**Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil Derived Biodiesel and Ultra Low Sulphur Diesel**

Raghu Betha, Rajasekhar Balasubramanian and Guenter Engling

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53476

### **1. Introduction**

A ground breaking invention in 1893 by Rudolf Diesel (Diesel Engine – named after him) made a mark in the world of internal combustion engines; his engine was the first one to prove that fuel could be ignited without a spark. Since this invention, diesel engines have been widely used in various applications such as automobiles, agriculture, ships, electricity generators, construction equipment etc., all over the world. Diesel engines were proved to be very efficient in terms of delivering the required energy levels for their use at very low operating and maintenance costs when compared to gasoline engines. However, diesel en‐ gines now pose a serious threat to human health and adversely impact the urban air quality (Sydbom et al., 2001). Diesel engine exhaust contains a host of harmful substances including airborne particulate matter (PM), carbon soot, toxic metals, polycyclic aromatic hydrocar‐ bons (PAHs), nitrogen oxides which induce ozone formation, carbon monoxide, carbon di‐ oxide, volatile organic compounds and other compounds such as formaldehyde and acrolein (EPA, 2002). Of these pollutants, PM from diesel exhaust is of great concern because of a number of reasons: (1) Diesel engines are known to be the largest source of PM from motor vehicles. Two thirds of PM emitted from mobile sources are from diesel vehicles (EPA, 2002); (2) Human exposure to diesel exhaust particles (DEP) is high as these particles are emitted at ground level unlike that of smoke stacks. United Stated of Environmental Pro‐ tection Agency (USEPA) reported that 83% of people living in the USA are exposed to con‐ centrated diesel emissions from sources such as highways, heavy industries, construction

© 2013 Betha 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 Betha 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.

sites, bus and truck depots etc (EPA, 1999); (3) The freshly emitted DEP includes ultra fine particles (UFPs, aerodynamic diameter (AED) < 100 nm). These particles can bypass the nat‐ ural defense of respiratory tract and enter deep into the alveolar region of respiratory sys‐ tem from where they could enter into blood stream (Oberdorster, 2001); (4) The particulatebound soluble organic compounds such as PAHs, nitro-PAHs and transition metals are considered mutagenic or carcinogenic. PM from diesel exhaust is listed as a ''likely Carcino‐ gen,'' citing cancer risk in the range of one in 1000 to one in 100,000 people for each micro‐ gram of annual average exposure (EPA, 2002).

tween 2000 and 2005. According to National Biodiesel Board (NBB) in USA alone 460 mil‐ lion gallons of biodiesel were sold in 2007, 700 million gallons in 2008, and 802 million gallons in 2011, showing a tremendous raise from 2 million gallons sold in 2000. This move from fossil fuels to bio-fuels as a power source is also caused by the economic consequences due to stringent regulations ((EN-590, 2004) in Europe and (ASTM-D-975, 2006) in USA) im‐ posed on the fuels used in transportation. The notable restriction includes reducing sulfur content in the fuel which increased the investment cost of oil companies and the final fuel price which drive the nations to develop their own reserves indigenously and decrease their

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

463

Biodiesel is compatible with conventional petroleum based-diesel and can be completely blended with diesel in any proportion. The chemical composition and several properties of biodiesel make it an attractive option over traditional diesel. Biodiesel has higher cetane number, lubricity, combustion efficiency, biodegradability and lower sulfur and aromatic content (Fazal et al., 2011; Demirbas, 2008). In contrast, there are also unfavorable properties in biodiesel such as being more prone to oxidation, lower heating value, and higher cloud and pour points (Szulczyk and McCarl, 2010). Majority of biodiesel is being produced from soybean, rapeseed, and palm oils. Even though most of the biodiesel feedstock is renewable, competition with food supply has become a serious concern recently because certain feed‐ stocks appear to be edible oils (Januan and Ellis, 2010; Mercer-Blackman et al., 2007). There‐ fore, alternative feedstocks such as non-edible oils, algae oils, and waste oils have arisen to prominence in recent years. Biodiesel produced from transesterification of waste cooking oil (WCO) is one of the most attractive automotive fuels to be used in place of petroleum diesel because of the added advantages over other types of biodiesel. WCO reuse eliminates the need for disposal, thus alleviating the environment and human health issues associated with waste oil disposal (Giracol et al., 2011). The lower cost of WCO feedstock can also help to make biodiesel competitive in price with conventional diesel (Meng et al., 2008). Many stud‐ ies have been initiated to investigate the impacts of biodiesel made from several feedstocks including WCO on particulate emissions as compared to diesel fuel (Chung et al., 2008; Lin et al., 2011a; Lapuerta et al., 2008, Turrio-Baldassari et al., 2004; Durbin et al., 2007). An ap‐ parent decrease in PM emissions with the biodiesel content can be considered as an almost unanimous trend (Lapuerta et al.,2008). Most of the research on emissions from biodiesel is targeted towards physical properties of PM such as particulate mass, number concentrations and their size distributions. Apparently very little information is available pertaining to the health and environmental impacts of particulate emissions of biodiesel due to paucity of da‐

**2. Phyiscal characterization of PM emitted from WCOB and ULSD**

Conventional regulatory procedure involving dilution tunnel sampling and filter collection proved to be satisfactory for collection of PM from diesel engines a decade ago. However, in the current scenario, the low emission rate (~1mg/km) of PM from modern-era diesel en‐ gines places difficulties in sampling through traditional procedures because of their high de‐

dependence on Middle East countries for fuel.

ta on their chemical composition.

