuel lubricity and tail pipe emission. In addition, cloud point and pour point of biodiesel are usu‐ ally higher than that of diesel fuel, and a higher blend level makes the fuel unsuitable or dif‐ ficult to use in cold weather conditions. Engine injection timing can be adjusted based on the blend level in order to improve the engine emission and performance (Tat and Van Gerpen,

It has been reported that the actual biodiesel content of blended biodiesel fuel sold at gas stations can be significantly different from the nominal blend level. A 2% nominal blend has been found to actually contain anywhere from 0% to 8% biodiesel (Ritz and Croudace, 2005). There are several reasons why the actual blend level may differ from the specified level. For instance, if biodiesel is blended at a temperature less than 10°F above its cloud point, it will not mix well with diesel, causing a rich mixture in one portion of the tank and a lean mix‐

#### *4.3.1.3. Liquid phase*


#### *4.3.1.4. Critical point*


#### *4.3.1.5. Gaseous phase*


#### *4.3.2. Miscellaneous*


#### **5. Biofuel blending**

It is important that when you are purchasing fuel you make sure it is high quality by meet‐ ing all ASTM specifications. Fuel that is off specification on just one of the ASTM standards can not only cause serious engine problems, but it can void engine warranties if it is deter‐ mined that the fuel caused damage. This can cause unnecessary costly repairs for vehicles/ equipment. To review specifications for diesel fuel, biodiesel and biodiesel blends, see the specifications in the Appendix. In an effort ensure that producers and marketers operate in a manner consistent with proper specifications, the National Biodiesel Accreditation Commis‐ sion created the BQ-9000 program in 2005. This voluntary program establishes quality sys‐ tems for producers and marketers of biodiesel in the areas of storage, sampling, testing, blending, shipping, distribution and fuel management practices. If purchasing B100 or a bio‐ diesel blend, ask if the biodiesel is from a BQ-9000 biodiesel producer/marketer. If you are unable to get fuel from a BQ-9000 producer/marketer, the next best thing is to verify with your supplier that the fuel meets all ASTM specifications.

In most cases the blending process takes place right at the terminal rack by a process called in-line blending. This is the preferred method because it ensures complete blending. In-line blending occurs when warm biodiesel is added to a stream of diesel fuel as it travels through a pipe or hose in such a way that the biodiesel and diesel fuel become thoroughly mixed by the turbulent movement. This product is sold directly to customers, petroleum jobbers or a distribution company for sale to customers.

The blend level (percentage of biodiesel in the biodieseldiesel mixture) determines many im‐ portant characteristics of the blended fuel. A higher‐than‐specified level of biodiesel may ex‐ ceed the engine manufacturer's recommended limitation, compromising the engine performance. A lower blend level of biodiesel may reduce the expected benefits, such asfuel lubricity and tail pipe emission. In addition, cloud point and pour point of biodiesel are usu‐ ally higher than that of diesel fuel, and a higher blend level makes the fuel unsuitable or dif‐ ficult to use in cold weather conditions. Engine injection timing can be adjusted based on the blend level in order to improve the engine emission and performance (Tat and Van Gerpen, 2003).

It has been reported that the actual biodiesel content of blended biodiesel fuel sold at gas stations can be significantly different from the nominal blend level. A 2% nominal blend has been found to actually contain anywhere from 0% to 8% biodiesel (Ritz and Croudace, 2005). There are several reasons why the actual blend level may differ from the specified level. For instance, if biodiesel is blended at a temperature less than 10°F above its cloud point, it will not mix well with diesel, causing a rich mixture in one portion of the tank and a lean mix‐ ture in another portion (NBB, 2005). Other reasons for the discrepancy may include profit‐ driven fraud and involuntary mixing of diesel into the blend to lower the overall blend level of biodiesel. Biodiesel is usually sold at a higher price than diesel fuel; therefore, the price of the fuel is dependent on the blend level. Knothe (2001) has shown that near‐infrared (NIR) spectroscopy and nuclear magnetic resonance (NMR) can be used to detect biodiesel blend levels. However, the NMR method depends on the biodiesel fatty acid profile; hence, knowledge of the biodiesel feedstock is required before this method can be used. In addi‐ tion, using NMR only to detect blend level may not be cost effective. For NIR spectroscopy, Knothe suggested using wavelengths around 1665 nm or 2083 to 2174\_nm. Since aromatic compounds produce strong and sharp infrared bands due to their relatively rigid molecular structure and diesel fuels have varying amounts of aromatics between 20% and 35% (Song et al., 2000), the absorbance of a blend may not directly correlate to the percentage of biodie‐ sel. The absorbance is defined as the logarithm of the radiation intensities ratio, that is, be‐ fore and after being absorbed by a sample.

Diesel fuel is distilled from crude petroleum, which is composed primarily of hydrocarbons of the paraffinic, naphthenic, and aromatic classes. Each class contains a very broad range of molecular weights. One of the features of diesel fuel is the presence of 20% to 35% aromatic compounds by weight. Aromatics are a class of hydrocarbons that are characterized by a stable chemical ring structure. They are determined primarily by the composition of the crude oil feed, which is usually selected based on considerations of availability and cost (Chevron, 2006). On the other hand, biodiesel is a mixture of fatty acid esters. Fatty acids with 16 to 22 carbon chain lengths are predominant in oils and fats. The resulting mixture of fatty acid esters depends on the kind of feedstock used. Neat biodiesel contains essentially no aromatic compounds.

**Figure 12.** UV absorbance spectra of soy methyl ester and No. 2 diesel blend diluted 1:2915 in *n*-heptane.

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**Figure 13.** Absorbance of diluted biodiesel‐diesel blends from different feedstocks at 260 nm wavelength (MME = mustard methyl esters, CME\_=canola methyl esters, RME = rapeseed methyl esters, MEE = mustard ethyl esters, and

SME = soybean methyl esters).

The presence of aromatics in diesel and their absence in biodiesel creates the possibility of distinguishing these two fuels using ultraviolet spectroscopy. Benzene, the simplest aromat‐ ic compound, has maximum absorption at 278 nm (Zawadzki et al., 2007). Biodiesel, which is esters of long‐chain fatty acids when adequately diluted in *n*‐heptane, has negligible ab‐ sorbance compared to the aromatics at the same frequency. Hence, differences in biodiesel feedstocks will have a minimal impact on absorbance at this wavelength. The ultraviolet (UV) range between 200 and 380 nm is also referred to as near‐UV. In general, light sources, filters, and detectors are less expensive for this vicinity of the spectrum than for IR at 8621 nm, as used by the CETANE 2000. Hence, near‐UV spectroscopy may present a low‐cost al‐ ternative method for biodiesel blend level sensing (Figure 12 and 13).

#### **6. Material balance of biofuel product**

Biomass conversion plant has many components which are connected each other. Material and energy flow among the components, therefore we should grasp the detail of the balance (Figures 13-16). If there is a choke point, the flow stagnation causes to the troubles of opera‐ tion and low efficiency of the performance. (Masami UENO, University of Ruyku, Faculty of Agriculture, Okinawa, Japan).

**Figure 12.** UV absorbance spectra of soy methyl ester and No. 2 diesel blend diluted 1:2915 in *n*-heptane.

**Figure 13.** Absorbance of diluted biodiesel‐diesel blends from different feedstocks at 260 nm wavelength (MME = mustard methyl esters, CME\_=canola methyl esters, RME = rapeseed methyl esters, MEE = mustard ethyl esters, and SME = soybean methyl esters).

**Figure 14.** Material balance and energy balance.

**Figure 16.** Material and energy balance in direct combustion

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**Figure 17.** Material and energy balance in RDF production

**Figure 15.** Material and energy balance in biodiesl fuel production

**Figure 16.** Material and energy balance in direct combustion

**Figure 17.** Material and energy balance in RDF production

#### **7. Conclusion**

The different kind of biomass considered as main source for biofuel (diesel-methane, etha‐ nol, compost –etc). The cost of extraction and blending is very effective point for use of bio‐ mass in addition to ability for use of all part from biomass as multipurpose.

[11] Ma F.; M.A. Hanna, Biodiesel production: a review, Bioresour. Technol. 70 (1999) 1–5.

Biofuel: Sources, Extraction and Determination

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477

[12] Meher LC, Sagar DV, Naik SN. Techical aspects of biodiesel production by transes‐

[13] Mittelbach M. Diesel fuel derived from vegetable oils, VI: specifications and quality

[14] Nagai, S. and Nishio, N., In "Handbook of Heat and Mass Transfer, vol. 3 Catalysis, Kinetics and Reactor Engineering" Ed. Cheremisinoff, N.P., 701-752 (1986) Gulf Pub‐

[15] NBB. 2005. Biodiesel cold weather blending study. Jefferson City, Mo.: National Bio‐

[16] Predojevic, ZJ. (2008).The production of biodiesel from waste frying oils: A compari‐

[17] Ritz, G. P., and M. C. Croudace. 2005. Biodiesel or FAME (fatty acid methyl ester): Mid‐infrared determination of ester concentration in diesel fuel. Houston, Tex.: Pe‐

[18] Shalaby, EA (2011). Algal Biomass and Biodiesel Production, Biodiesel - Feedstocks and Processing Technologies, Margarita Stoytcheva and Gisela Montero (Ed.), ISBN: 978-953-307-713-0, InTech, Available from: http://www.intechopen.com/articles/

[19] Shalaby, EA and El-Gendy. NS. (2012). Two steps alkaline transesterification of waste cooking oil and quality assessment of produced biodiesel. International Journal of

[20] Sharma YC, Singh B, Upadhyay SN. Advancements in development and characteri‐

[21] Šiler-Marinkovic´ SS, Tomaševic´ VA. Transesterification of sunflower oil in situ.

[22] Song, C., C. S. Hsu, and I. Mochida. 2000. Introduction to chemistry of diesel fuel. In

[23] Tat, M. E., and J. H. Van Gerpen. 2003. Biodiesel blend detection with a fuel composi‐

[24] Tomasevic V. A. and Siler-Marinkovic S. S. "Methanolysis of used frying oil" Fuel

[25] Vicente G.; M. Martínez, J. Aracil, Optimisation of integrated biodiesel production. Part I. A study of the biodiesel purity and yield, Bioresour. Technol. 98 (2007). 1724–

Chemistry of Diesel Fuels, 1‐60. New York, N.Y.: Taylor and Francis.

terification-a review. Renew Sust Energ Rev 2004:1–21.

control of biodisel. Bioresour Technol 1996;56:7–11.

son of different purification steps. Fuel 87 : 522–3528.

show/title/algal-biomass-and-biodiesel-production

zation of biodiesel: a review. Fuel 2008;87:2355–73.

tion sensor. Applied Eng. in Agric. 19(2): 125‐131.

Chemical and Biochemical Sciences. IJCBS, 1(2012): 30-35.

lishing Corn., Houston, London, Paris, Tokyo.

troleum Analyzer Company (PAC).

Fuel 1998;77:1389–91.

Process Technol. 81: 1-6 (2003).

1733.

diesel Board.

#### **Author details**

Emad A. Shalaby

Biochemistry Dept., Facult. of Agriculture, University of Ruyku, Cairo University, Egypt

#### **References**


[26] Zawadzki, A.; Shrestha, D. S.; He, B. (2007). Biodiesel Blend Level Detection Using Ultraviolet Absorption Spectra. American Society of Agricultural and Biological En‐ gineers, 50(4): 1349-1353.

**Chapter 16**

**Conversion of Oil Palm Empty Fruit Bunch to Biofuels**

Crude palm oil production is reaching 48.99 million metric tonnes per year globally in 2011 and Southeast Asia is the main contributor, with Indonesia accounting for 48.79%, Malaysia 36.75%, and Thailand 2.96% (Palm Oil Refiners Association of Malaysia, 2011). Oil palm is a multi-purpose plantation and it is also an intensive producer of biomass. Accompanying the production of one kg of palm oil, approximately 4 kg of dry biomass are produced. One third of the oil palm biomass is oil palm empty fruit bunch (OPEFB) and the other two

The supply of oil palm biomass and its processing by-products are found to be seven times that of natural timber [4]. Besides producing oils and fats, there are continuous interests in using oil palm biomass as the source of renewable energy. Among the oil palm biomass, OPEFB is the most often investigated biomass for biofuel production. Traditionally, OPEFB is used for pow‐ er and steam utilization in the palm oil mills, and is used for composting and soil mulch. Di‐ rect burning of OPEFB causes environmental problems due the incomplete combustion and

> © 2013 Geng; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

© 2013 Geng; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

distribution, and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

Anli Geng

**1. Introduction**

http://dx.doi.org/10.5772/53043

thirds are oil palm trunks and fronds [1-3].