Apart from the health impacts, DEP also has potential environmental impacts. Black car‐ bon or soot from diesels affects cloud cover and is a significant contributor to atmospheric warming (Hansen et al., 2000). In view of these concerns and also to meet the current and future regulation standards imposed by local environmental protection agencies, a large number of researchers have conducted research to reduce the diesel particulate levels by various methods such as introducing new engine designs (Guerrassi and Dupraz 1998; Park, et al., 2004), development of particle trap systems and after-treatment devices (Sta‐ matelos 1997), improving the fuel quality (Kaufmann, et al., 1999). Despite these develop‐ ments over many decades which improved the emission quality of diesels without any doubt, diesel engines still represent a significant source of PM. Holmen and Ayala (2002) reported that the use of particle trap systems reduces total particle number concentration by 10 to 100 times from diesel exhaust, but also found that the use of particle trap-equip‐ ped diesel engines may sometimes result in elevated nanoparticle (diameter < 50 nm) emissions. Also, there is an ongoing debate on whether the diesel engine can be modified and improved continuously down to meet the future regulation standards without eco‐ nomic impact. It is believed that developments on engine design needed to meet upcom‐ ing regulations would increase the costs and eventually gasoline vehicles could take the place of diesel vehicles (Pischinger, 1996).

As an alternative strategy to improve emission quality of diesels, the option of replacing die‐ sel or petroleum based fuels by renewable bio-fuels is gaining popularity in recent years. Bi‐ odiesel (also known as fatty acid alkyl esters), an alternative fuel derived through transesterification process from vegetable oils or animal fats, has received much attention as a result of renewed interest in renewable energy sources for reducing particulate and green‐ house gas (GHG) emissions from diesel engines. In addition, it also helps in alleviating the depletion of fossil fuel reserves (Pahl, 2008; Janauan and Ellis, 2010). Biodiesel is reported to be carbon neutral because of the lower net carbon dioxide production (Ferella et al., 2010; Gunvachi et al., 2007; Carraretto et al., 2004), making it an important fuel source in the era of climate change. Another main driving force for biodiesel is the lower emissions of PM, CO, hydrocarbon, aromatic and polycyclicaromatic compounds (Xue et al., 2011, Atadashi et al., 2010). In view of these advantages, usage of biodiesel is increasing rapidly. This is reflected in government policies such as partial detaxation, investment in production and research of biodiesel by many countries that include USA, Brazil, European Union, South East Asian and other countries all over the world. With these increased awareness and governmental policies of different countries, annual production of biodiesel nearly tripled globally be‐ tween 2000 and 2005. According to National Biodiesel Board (NBB) in USA alone 460 mil‐ lion gallons of biodiesel were sold in 2007, 700 million gallons in 2008, and 802 million gallons in 2011, showing a tremendous raise from 2 million gallons sold in 2000. This move from fossil fuels to bio-fuels as a power source is also caused by the economic consequences due to stringent regulations ((EN-590, 2004) in Europe and (ASTM-D-975, 2006) in USA) im‐ posed on the fuels used in transportation. The notable restriction includes reducing sulfur content in the fuel which increased the investment cost of oil companies and the final fuel price which drive the nations to develop their own reserves indigenously and decrease their dependence on Middle East countries for fuel.

sites, bus and truck depots etc (EPA, 1999); (3) The freshly emitted DEP includes ultra fine particles (UFPs, aerodynamic diameter (AED) < 100 nm). These particles can bypass the nat‐ ural defense of respiratory tract and enter deep into the alveolar region of respiratory sys‐ tem from where they could enter into blood stream (Oberdorster, 2001); (4) The particulatebound soluble organic compounds such as PAHs, nitro-PAHs and transition metals are considered mutagenic or carcinogenic. PM from diesel exhaust is listed as a ''likely Carcino‐ gen,'' citing cancer risk in the range of one in 1000 to one in 100,000 people for each micro‐

Apart from the health impacts, DEP also has potential environmental impacts. Black car‐ bon or soot from diesels affects cloud cover and is a significant contributor to atmospheric warming (Hansen et al., 2000). In view of these concerns and also to meet the current and future regulation standards imposed by local environmental protection agencies, a large number of researchers have conducted research to reduce the diesel particulate levels by various methods such as introducing new engine designs (Guerrassi and Dupraz 1998; Park, et al., 2004), development of particle trap systems and after-treatment devices (Sta‐ matelos 1997), improving the fuel quality (Kaufmann, et al., 1999). Despite these develop‐ ments over many decades which improved the emission quality of diesels without any doubt, diesel engines still represent a significant source of PM. Holmen and Ayala (2002) reported that the use of particle trap systems reduces total particle number concentration by 10 to 100 times from diesel exhaust, but also found that the use of particle trap-equip‐ ped diesel engines may sometimes result in elevated nanoparticle (diameter < 50 nm) emissions. Also, there is an ongoing debate on whether the diesel engine can be modified and improved continuously down to meet the future regulation standards without eco‐ nomic impact. It is believed that developments on engine design needed to meet upcom‐ ing regulations would increase the costs and eventually gasoline vehicles could take the

As an alternative strategy to improve emission quality of diesels, the option of replacing die‐ sel or petroleum based fuels by renewable bio-fuels is gaining popularity in recent years. Bi‐ odiesel (also known as fatty acid alkyl esters), an alternative fuel derived through transesterification process from vegetable oils or animal fats, has received much attention as a result of renewed interest in renewable energy sources for reducing particulate and green‐ house gas (GHG) emissions from diesel engines. In addition, it also helps in alleviating the depletion of fossil fuel reserves (Pahl, 2008; Janauan and Ellis, 2010). Biodiesel is reported to be carbon neutral because of the lower net carbon dioxide production (Ferella et al., 2010; Gunvachi et al., 2007; Carraretto et al., 2004), making it an important fuel source in the era of climate change. Another main driving force for biodiesel is the lower emissions of PM, CO, hydrocarbon, aromatic and polycyclicaromatic compounds (Xue et al., 2011, Atadashi et al., 2010). In view of these advantages, usage of biodiesel is increasing rapidly. This is reflected in government policies such as partial detaxation, investment in production and research of biodiesel by many countries that include USA, Brazil, European Union, South East Asian and other countries all over the world. With these increased awareness and governmental policies of different countries, annual production of biodiesel nearly tripled globally be‐

gram of annual average exposure (EPA, 2002).

462 Biodiesel - Feedstocks, Production and Applications

place of diesel vehicles (Pischinger, 1996).

Biodiesel is compatible with conventional petroleum based-diesel and can be completely blended with diesel in any proportion. The chemical composition and several properties of biodiesel make it an attractive option over traditional diesel. Biodiesel has higher cetane number, lubricity, combustion efficiency, biodegradability and lower sulfur and aromatic content (Fazal et al., 2011; Demirbas, 2008). In contrast, there are also unfavorable properties in biodiesel such as being more prone to oxidation, lower heating value, and higher cloud and pour points (Szulczyk and McCarl, 2010). Majority of biodiesel is being produced from soybean, rapeseed, and palm oils. Even though most of the biodiesel feedstock is renewable, competition with food supply has become a serious concern recently because certain feed‐ stocks appear to be edible oils (Januan and Ellis, 2010; Mercer-Blackman et al., 2007). There‐ fore, alternative feedstocks such as non-edible oils, algae oils, and waste oils have arisen to prominence in recent years. Biodiesel produced from transesterification of waste cooking oil (WCO) is one of the most attractive automotive fuels to be used in place of petroleum diesel because of the added advantages over other types of biodiesel. WCO reuse eliminates the need for disposal, thus alleviating the environment and human health issues associated with waste oil disposal (Giracol et al., 2011). The lower cost of WCO feedstock can also help to make biodiesel competitive in price with conventional diesel (Meng et al., 2008). Many stud‐ ies have been initiated to investigate the impacts of biodiesel made from several feedstocks including WCO on particulate emissions as compared to diesel fuel (Chung et al., 2008; Lin et al., 2011a; Lapuerta et al., 2008, Turrio-Baldassari et al., 2004; Durbin et al., 2007). An ap‐ parent decrease in PM emissions with the biodiesel content can be considered as an almost unanimous trend (Lapuerta et al.,2008). Most of the research on emissions from biodiesel is targeted towards physical properties of PM such as particulate mass, number concentrations and their size distributions. Apparently very little information is available pertaining to the health and environmental impacts of particulate emissions of biodiesel due to paucity of da‐ ta on their chemical composition.

### **2. Phyiscal characterization of PM emitted from WCOB and ULSD**

Conventional regulatory procedure involving dilution tunnel sampling and filter collection proved to be satisfactory for collection of PM from diesel engines a decade ago. However, in the current scenario, the low emission rate (~1mg/km) of PM from modern-era diesel en‐ gines places difficulties in sampling through traditional procedures because of their high de‐ tection limits. Nor is this traditional method agreeable to recent regulations aimed at in-use emissions monitoring or to the vast variety of off road applications. A workshop was organ‐ ized by Coordinating Research Council (CRC) in 2002 to discuss possible changes to meas‐ urement of DPM, and it is proposed that particle number-based methods potentially allow detection at very low levels with consistency provided formation of nucleation mode parti‐ cles can be avoided (CRC, 2002). However, it is a difficult task to establish particle numberbased standards and a standard methodology for measurement because of the sensitivity in detection, and great variability of nano-sized particles in engine exhaust. The European PMP (Particle measurement Program) and many other organizations including USEPA are working towards improving the methodology for measurement of solid particles to supple‐ ment the traditional mass method. A well-designed dilution tunnel satisfying the above re‐ quirements and reducing losses is the first step for this purpose.

nucleation processes. Typical dilution tunnels for particualte sampling from engines are de‐

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

**a.** To reduce the particle concentration in raw exhaust to a concentration that can be han‐

**b.** To reduce the temperatures to an adequate value usually close to ambient temperature;

The PM concentration in raw exhaust varies with engine model, design, applied load and other parameters. A rough estimate of the total number concentrations of diesel engines is in

designed to capture/monitor the particles in nanoscale that are abundantly present in to‐ day's diesel exhaust. These sampling instruments are highly sensitive, fragile and are relia‐ ble. Heavy loading of PM can easily disrupt the configuration, damage crucial systems leading to either inaccurate data, or render the equipment to be useless. So, it is required that the concentrations be brought down well below the instrument's maximum capacity.

tures can damage the charger columns and sensitive electrode plates used for detecting nanoparticles. Also, collection of PM on filter media from hot raw exhaust can alter the chemical composition of PM by inducing chemical reaction between the collected particles and filter media. Current regulation, for example the one used by the USEPA, requires that, PM be collected on filter media after the exhaust has been diluted and cooled to a tempera‐