**Figure 1.** Oil palm and oil palm empty fruit bunch.

## **Conversion of Oil Palm Empty Fruit Bunch to Biofuels**

### Anli Geng

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53043

#### **1. Introduction**

Crude palm oil production is reaching 48.99 million metric tonnes per year globally in 2011 and Southeast Asia is the main contributor, with Indonesia accounting for 48.79%, Malaysia 36.75%, and Thailand 2.96% (Palm Oil Refiners Association of Malaysia, 2011). Oil palm is a multi-purpose plantation and it is also an intensive producer of biomass. Accompanying the production of one kg of palm oil, approximately 4 kg of dry biomass are produced. One third of the oil palm biomass is oil palm empty fruit bunch (OPEFB) and the other two thirds are oil palm trunks and fronds [1-3].

**Figure 1.** Oil palm and oil palm empty fruit bunch.

The supply of oil palm biomass and its processing by-products are found to be seven times that of natural timber [4]. Besides producing oils and fats, there are continuous interests in using oil palm biomass as the source of renewable energy. Among the oil palm biomass, OPEFB is the most often investigated biomass for biofuel production. Traditionally, OPEFB is used for pow‐ er and steam utilization in the palm oil mills, and is used for composting and soil mulch. Di‐ rect burning of OPEFB causes environmental problems due the incomplete combustion and

© 2013 Geng; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Geng; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the release of very fine particles of ash. The conversion of OPEFB to biofuels, such as syngas, ethanol, butanol, bio-oil, hydrogen and biogas etc., might be a good alternative and have less environmental footprint. The properties of OPEFB is listed in Table 1 [5].

**2. Pretreatment**

untreated OPEFB [7].

Similar to all other lignocellulosic biomass, OPEFB are composed of cellulose, hemicellulose and lignin. Among the three components, lignin has the most complex structure, making it recalcitrant to both chemical and biological conversion. Pretreatment of OPEFB is therefore necessary to open its structure and increase its digestibility and subsequently the degree of conversion. Pretreatment of OPEFB can be classified as biological pretreatment, physical

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For biological pretreatment, oxidizing enzymes and white-rot fungi were used to degrade the lignin content in OPEFB. For example, enzymes such as lignin peroxidase (LiP) and manganese peroxidase (MnP) was used to pretreat OPEFB for fast pyrolysis and the bio-oil yield was improved from 20% to 30% [6]. Syafwina et al. used white-rot fungi to pretreat OPEFB and the saccharification efficiency was improved by 150% compared to that of the

Among all the pretreatment methods, chemical pretreatment is most often reported for OPEFB. Two-stage dilute acid hydrolysis [8], alkali pretreatment [9], sequential dilute acid and alkali pretreatment [10], alkali and hydrogen peroxide pretreatment [11], sequential al‐ kali and phosphoric acid pretreatment [10], aqueous ammonia [12], and solvent digestion [5] were used to increase the digestibility of OPEFB. Among all the chemical methods investi‐ gated, alkali pretreatment seemed to be the most effective. Umikalsom et al. autoclaved the milled OPEFB in the presence of 2% NaOH and 85% hydrolysis yield was obtained [13]. Han and his colleagues investigated NaOH pretreatment of OPEFB for bioethanol produc‐ tion [9]. The optimal conditions were found to be 127.64°C, 22.08 min, and 2.89 mol/L NaOH. With a cellulase loading of 50 FPU /g cellulose a total glucose conversion rate (TGCR) of 86.37% was obtained using the Changhae Ethanol Multi Explosion (CHEMEX) fa‐ cility. The effectiveness of alkali pretreatment might be attributed to its capability in lignin degradation. Mission et al. investigated the alkali treatment followed H2O2 treatment and found that almost 100% lignin degradation was obtained when OPEFB was firstly treated with dilute NaOH and subsequently with H2O2 [11]. This confirmed the lignin degradation

Besides alkali pretreatment, physical-chemical pretreatment such as ammonium fibre explo‐ sion (AFEX) [14] and superheated steam [15] were also shown to be effective in the increase of OPEFB digestibility. Hydrolysis efficiency of 90% and 66% were obtained, respectively.

Thermo-chemical conversion is one of the important routes to obtain fuels from lignocellulo‐ sic biomass. Thermo-chemical conversion of biomass involves heating the biomass materials in the absence of oxygen to produce a mixture of gas, liquid and solid. Such products can be used as fuels after further conversion or upgrading. Generally, thermo-chemical processes

pretreatment, chemical pretreatment, and physical-chemical pretreatment.

by NaOH and its enhancement by the addition of H2O2.

**3. Thermo-chemical conversion**


Notes: na - not available.

**Table 1.** Properties of oil palm empty fruit bunch

While all the OPEFB components can be converted to biofuels, such as bio-oil and syngas through thermo-chemical conversion, cellulose and hemicellulose can be hydrolysed to sug‐ ars and subsequently be fermented to biofuels such as ethanol, butanol, and biogas etc. Al‐ though many scientists around the world are developing technologies to generate biofuels from OPEFB, to-date, none of such technologies has been commercialized. This is largely due to the recalcitrance of the OPEFB and therefore the complexity of the conversion tech‐ nologies making biofuels from OPEFB less competitive than the fossil-based fuels. Continual efforts in R&D are still necessary in order to bring such technology to commercialization. The aim of this paper is to review the progress and challenges of the OPEFB conversion technologies so as to help expedite the OPEFB conversion technology development.

#### **2. Pretreatment**

Similar to all other lignocellulosic biomass, OPEFB are composed of cellulose, hemicellulose and lignin. Among the three components, lignin has the most complex structure, making it recalcitrant to both chemical and biological conversion. Pretreatment of OPEFB is therefore necessary to open its structure and increase its digestibility and subsequently the degree of conversion. Pretreatment of OPEFB can be classified as biological pretreatment, physical pretreatment, chemical pretreatment, and physical-chemical pretreatment.

For biological pretreatment, oxidizing enzymes and white-rot fungi were used to degrade the lignin content in OPEFB. For example, enzymes such as lignin peroxidase (LiP) and manganese peroxidase (MnP) was used to pretreat OPEFB for fast pyrolysis and the bio-oil yield was improved from 20% to 30% [6]. Syafwina et al. used white-rot fungi to pretreat OPEFB and the saccharification efficiency was improved by 150% compared to that of the untreated OPEFB [7].

Among all the pretreatment methods, chemical pretreatment is most often reported for OPEFB. Two-stage dilute acid hydrolysis [8], alkali pretreatment [9], sequential dilute acid and alkali pretreatment [10], alkali and hydrogen peroxide pretreatment [11], sequential al‐ kali and phosphoric acid pretreatment [10], aqueous ammonia [12], and solvent digestion [5] were used to increase the digestibility of OPEFB. Among all the chemical methods investi‐ gated, alkali pretreatment seemed to be the most effective. Umikalsom et al. autoclaved the milled OPEFB in the presence of 2% NaOH and 85% hydrolysis yield was obtained [13]. Han and his colleagues investigated NaOH pretreatment of OPEFB for bioethanol produc‐ tion [9]. The optimal conditions were found to be 127.64°C, 22.08 min, and 2.89 mol/L NaOH. With a cellulase loading of 50 FPU /g cellulose a total glucose conversion rate (TGCR) of 86.37% was obtained using the Changhae Ethanol Multi Explosion (CHEMEX) fa‐ cility. The effectiveness of alkali pretreatment might be attributed to its capability in lignin degradation. Mission et al. investigated the alkali treatment followed H2O2 treatment and found that almost 100% lignin degradation was obtained when OPEFB was firstly treated with dilute NaOH and subsequently with H2O2 [11]. This confirmed the lignin degradation by NaOH and its enhancement by the addition of H2O2.

Besides alkali pretreatment, physical-chemical pretreatment such as ammonium fibre explo‐ sion (AFEX) [14] and superheated steam [15] were also shown to be effective in the increase of OPEFB digestibility. Hydrolysis efficiency of 90% and 66% were obtained, respectively.

#### **3. Thermo-chemical conversion**

Thermo-chemical conversion is one of the important routes to obtain fuels from lignocellulo‐ sic biomass. Thermo-chemical conversion of biomass involves heating the biomass materials in the absence of oxygen to produce a mixture of gas, liquid and solid. Such products can be used as fuels after further conversion or upgrading. Generally, thermo-chemical processes have lower reaction time required (a few seconds or minutes) and the superior ability to de‐ stroy most of the organic compounds. These mainly include biomass pyrolysis and biomass gasification. Recently, thermo-chemical pretreatment of biomass, such as torrefaction was introduced to upgrade biomass for more efficient biofuel production [16-17].

compact equipment requirements with a relatively small footprint, accurate combustion control, and high thermal efficiency. The main challenge in gasification is enabling the py‐ rolysis and gas reforming reactions to take place using the minimum amount of energy and

Ogi et al. used an entrained-flow gasifier for OPEFB gasification at 900°C [22]. During gasifi‐ cation with H2O alone, the carbon conversion rate was greater than 95% (C-equivalent), and hydrogen-rich gas with a composition suitable for liquid fuel synthesis ([H2]/[CO] = 1.8–3.9) was obtained. The gasification rate was improved to be greater than 99% when O2 was add‐ ed to H2O; however, under these conditions, the gas composition was less suitable for liquid fuel synthesis due to the increase of CO2 amount. Thermogravimetric (TG) analysis suggest‐ ed that OPEFB decomposed easily, especially in the presence of H2O and/or O2, suggesting that OPEFB is an ideal candidate for biomass gasification. Lahijani and Zainal investigated OPEFB gasification in a pilot-scale air-blown fluidized bed reactor [23]. The effect of bed temperature (650–1050°C) on gasification performance was studied and the gasification re‐ sults were compared to that of sawdust. Results showed that at 1050°C, OPEFB had almost equivalent gas yield and cold gas efficiency compared with saw dust, however, with low maximal heating values and higher carbon conversion. In addition, it was realized that ag‐ glomeration was the major issue in OPEFB gasification at high temperatures. This can be overcome by lowering the temperature to 770 ± 20 °C. Mohammed et al. studied OPEFB gas‐ ification in a bench scale fluidized-bed reactor for hydrogen-rich gas production [24]. The total gas yield was enhanced greatly with the increase of temperature and it reached the maximum value (~92 wt.%) at 1000 °C with big portions of H2 (38.02 vol.%) and CO (36.36 vol.%). The feedstock particle size of 0.3–0.5 mm, was found to obtain a higher H2 yield

(ER) (0.25) was found to attain a higher H2 yield (27.31 vol.%) at 850 °C. Due to the low effi‐ ciency of bench scale gasification unit the system needs to be scaling-up. The cost analysis for scale-up EFB gasification unit showed that the hydrogen supply cost is \$2.11/kg OPEFB. Recently, a characterization and kinetic analysis was done by Mohammed et al. and it was found that a high content of volatiles (>82%) increased the reactivity of OPEFB, and more than 90% decomposed at 700 °C; however, a high content of moisture (>50%) and oxygen (>45%) resulted in a low calorific value [25]. The fuel characteristics of OPEFB are compara‐ ble to those of other biomasses and it can be considered a good candidate for gasification.