Engine exhaust contains both gaseous phase and particle phase pollutants. Because of lower volatility and saturation coefficient some organic compounds and other precursor gases such as sulfur dioxide either condense onto the pre-existing particle surface altering their size (diameters), or nucleate to form new particles affecting number concentration. Also, particles can coagulate during dilution changing both the diameter and number of particles. Impact of these processes is very uncertain as they change dramatically during dilution and sampling (Kittelson, 1998) and thus makes comparisons from different sources difficult. It is therefore recommended that the dilution tunnels be designed to minimize or eliminate nu‐

Particles are lost during transfer of exhaust from a tail pipe to sampling instruments and during dilution due to particle – wall interactions. These losses include mechanical losses such as inertial impaction, gravitational settling, electrostatic deposition, and due to diffu‐

~109 cm-3. The present day sampling equipment and monitoring devices are

C, and such high tempera‐

http://dx.doi.org/10.5772/53476

465

**d.** To reduce the losses of particulate matter during dilution and sampling.

A typical temperature of raw exhaust is in the range of 200~4000

**c. Reduction in nucleation /condensation and coagulation**

cleation, condensation and coagulation (Burtscher, 2005).

signed to meet the following requirements.

dled by the measurement system;

**a. Reducing the PM concentration**

**b. Reduction in exhaust temperature**

C (CFR, 2001).

**d. Reducing losses during sampling**

the range of 108

ture below 520

**c.** To control the nucleation/condensation processes;

Typically, DEP are agglomerates of many primary spherical particles of about 15-40 nm di‐ ameter. Airborne particles differ in size, composition, solubility and therefore also in their toxicological properties. It is a well-established fact that the current standards on diesel en‐ gine emissions not only improved the engine technology but also the fuel quality. These modern day engines emit particles of very low diameter (Su et al., 2004). Most of the particle mass exists in the accumulation mode in the diameter range of 0.1-0.3 μm (Kittelson, 1998). A large part of UFPs go unnoticed when only mass concentration is used as a metric. UFPs contribute a small fraction to the mass concentration of ambient aerosol particles, but may contribute disproportionately to their toxicity because of their high number concentration and surface area, high deposition efficiency in the pulmonary region, and high propensity to penetrate the epithelium (Donaldson et al., 2000).

### **2.1. Design of dilution tunnel**

A dilution tunnel is a closed and controlled chamber where hot exhaust from engines, in‐ dustrial stacks etc is mixed with dilution gas (usually ambient air) prior to sampling. Dilu‐ tion sampling was originally used to characterize fine particle emissions from combustion sources because it simulates the rapid cooling and dilution that occurs as exhaust mixes with the atmosphere. Several researchers have developed dilution tunnels over decades for this purpose; one of the popular dilution sampling systems to simulate atmospheric condi‐ tions is CALTECH design (Hildemann et al., 1989). However dilution tunnels can also be used to freeze the size distribution by proper design criteria to avoid unwanted nucleation, condensation and coagulation. These dilution tunnels are developed for consistent measure‐ ment of particle number concentrations (PNC) from diesel engines.

The design of the sampling and dilution system determines largely what is measured later. Burtscher (2005) suggested in his review paper that the solid nanoparticles from the exhaust are closely related to health impacts and thus solid fractions of the exhaust should be sepa‐ rated from the volatile fraction and be studied for better understanding of health effects. Al‐ so, Kittelson (1998) identified that nucleation and coagulation of volatile fraction changes dramatically during dilution and sampling making it difficult to design a standard. Thus, one of the major issues in dilution sampling of engine exhaust is to decrease or eliminate nucleation processes. Typical dilution tunnels for particualte sampling from engines are de‐ signed to meet the following requirements.


### **a. Reducing the PM concentration**

tection limits. Nor is this traditional method agreeable to recent regulations aimed at in-use emissions monitoring or to the vast variety of off road applications. A workshop was organ‐ ized by Coordinating Research Council (CRC) in 2002 to discuss possible changes to meas‐ urement of DPM, and it is proposed that particle number-based methods potentially allow detection at very low levels with consistency provided formation of nucleation mode parti‐ cles can be avoided (CRC, 2002). However, it is a difficult task to establish particle numberbased standards and a standard methodology for measurement because of the sensitivity in detection, and great variability of nano-sized particles in engine exhaust. The European PMP (Particle measurement Program) and many other organizations including USEPA are working towards improving the methodology for measurement of solid particles to supple‐ ment the traditional mass method. A well-designed dilution tunnel satisfying the above re‐

Typically, DEP are agglomerates of many primary spherical particles of about 15-40 nm di‐ ameter. Airborne particles differ in size, composition, solubility and therefore also in their toxicological properties. It is a well-established fact that the current standards on diesel en‐ gine emissions not only improved the engine technology but also the fuel quality. These modern day engines emit particles of very low diameter (Su et al., 2004). Most of the particle mass exists in the accumulation mode in the diameter range of 0.1-0.3 μm (Kittelson, 1998). A large part of UFPs go unnoticed when only mass concentration is used as a metric. UFPs contribute a small fraction to the mass concentration of ambient aerosol particles, but may contribute disproportionately to their toxicity because of their high number concentration and surface area, high deposition efficiency in the pulmonary region, and high propensity to

A dilution tunnel is a closed and controlled chamber where hot exhaust from engines, in‐ dustrial stacks etc is mixed with dilution gas (usually ambient air) prior to sampling. Dilu‐ tion sampling was originally used to characterize fine particle emissions from combustion sources because it simulates the rapid cooling and dilution that occurs as exhaust mixes with the atmosphere. Several researchers have developed dilution tunnels over decades for this purpose; one of the popular dilution sampling systems to simulate atmospheric condi‐ tions is CALTECH design (Hildemann et al., 1989). However dilution tunnels can also be used to freeze the size distribution by proper design criteria to avoid unwanted nucleation, condensation and coagulation. These dilution tunnels are developed for consistent measure‐

The design of the sampling and dilution system determines largely what is measured later. Burtscher (2005) suggested in his review paper that the solid nanoparticles from the exhaust are closely related to health impacts and thus solid fractions of the exhaust should be sepa‐ rated from the volatile fraction and be studied for better understanding of health effects. Al‐ so, Kittelson (1998) identified that nucleation and coagulation of volatile fraction changes dramatically during dilution and sampling making it difficult to design a standard. Thus, one of the major issues in dilution sampling of engine exhaust is to decrease or eliminate

quirements and reducing losses is the first step for this purpose.

ment of particle number concentrations (PNC) from diesel engines.

penetrate the epithelium (Donaldson et al., 2000).

**2.1. Design of dilution tunnel**

464 Biodiesel - Feedstocks, Production and Applications

The PM concentration in raw exhaust varies with engine model, design, applied load and other parameters. A rough estimate of the total number concentrations of diesel engines is in the range of 108 ~109 cm-3. The present day sampling equipment and monitoring devices are designed to capture/monitor the particles in nanoscale that are abundantly present in to‐ day's diesel exhaust. These sampling instruments are highly sensitive, fragile and are relia‐ ble. Heavy loading of PM can easily disrupt the configuration, damage crucial systems leading to either inaccurate data, or render the equipment to be useless. So, it is required that the concentrations be brought down well below the instrument's maximum capacity.

### **b. Reduction in exhaust temperature**

A typical temperature of raw exhaust is in the range of 200~4000 C, and such high tempera‐ tures can damage the charger columns and sensitive electrode plates used for detecting nanoparticles. Also, collection of PM on filter media from hot raw exhaust can alter the chemical composition of PM by inducing chemical reaction between the collected particles and filter media. Current regulation, for example the one used by the USEPA, requires that, PM be collected on filter media after the exhaust has been diluted and cooled to a tempera‐ ture below 520 C (CFR, 2001).

### **c. Reduction in nucleation /condensation and coagulation**

Engine exhaust contains both gaseous phase and particle phase pollutants. Because of lower volatility and saturation coefficient some organic compounds and other precursor gases such as sulfur dioxide either condense onto the pre-existing particle surface altering their size (diameters), or nucleate to form new particles affecting number concentration. Also, particles can coagulate during dilution changing both the diameter and number of particles. Impact of these processes is very uncertain as they change dramatically during dilution and sampling (Kittelson, 1998) and thus makes comparisons from different sources difficult. It is therefore recommended that the dilution tunnels be designed to minimize or eliminate nu‐ cleation, condensation and coagulation (Burtscher, 2005).

### **d. Reducing losses during sampling**

Particles are lost during transfer of exhaust from a tail pipe to sampling instruments and during dilution due to particle – wall interactions. These losses include mechanical losses such as inertial impaction, gravitational settling, electrostatic deposition, and due to diffu‐ sion (Kittelson and Johnson 1991). Apart from mechanical losses particles are also lost due to thermophoretic deposition. These losses can impact the particle number concentration and size distribution.

The primary design objective of the dilution tunnel is to make sure that what is released at tail pipe is measured at sampling instruments. In other words, it is designed to minimize/ eliminate dilution artifacts, reduce losses, avoid nucleation to preserve the number and size distribution of particles as it is emitted from tail pipe. Before describing the actual design, it is useful to understand the theoretical basis underlying the design. The following sections 2.1.1 and 2.1.2 describe the important mechanisms that play a key role in altering the physi‐ cal and chemical properties of particles during dilution and the measures taken to prevent such changes. Section 2.1.3 presents actual design of the dilution tunnel.

### *2.1.1. Nucleation, condensation an coagulation*

Concentration of an inert species (Ci ) when diluted is given by (Kerminen and Wexler 1995).

$$\mathbf{C}\_{i} - \mathbf{C}\_{i,A} = f(\mathbf{C}\_{i,E} - \mathbf{C}\_{i,A}) \tag{1}$$

H2SO4-NH3 system (Korhonen et al., 1999). Precursor gas, sulfur dioxide, is oxidized to form

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

The critical value (*Ccrit* ) for the gas phase concentration of sulfuric acid required for binary nucleation to take place is given by the following formula (Jackervoirol and Mirabel, 1989).

cal ratio *H*2*SO*4(*g*)/ *Ccrit* becomes greater than 1, nucleation (gas-particle conversion) occurs instantaneously, giving birth to fresh nuclei in another log-normal distribution; these are called dilution-induced nuclei mode particles. From eq (5), it is clear that critical concentra‐ tion is a function of temperature. When the temperature of diluted exhaust is high, the criti‐ cal concentration required for nucleation tends to increase exponentially. Thus, it is recommended to dilute the hot exhaust with heated air rather than the conventional way of diluting the exhaust with air at ambient temperature. Also, Zhang and Wexler (2004) stud‐ ied the viability of sulfuric acid induced nucleation and the coupling effect of condensation and nucleation by simulating various cases and reported two important findings: (1) As sur‐ face area of combustion induced particles increases, the critical ratio drops and in extreme cases nucleation is totally quenched. This is not to say that supersaturated mixture is not formed, but the sulfuric acid is condensed onto the surface area of particles; (2) Extremely rapid dilution leads to super-saturation of nucleating species and thus nucleation. The possi‐

The vapor pressure for volatile compounds is proportional to its temperature. Vapor pres‐

*Rf T <sup>E</sup>*

Close to tail pipe, the temperature of exhaust far exceeds the ambient temperature, and there‐ fore equation (2) reduces to (T α f). As a result, a decrease in temperature leads to an exponen‐ tial decrease in vapor pressures, and the highly super-saturated vapors could make the time scale of condensation very short as 0.1 sec. Another factor important for condensation is parti‐ cle surface area; by reducing the available particle surface area, condensation can be quenched.