Torrefaction is a thermal conversion method of biomass in the low temperature range of 200-300 °C. Biomass is pretreated to produce a high quality solid biofuel that can be used for combustion and gasification [16-17]. It is based on the removal of oxygen from biomass to produce a fuel with increased energy density. Different reaction conditions (temperature, in‐ ert gas, reaction time) and biomass resources lead to the differences in solid, liquid and gas‐

Uemura et al. [16] studied the effect of torrefaction on the basic characteristics of oil palm emp‐ ty fruit bunches (EFB), mesocarp fibre and kernel shell as a potential source of solid fuel. It was

). The optimum equivalence ratio

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gasifier design is therefore important [21].

(33.93 vol.%), and higher LHV of gas product (15.26 MJ/m3

**3.3. OPEFB torrefaction**

eous products.

#### **3.1. OPEFB pyrolysis**

Pyrolysis is defined as the thermal degradation of the biomass materials in the absence of oxygen. It is normally conducted at moderate temperature (400 – 600°C) over a short period of retention time. Its products comprise of liquids (water, oil/tars), solids (charcoal) and gas‐ es (methane, hydrogen, carbon monoxide and carbon dioxide). The efficiency of pyrolysis and the amount of solid, liquid, and gaseous fractions formed largely depend on the process parameters such as pretreatment condition, temperature, retention time and type of reactors.

Misson et al investigated the effects of alkaline pretreatment using NaOH, Ca(OH)2, in con‐ junction with H2O2, on the catalytic pyrolysis of OPEFB [11]. They proved that consecutive addition of NaOH and H2O2 decomposed almost 100% of OPEFB lignin compared to 44% for the Ca(OH)2 and H2O2 system, while the exclusive use of NaOH and Ca(OH)2 could not alter lignin composition much. In addition, the pretreated OPEFB was catalytically pyro‐ lysed more efficiently than the untreated OPEFB samples under the same conditions.

Fast pyrolysis represents a potential route to upgrade the OPEFB waste to value-added fuels and renewable chemicals. For woody feedstock, temperatures around 400-600°C together with short vapour residence times (0.5-2 s) are used to obtain bio-oil yields of around 70%, along with char and gas yields of around 15% each. Sulaiman and Abdullah investigated fast pyrolysis of OPEFB using and bench top fluidized bed reactor with a nominal capacity of 150 g/L [18]. After extensive feeding trials, it was found that only particles between 250 and 355 m were easily fed. The maximum liquid and organics yields (55% total liquids) were obtained at 450°C. Higher temperature was more favourable for gas production and water content was almost constant in the range of temperature investigated. The maximum liquids yield and the minimum char yield were obtained at a residence time of 1.03 s. The pyrolysis liquids produced separated into two phases; a phase predominated by tarry or‐ ganic compounds (60%) and an aqueous phase (40%). The phase separated liquid product would represent a challenging fuel for boilers and engines, due to the high viscosity of the organics phase and the high water content of the aqueous phase. These could be overcome by upgrading. However, the by-product, charcoal, has been commercialized for quite some time. It is worth noting that the first pilot bio-oil plant by Genting Bio-oil has already started operation in Malaysia [19].

#### **3.2. OPEFB gasification**

Gasification process is an extension of the pyrolysis process except that it is conducted at elevated temperature range of 800–1300 °C so that it is more favourable for gas production [20]. The gas stream is mainly composed of methane, hydrogen, carbon monoxide, and car‐ bon dioxide. Biomass gasification offers several advantages, such as reduced CO2 emissions, compact equipment requirements with a relatively small footprint, accurate combustion control, and high thermal efficiency. The main challenge in gasification is enabling the py‐ rolysis and gas reforming reactions to take place using the minimum amount of energy and gasifier design is therefore important [21].

Ogi et al. used an entrained-flow gasifier for OPEFB gasification at 900°C [22]. During gasifi‐ cation with H2O alone, the carbon conversion rate was greater than 95% (C-equivalent), and hydrogen-rich gas with a composition suitable for liquid fuel synthesis ([H2]/[CO] = 1.8–3.9) was obtained. The gasification rate was improved to be greater than 99% when O2 was add‐ ed to H2O; however, under these conditions, the gas composition was less suitable for liquid fuel synthesis due to the increase of CO2 amount. Thermogravimetric (TG) analysis suggest‐ ed that OPEFB decomposed easily, especially in the presence of H2O and/or O2, suggesting that OPEFB is an ideal candidate for biomass gasification. Lahijani and Zainal investigated OPEFB gasification in a pilot-scale air-blown fluidized bed reactor [23]. The effect of bed temperature (650–1050°C) on gasification performance was studied and the gasification re‐ sults were compared to that of sawdust. Results showed that at 1050°C, OPEFB had almost equivalent gas yield and cold gas efficiency compared with saw dust, however, with low maximal heating values and higher carbon conversion. In addition, it was realized that ag‐ glomeration was the major issue in OPEFB gasification at high temperatures. This can be overcome by lowering the temperature to 770 ± 20 °C. Mohammed et al. studied OPEFB gas‐ ification in a bench scale fluidized-bed reactor for hydrogen-rich gas production [24]. The total gas yield was enhanced greatly with the increase of temperature and it reached the maximum value (~92 wt.%) at 1000 °C with big portions of H2 (38.02 vol.%) and CO (36.36 vol.%). The feedstock particle size of 0.3–0.5 mm, was found to obtain a higher H2 yield (33.93 vol.%), and higher LHV of gas product (15.26 MJ/m3 ). The optimum equivalence ratio (ER) (0.25) was found to attain a higher H2 yield (27.31 vol.%) at 850 °C. Due to the low effi‐ ciency of bench scale gasification unit the system needs to be scaling-up. The cost analysis for scale-up EFB gasification unit showed that the hydrogen supply cost is \$2.11/kg OPEFB. Recently, a characterization and kinetic analysis was done by Mohammed et al. and it was found that a high content of volatiles (>82%) increased the reactivity of OPEFB, and more than 90% decomposed at 700 °C; however, a high content of moisture (>50%) and oxygen (>45%) resulted in a low calorific value [25]. The fuel characteristics of OPEFB are compara‐ ble to those of other biomasses and it can be considered a good candidate for gasification.