) (6)

*<sup>p</sup>* <sup>0</sup> *<sup>α</sup>*exp ( - <sup>∆</sup> *<sup>H</sup>*

( ) ( ) ( ) 2 23 SO g + ½ O g SO g ® (3)

http://dx.doi.org/10.5772/53476

467

( ) ( ) ( ) 3 2 24 SO g + H O g H SO g ® (4)

0.16exp(0.1 3.5 27.7) *Ccrit* = -- *T rh* (5)

, T is Temperature in Kelvin, rh is scaled between 0-1. When the criti‐

trioxide which gets converted to sulfate with water vapor.

bility of nucleation becomes lower if the dilution is smooth.

sure is related to dilution factor by (Zhang and Wexler 2004)

where *Ccrit* is in μg/m3

**b. Condensation**

where, *Ci*,*E*and *Ci*,*A* are concentrations in the exhaust and ambient air respectively, and *f* is dilution factor. Dilution factor simply means when the exhaust dilutes, a small parcel of air contains a certain fraction of the original exhaust and the remaining fraction is ambient air. That fraction of original exhaust in the air parcel is the dilution factor (*f*).

Temperature of an air parcel also changes in similar manner.

$$T\_- - T\_A = f(T\_E - T\_A) \tag{2}$$

where, TE and TA are the exhaust and ambient temperature, respectively.

#### **a. Nucleation**

Nucleation and condensation go hand in hand. Nucleation of nanoparticles from the diesel exhaust takes place as the exhaust cools during the dilution process (Abdul-Khalek et al., 1999). When partial pressure is much higher than vapor pressure of nucleating species, they undergo phase transformation. At the same time, due to their low volatility and the exis‐ tence of large surface area of particles, sulfuric acid and many organic compounds can also condense quickly on the particles. However, Zhang and Wexler (2002) reported that nuclea‐ tion favors compounds with both low volatility and low-molar volume in the condensed phase. High carbon number organics which usually possess very low vapor pressure, but significantly large condensed-phase molar volume are less likely to be the nucleating species than sulfuric acid (Zhang and Wexler 2004). Although it is still not clear about the nuclea‐ tion mechanism from SO2, it is widely believed that nucleation occurs through binary nucle‐ ation of water-sulfuric acid system (Kulmala et al., 1990) or ternary nucleation of WaterH2SO4-NH3 system (Korhonen et al., 1999). Precursor gas, sulfur dioxide, is oxidized to form trioxide which gets converted to sulfate with water vapor.

$$\text{SO}\_2(\text{g}) \text{}^\text{+} \uplus \text{O}\_2(\text{g}) \to \text{SO}\_3(\text{g}) \tag{3}$$

$$\text{SO}\_3(\text{g}) \text{ + H}\_2\text{O} \text{ (g)} \rightarrow \text{H}\_2\text{SO}\_4(\text{g}) \tag{4}$$

The critical value (*Ccrit* ) for the gas phase concentration of sulfuric acid required for binary nucleation to take place is given by the following formula (Jackervoirol and Mirabel, 1989).

$$C\_{crit} = 0.16 \exp(0.1T - 3.5rh - 27.7) \tag{5}$$

where *Ccrit* is in μg/m3 , T is Temperature in Kelvin, rh is scaled between 0-1. When the criti‐ cal ratio *H*2*SO*4(*g*)/ *Ccrit* becomes greater than 1, nucleation (gas-particle conversion) occurs instantaneously, giving birth to fresh nuclei in another log-normal distribution; these are called dilution-induced nuclei mode particles. From eq (5), it is clear that critical concentra‐ tion is a function of temperature. When the temperature of diluted exhaust is high, the criti‐ cal concentration required for nucleation tends to increase exponentially. Thus, it is recommended to dilute the hot exhaust with heated air rather than the conventional way of diluting the exhaust with air at ambient temperature. Also, Zhang and Wexler (2004) stud‐ ied the viability of sulfuric acid induced nucleation and the coupling effect of condensation and nucleation by simulating various cases and reported two important findings: (1) As sur‐ face area of combustion induced particles increases, the critical ratio drops and in extreme cases nucleation is totally quenched. This is not to say that supersaturated mixture is not formed, but the sulfuric acid is condensed onto the surface area of particles; (2) Extremely rapid dilution leads to super-saturation of nucleating species and thus nucleation. The possi‐ bility of nucleation becomes lower if the dilution is smooth.

### **b. Condensation**

sion (Kittelson and Johnson 1991). Apart from mechanical losses particles are also lost due to thermophoretic deposition. These losses can impact the particle number concentration and

The primary design objective of the dilution tunnel is to make sure that what is released at tail pipe is measured at sampling instruments. In other words, it is designed to minimize/ eliminate dilution artifacts, reduce losses, avoid nucleation to preserve the number and size distribution of particles as it is emitted from tail pipe. Before describing the actual design, it is useful to understand the theoretical basis underlying the design. The following sections 2.1.1 and 2.1.2 describe the important mechanisms that play a key role in altering the physi‐ cal and chemical properties of particles during dilution and the measures taken to prevent

where, *Ci*,*E*and *Ci*,*A* are concentrations in the exhaust and ambient air respectively, and *f* is dilution factor. Dilution factor simply means when the exhaust dilutes, a small parcel of air contains a certain fraction of the original exhaust and the remaining fraction is ambient air.

Nucleation and condensation go hand in hand. Nucleation of nanoparticles from the diesel exhaust takes place as the exhaust cools during the dilution process (Abdul-Khalek et al., 1999). When partial pressure is much higher than vapor pressure of nucleating species, they undergo phase transformation. At the same time, due to their low volatility and the exis‐ tence of large surface area of particles, sulfuric acid and many organic compounds can also condense quickly on the particles. However, Zhang and Wexler (2002) reported that nuclea‐ tion favors compounds with both low volatility and low-molar volume in the condensed phase. High carbon number organics which usually possess very low vapor pressure, but significantly large condensed-phase molar volume are less likely to be the nucleating species than sulfuric acid (Zhang and Wexler 2004). Although it is still not clear about the nuclea‐ tion mechanism from SO2, it is widely believed that nucleation occurs through binary nucle‐ ation of water-sulfuric acid system (Kulmala et al., 1990) or ternary nucleation of Water-

) when diluted is given by (Kerminen and Wexler 1995).

, ,, ( ) *C C fC C i iA iE iA* -= - (1)

( ) *A EA T T fT T* -= - (2)

such changes. Section 2.1.3 presents actual design of the dilution tunnel.

That fraction of original exhaust in the air parcel is the dilution factor (*f*).

where, TE and TA are the exhaust and ambient temperature, respectively.

Temperature of an air parcel also changes in similar manner.

*2.1.1. Nucleation, condensation an coagulation*

Concentration of an inert species (Ci

466 Biodiesel - Feedstocks, Production and Applications

size distribution.

**a. Nucleation**

The vapor pressure for volatile compounds is proportional to its temperature. Vapor pres‐ sure is related to dilution factor by (Zhang and Wexler 2004)

$$\left(p^{0}\,\alpha \exp\left(\cdot \frac{\Delta H}{R\_{f}T\_{E}}\right)\right) \tag{6}$$

Close to tail pipe, the temperature of exhaust far exceeds the ambient temperature, and there‐ fore equation (2) reduces to (T α f). As a result, a decrease in temperature leads to an exponen‐ tial decrease in vapor pressures, and the highly super-saturated vapors could make the time scale of condensation very short as 0.1 sec. Another factor important for condensation is parti‐ cle surface area; by reducing the available particle surface area, condensation can be quenched.

### **c. Coagulation**

Coagulation of particles during dilution occurs either due to turbulent shear, or due to Brownian coagulation. Zhang and Wexler (2004) evaluated coagulation through turbulent shear which has a time scale of *τts* = *ρ<sup>p</sup>* /( 48 *m* ^ *<sup>p</sup> <sup>ε</sup><sup>k</sup>* / <sup>120</sup>*v* and found that *τts* for turbulent shear is approximately 1018 sec, because these tiny particles have such small cross sectional area that shear is insufficient to bring them together. The only mechanism is through Brow‐ nian coagulation and it is very insignificant when compared to other mechanisms.

temperature to avoid thermophoretic deposition of particles onto the walls of the dilution tunnel. In stage 2, some portion of the diluted exhaust from the primary dilution tunnel was transferred to the secondary dilution tunnel. During the primary dilution, vapor pressures of volatile compounds decreased, allowing the secondary dilution with cold dilution air without condensing the volatile components. At this stage, the exhaust was mixed with di‐ lution air at ambient temperature to bring down the temperature of the hot exhaust to ambi‐ ent temperature for sampling. The completely diluted exhaust was then directed to particle measuring instruments. The dilution ratio was calculated by measuring the CO2 concentra‐

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

469

A two stage dilution is adopted, firstly to prevent rapid dilution, a dilution is not achieved instantaneously but gradually and secondly, to dilute the exhaust in two different environ‐ ments to reduce nucleation/condensation. In the primary dilution tunnel, since the exhaust is mixed with pre-heated air, time required for condensation is high comparable to the resi‐ dence time of the exhaust in dilution tunnel (1~2 sec). In the secondary dilution tunnel, since a small sample from the already diluted exhaust is drawn, the available surface area for con‐ densation is reduced by many times thus condensation is avoided in both stages of dilution.

tions in the raw exhaust, dilution air and diluted exhaust.

**Figure 1.** Schematic of a typical dilution tunnel.

### *2.1.2. Particle-wall interaction*

When the engine exhaust is sampled and passed through dilution tunnel and sampling tubes, particles are lost due to deposition on sampling surfaces. Particles are deposited through several ways which include mechanical (inertial, gravitational, electrostatic, diffu‐ sion) and thermal (thermophoretic losses). In their review of variability in particle emission measurements during heavy duty transient tests, Kittelson and Johnson (1991) discussed the impact of exhaust system temperatures on particle measurement and provided recommen‐ dations to minimize the effects on aerosol sampling. They calculated losses during the heavy-duty transient test for a typical test facility and found that the majority of particle loss (5%) is due to thermophoresis, whereas inertial, gravitational, electrostatic, and diffusion depositions put together resulted in a loss of 0.2%. Thermophoresis is a physical phenomen‐ on in which particles, subjected to a temperature gradient, move from high- to low tempera‐ ture zones. A temperature gradient is established during sampling and the dilution between exhaust and the sampling surfaces due to difference in their temperatures. This gradient re‐ sults in thermophoretic deposition of particles on sampling and dilution system surfaces. Eventually, these deposits are reentrained in the exhaust stream, or cause fouling of sam‐ pling surfaces. Reentrainment is unpredictable, and increases variability in mass measure‐ ments because of the increase in the number of coarse particles. These particles are not necessarily representative of diesel aerosol and make aerosol size distribution measure‐ ments more difficult. To avoid large differences in temperature between lines and exhaust gas, sampling lines should be fully insulated and kept to optimum size to reduce the resi‐ dence time of exhaust in the sampling lines. Short sampling lines also reduce gravitational and diffusional losses.