#### **3.3. OPEFB torrefaction**

Torrefaction is a thermal conversion method of biomass in the low temperature range of 200-300 °C. Biomass is pretreated to produce a high quality solid biofuel that can be used for combustion and gasification [16-17]. It is based on the removal of oxygen from biomass to produce a fuel with increased energy density. Different reaction conditions (temperature, in‐ ert gas, reaction time) and biomass resources lead to the differences in solid, liquid and gas‐ eous products.

Uemura et al. [16] studied the effect of torrefaction on the basic characteristics of oil palm emp‐ ty fruit bunches (EFB), mesocarp fibre and kernel shell as a potential source of solid fuel. It was found that mesocarp fibre and kernel shell exhibited excellent energy yield values higher than 95%, whereas OPEFB, on the other hand, exhibited a rather poor yield of 56%. Torrefaction can also be done in the presence of oxygen. Uemura and his colleagues [17] carried out OPEFB tor‐ refaction in a fixed-bed tubular reactor in the presence of oxygen at varied oxygen concentra‐ tion. The mass yield decreased with increasing temperature and oxygen concentration, but was unaffected by biomass particle size. The energy yield decreased with increasing oxygen concentrations, however, was still between 85% and 95%. It was found that the oxidative torre‐ faction process occurred in two successive steps or via two parallel reactions, where one reac‐ tion is ordinary torrefaction, and the other is oxidation.

NaOH. Enzyme loading of 50 FPU/g cellulose resulted in 86.37% glucose conversion in their Changhae Ethanol Multi Explosion (CHEMEX) facility. An ethanol concentration of 48.54 g/L was obtained at 20% (w/v) pretreated biomass loading, along with simultaneous saccha‐ rification and fermentation (SSF) processes. This is so far the highest reported ethanol titre from OPEFB. Overall, 410.48 g of ethanol were produced from 3 kg of raw OPEFB in a single

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Jung and his colleagues tried aqueous ammonia soaking for the pretreatment of OPEFB and its conversion to ethanol [12]. Pretreated OPEFB at 60°C, 12 h, and 21% (w/w) aqueous am‐ monia, showed 19.5% and 41.4% glucose yields after 96h enzymatic hydrolysis using 15 and 60 FPU of cellulase per gram of OPEFB, respectively. An ethanol concentration of 18.6 g/L and a productivity of 0.11 g/L/h were obtained with the ethanol yield of 0.33 g ethanol/

Lau et al. successfully applied ammonia fibre expansion (AFEX) pretreatment for cellulosic ethanol production from OPEFB [14]. The sugar yield was close to 90% after enzyme formu‐ lation optimization. Post-AFEX size reduction is required to enhance the sugar yield possi‐ bly due to the high tensile strength (248 MPa) and toughness (2,000 MPa) of palm fibre compared to most cellulosic feedstock. Interestingly, the water extract from AFEX-pretreat‐ ed OPEFB at 9% solids loading is highly fermentable and up to 65 g/L glucose can be fer‐

OPEFB was also used for butanol production. Noomtim and Cheirsilp (2011) studied buta‐ nol production from OPEFB using *Clostridium acetobutylicum* [27]. Again, the pretreatment by alkali was found to be the most suitable method to prepare OPEFB for enzymatic hydrol‐ ysis. 1.262 g/L ABE (acetone, butanol and ethanol) was obtained in RCM medium containing 20 g/L sugar obtained from cellulase hydrolysed OPEFB. Ibrahim et al also investigated OPEFB as the potential substrate for ABE production [28]. Higher ABE yield was obtained from treated OPEFB when compared to using a glucose-based medium using *Clostridium bu‐ tyricum* EB6. A higher ABE level was obtained at pH 6.0 with a concentration of 3.47 g/L.

Nieves et al. investigated biogas production using OPEFB. OPEFB was pre-treated using NaOH and phosphoric acid [29]. When 8% NaOH (60 min) was used for the pretreatment, 100% improvement in the yield of methane production was observed and 97% of the theo‐ retical value of methane production was achieved under such pretreatment condition. The results showed that the carbohydrate content of OPEFB could be efficiently converted to methane under the anaerobic digestion process. O-Thong et al. investigated the effect of pre‐ treatment methods for improved biodegradability and biogas production of oil palm empty fruit bunches (EFB) and its co-digestion with palm oil mill effluent (POME) [30]. The maxi‐ mum methane potential of OPEFB was 202 mL CH4/g VS-added corresponding to 79.1 m3 CH4/ton OPEFB with 38% biodegradability. Co-digestion of treated OPEFB by NaOH pre‐ soaking and hydrothermal treatment with POME resulted in 98% improvement in methane yield comparing with co-digesting untreated OPEFB. The maximum methane production of co-digestion treated OPEFB with POME was 82.7 m3 CH4/ton of mixed treated OPEFB and POME (6.8:1), corresponding to methane yield of 392 mL CH4/g VS-added. The study

mented to ethanol within 24 h without the supplement of nutrients.

The accumulated acid (5 to 13 g/L) had inhibitory effects on cell growth.

run, using the CHEMEX 50 L reactor.

glucose.

#### **3.4. Summary**

The analysis of thermo-chemical conversion of OPEFB suggests that gasification is the most suitable thermo-chemical route for OPEFB conversion to biofuels. It has the highest carbon conversion (>90%) and biofuel yield. Due to the high viscosity and high water content of py‐ rolysis products, application of bio-oil as a biofuel is still very challenging. Compared to other oil palm residues, such as oil palm kernel, due to its high water content, OPEFB may not be a good candidate for solid fuels even after torrefaction pretreatment.

#### **4. Bioconversion**

Bioconversion of lignocellulosic biomass to fuels involves three major steps: 1) pretreatmentto effectively broken the biomass structure and release the biomass components i.e. cellu‐ lose, hemicellulose, and lignin, and therefore increase the digestibility of the biomass; 2) enzymatic hydrolysis – to hydrolyse cellulose and hemicellulose and produce fermentable sugar, such as glucose, xylose etc.; 3) fermentation – to convert the biomass hydrolysate sug‐ ars to the desired products. OPEFB was intensively investigated as a potential substrate for the production of biofuels, such as ethanol, butanol, and biogas etc. Among the biofuels pro‐ duced through bioconversion of OPEFB, cellulosic ethanol is the most intensively studied.

Two stage dilute acid hydrolysis was applied for OPEFB bioconversion to ethanol, 135.94 g xylose/kg OPEFB and 62.70 g glucose/kg OPEFB were produced in the first stage and 2nd stage, respectively [8]. They were then fermented to ethanol using *Mucor indicus* and *Saccha‐ romyces cerevisiae*, respectively, and the corresponding ethanol yields were 0.45 and 0.46 g ethanol/g sugar.

Alkali is the most often used pretreatment chemical for cellulosic ethanol production from OPEFB. Kassim et al. pretreated OPEFB using 1% NaOH followed by mild acid (0.7% H2SO4) hydrolysis and enzymatic saccharification [26]. A total of 16.4 g/L of glucose and 3.85 g/L of xylose were obtained during enzymatic saccharification. The OPEFB hydrolysate was fermented with *Saccharomyces cerevisiae* and an ethanol yield of 0.51 g/g yield was obtained, suggesting that OPEFB is a potential substrate for cellulosic ethanol production. Han and his colleagues investigated ethanol production through pilot scale alkali pretreatment and fer‐ mentation [9]. The best pretreatment condition was 127.64 °C, 22.08 min, and 2.89 mol/L NaOH. Enzyme loading of 50 FPU/g cellulose resulted in 86.37% glucose conversion in their Changhae Ethanol Multi Explosion (CHEMEX) facility. An ethanol concentration of 48.54 g/L was obtained at 20% (w/v) pretreated biomass loading, along with simultaneous saccha‐ rification and fermentation (SSF) processes. This is so far the highest reported ethanol titre from OPEFB. Overall, 410.48 g of ethanol were produced from 3 kg of raw OPEFB in a single run, using the CHEMEX 50 L reactor.

Jung and his colleagues tried aqueous ammonia soaking for the pretreatment of OPEFB and its conversion to ethanol [12]. Pretreated OPEFB at 60°C, 12 h, and 21% (w/w) aqueous am‐ monia, showed 19.5% and 41.4% glucose yields after 96h enzymatic hydrolysis using 15 and 60 FPU of cellulase per gram of OPEFB, respectively. An ethanol concentration of 18.6 g/L and a productivity of 0.11 g/L/h were obtained with the ethanol yield of 0.33 g ethanol/ glucose.

Lau et al. successfully applied ammonia fibre expansion (AFEX) pretreatment for cellulosic ethanol production from OPEFB [14]. The sugar yield was close to 90% after enzyme formu‐ lation optimization. Post-AFEX size reduction is required to enhance the sugar yield possi‐ bly due to the high tensile strength (248 MPa) and toughness (2,000 MPa) of palm fibre compared to most cellulosic feedstock. Interestingly, the water extract from AFEX-pretreat‐ ed OPEFB at 9% solids loading is highly fermentable and up to 65 g/L glucose can be fer‐ mented to ethanol within 24 h without the supplement of nutrients.

OPEFB was also used for butanol production. Noomtim and Cheirsilp (2011) studied buta‐ nol production from OPEFB using *Clostridium acetobutylicum* [27]. Again, the pretreatment by alkali was found to be the most suitable method to prepare OPEFB for enzymatic hydrol‐ ysis. 1.262 g/L ABE (acetone, butanol and ethanol) was obtained in RCM medium containing 20 g/L sugar obtained from cellulase hydrolysed OPEFB. Ibrahim et al also investigated OPEFB as the potential substrate for ABE production [28]. Higher ABE yield was obtained from treated OPEFB when compared to using a glucose-based medium using *Clostridium bu‐ tyricum* EB6. A higher ABE level was obtained at pH 6.0 with a concentration of 3.47 g/L. The accumulated acid (5 to 13 g/L) had inhibitory effects on cell growth.

Nieves et al. investigated biogas production using OPEFB. OPEFB was pre-treated using NaOH and phosphoric acid [29]. When 8% NaOH (60 min) was used for the pretreatment, 100% improvement in the yield of methane production was observed and 97% of the theo‐ retical value of methane production was achieved under such pretreatment condition. The results showed that the carbohydrate content of OPEFB could be efficiently converted to methane under the anaerobic digestion process. O-Thong et al. investigated the effect of pre‐ treatment methods for improved biodegradability and biogas production of oil palm empty fruit bunches (EFB) and its co-digestion with palm oil mill effluent (POME) [30]. The maxi‐ mum methane potential of OPEFB was 202 mL CH4/g VS-added corresponding to 79.1 m3 CH4/ton OPEFB with 38% biodegradability. Co-digestion of treated OPEFB by NaOH pre‐ soaking and hydrothermal treatment with POME resulted in 98% improvement in methane yield comparing with co-digesting untreated OPEFB. The maximum methane production of co-digestion treated OPEFB with POME was 82.7 m3 CH4/ton of mixed treated OPEFB and POME (6.8:1), corresponding to methane yield of 392 mL CH4/g VS-added. The study showed that there was a great potential to co-digestion treated OPEFB with POME for bio‐ energy production.

zation. Pyrolysis, on the other hand, produced very complex bio-oil with high viscosity and water content, making it challenging for commercialization. However, charcoal from OPEFB pyrolysis can be a potential commercial product. Compared to other palm oil residues, such as oil palm kernel, OPEFB may not be a good candidate for solid fuel production, even after

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Biological conversion of OPEFB is another route to obtain biofuels from OPEFB. Cellulosic ethanol production was most intensively studied and around 50 g/L titre was obtained with 20% (w/v) biomass loading through NaOH pretreatment. AFEX also showed potential in OPEFB pretreatment and a glucose yield of 90% was obtained with 9% biomass loading. The water extract of the AFEX pretreated OPEFB was highly fermentable. OPEFB also showed some promising preliminary results in ABE (acetone, butanol and ethanol) and biogas produc‐ tion; however, further investigation is necessary to enhance OPEFB conversion potentials in

For both thermo-chemical and biological conversion of OPEFB, pretreatment technology is the key for the process cost. Although alkali pretreatment is effective, scaling-up the process re‐ quires huge amount of acid to neutralize the base in the pretreatment solution. In addition, be‐ fore alkali pretreatment, OPEFB should be milled to reduce its size, which is energyconsuming. Steam explosion is effective for a lot of lignocellulosic biomass, however not much research was found on its pretreatment of OPEFB. A cost-effective pretreatment is the key for the successful commercialization of OPEFB conversion technologies for biofuel production.

The. authors are grateful for the financial support to the research on cellulosic ethanol by the Science and Engineering Research Council of the Agency for Science, Technology and Re‐

School of Life Sciences and Chemical Technology, Ngee Ann Polytechnic, Singapore

[1] Husin M, Ramli R, Mokhtar A, Hassan WHW, Hassan K, Mamat R. Research and de‐ velopment of oil palm biomass utilization in wood-based industries. Palm Oil Devel‐

torrefaction pretreatment due to its high water content and low energy capacity.

these areas.

**Acknowledgement**

search (A\*STAR), Singapore.

Address all correspondence to: gan2@np.edu.sg

opment 2002; 36: 1-5.

**Author details**

Anli Geng

**References**

In summary, OPEFB has been frequently investigated as a substrate for biofuel production through bioconversion. Cellulosic ethanol production was most intensively investigated and the highest ethanol titre of 48.54 g/L was obtained through alkali pretreatment in a pilot scale reactor [9]. Although not much research has been done for ABE and biogas production, the few reports summarized in this paper suggest that OPEFB is also potential substrate for butanol and biogas production. Throughout the reports reviewed, alkali-based pretreatment methods, such as NaOH alone, NaOH followed by acid, and ammonium fibre expansion (AFEX) pretreatment are the most effective in enhancing OPEFB digestibility.

#### **5. Conclusion**

In conclusion, OPEFB is the most potential renewable resource for biofuel production in South‐ east Asia. It can be converted to biofuels through thermo-chemical or biological conversion. Pretreatment of OPEFB is necessary for both routes of conversion and alkali pretreatment is the most effective. A summary of OPEFB conversion technology is shown in Fig. 2.

**Figure 2.** Biofuel production from OPEFB.

Among the studies on OPEFB thermo-chemical conversion, it seems that gasification is the most suitable approach to obtain bioenergy from OPEFB and has potential in commerciali‐ zation. Pyrolysis, on the other hand, produced very complex bio-oil with high viscosity and water content, making it challenging for commercialization. However, charcoal from OPEFB pyrolysis can be a potential commercial product. Compared to other palm oil residues, such as oil palm kernel, OPEFB may not be a good candidate for solid fuel production, even after torrefaction pretreatment due to its high water content and low energy capacity.

Biological conversion of OPEFB is another route to obtain biofuels from OPEFB. Cellulosic ethanol production was most intensively studied and around 50 g/L titre was obtained with 20% (w/v) biomass loading through NaOH pretreatment. AFEX also showed potential in OPEFB pretreatment and a glucose yield of 90% was obtained with 9% biomass loading. The water extract of the AFEX pretreated OPEFB was highly fermentable. OPEFB also showed some promising preliminary results in ABE (acetone, butanol and ethanol) and biogas produc‐ tion; however, further investigation is necessary to enhance OPEFB conversion potentials in these areas.

For both thermo-chemical and biological conversion of OPEFB, pretreatment technology is the key for the process cost. Although alkali pretreatment is effective, scaling-up the process re‐ quires huge amount of acid to neutralize the base in the pretreatment solution. In addition, be‐ fore alkali pretreatment, OPEFB should be milled to reduce its size, which is energyconsuming. Steam explosion is effective for a lot of lignocellulosic biomass, however not much research was found on its pretreatment of OPEFB. A cost-effective pretreatment is the key for the successful commercialization of OPEFB conversion technologies for biofuel production.

### **Acknowledgement**

The. authors are grateful for the financial support to the research on cellulosic ethanol by the Science and Engineering Research Council of the Agency for Science, Technology and Re‐ search (A\*STAR), Singapore.

### **Author details**

#### Anli Geng

Address all correspondence to: gan2@np.edu.sg

School of Life Sciences and Chemical Technology, Ngee Ann Polytechnic, Singapore

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**Chapter 17**

**Coproducts of Biofuel Industries in Value-Added**

**Biomaterials Uses: A Move Towards a Sustainable**

Worldpopulationis expectedtogrownearly9billionin2040andeventuallyincreases theglobal energy demand by 30% compared to current conception [1]. The issues related to increasing trend of crude oil cost, depleting source of fossil fuels and emerging threat on greenhouse gas emissionsareleadingtheglobalenergysectortoundergoafundamentaltransformationtowards renewable energy sources [1-2]. As the result, a main focus is motivated on renewable energy technologies that are basedonsolar, windandbiofuels.Intransportationpoint ofview, biofuels receive extensive attention due to their versatility in storage and refilling. Both bioethanol and biodiesel come together as biofuel currently produced from renewable resources through two different pathways. In some countries like Brazil, biofuels are produced and marketed at competitive cost comparedtopetroleum-basedfuels employingexistingtechnology[3-4].They also carry following advantages comparing to petro fuels; (i) create significantly less pollu‐ tants (SOx and NOx), which also mitigates CO2 emission, (ii) biodegradable nature lead to the less environmentalleak risk and(iii)provides betterlubricant effect, whichenhances the engine life[5].Inaddition,theseemergingbiofueltechnologieswillbeexpectedtocreatemoreeconomic benefits to agriculture sectors and new rural job opportunities. Moreover, biofuels are attrac‐ tive options for future energy demand since they can be produced domestically by many countries while the respective retail and consumer infrastructure needs minimum modifica‐

However, biofuel foresees a challenging journey to benefit from its highest potentials and to guarantee a viable future. Primarily, it needs policy support and commercialization. At the

> © 2013 Vivekanandhan et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Vivekanandhan et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

S. Vivekanandhan, N. Zarrinbakhsh, M. Misra and

Additional information is available at the end of the chapter

tion; so does the existing engine and fueling technology [6].

**Bioeconomy**

A. K. Mohanty

**1. Introduction**

http://dx.doi.org/10.5772/55382

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