### *2.1.3. Dilution tunnel*

Figure 1 shows the schematic of a typical dilution tunnel used for particulate sampling from diesel engines. The engine exhaust was sampled through a sampling probe inserted into the main exhaust stream. The exhaust was then directed into a dilution tunnel, where the hot exhaust was mixed with a stream of pressurized, particle free, dry air in two stages using. In the first stage, the exhaust was transferred into the primary dilution tunnel, where the hot exhaust was mixed with a stream of pressurized particle free dry air preheated to a tempera‐ ture of close to the temperature of the exhaust, to avoid particle nucleation, condensation, etc. The primary dilution tunnel was also heated to a temperature close to engine exhaust temperature to avoid thermophoretic deposition of particles onto the walls of the dilution tunnel. In stage 2, some portion of the diluted exhaust from the primary dilution tunnel was transferred to the secondary dilution tunnel. During the primary dilution, vapor pressures of volatile compounds decreased, allowing the secondary dilution with cold dilution air without condensing the volatile components. At this stage, the exhaust was mixed with di‐ lution air at ambient temperature to bring down the temperature of the hot exhaust to ambi‐ ent temperature for sampling. The completely diluted exhaust was then directed to particle measuring instruments. The dilution ratio was calculated by measuring the CO2 concentra‐ tions in the raw exhaust, dilution air and diluted exhaust.

**Figure 1.** Schematic of a typical dilution tunnel.

**c. Coagulation**

468 Biodiesel - Feedstocks, Production and Applications

*2.1.2. Particle-wall interaction*

and diffusional losses.

*2.1.3. Dilution tunnel*

shear which has a time scale of *τts* = *ρ<sup>p</sup>* /( 48 *m*

Coagulation of particles during dilution occurs either due to turbulent shear, or due to Brownian coagulation. Zhang and Wexler (2004) evaluated coagulation through turbulent

shear is approximately 1018 sec, because these tiny particles have such small cross sectional area that shear is insufficient to bring them together. The only mechanism is through Brow‐

When the engine exhaust is sampled and passed through dilution tunnel and sampling tubes, particles are lost due to deposition on sampling surfaces. Particles are deposited through several ways which include mechanical (inertial, gravitational, electrostatic, diffu‐ sion) and thermal (thermophoretic losses). In their review of variability in particle emission measurements during heavy duty transient tests, Kittelson and Johnson (1991) discussed the impact of exhaust system temperatures on particle measurement and provided recommen‐ dations to minimize the effects on aerosol sampling. They calculated losses during the heavy-duty transient test for a typical test facility and found that the majority of particle loss (5%) is due to thermophoresis, whereas inertial, gravitational, electrostatic, and diffusion depositions put together resulted in a loss of 0.2%. Thermophoresis is a physical phenomen‐ on in which particles, subjected to a temperature gradient, move from high- to low tempera‐ ture zones. A temperature gradient is established during sampling and the dilution between exhaust and the sampling surfaces due to difference in their temperatures. This gradient re‐ sults in thermophoretic deposition of particles on sampling and dilution system surfaces. Eventually, these deposits are reentrained in the exhaust stream, or cause fouling of sam‐ pling surfaces. Reentrainment is unpredictable, and increases variability in mass measure‐ ments because of the increase in the number of coarse particles. These particles are not necessarily representative of diesel aerosol and make aerosol size distribution measure‐ ments more difficult. To avoid large differences in temperature between lines and exhaust gas, sampling lines should be fully insulated and kept to optimum size to reduce the resi‐ dence time of exhaust in the sampling lines. Short sampling lines also reduce gravitational

Figure 1 shows the schematic of a typical dilution tunnel used for particulate sampling from diesel engines. The engine exhaust was sampled through a sampling probe inserted into the main exhaust stream. The exhaust was then directed into a dilution tunnel, where the hot exhaust was mixed with a stream of pressurized, particle free, dry air in two stages using. In the first stage, the exhaust was transferred into the primary dilution tunnel, where the hot exhaust was mixed with a stream of pressurized particle free dry air preheated to a tempera‐ ture of close to the temperature of the exhaust, to avoid particle nucleation, condensation, etc. The primary dilution tunnel was also heated to a temperature close to engine exhaust

nian coagulation and it is very insignificant when compared to other mechanisms.

^ *<sup>p</sup> <sup>ε</sup><sup>k</sup>* / <sup>120</sup>*v* and found that *τts* for turbulent

A two stage dilution is adopted, firstly to prevent rapid dilution, a dilution is not achieved instantaneously but gradually and secondly, to dilute the exhaust in two different environ‐ ments to reduce nucleation/condensation. In the primary dilution tunnel, since the exhaust is mixed with pre-heated air, time required for condensation is high comparable to the resi‐ dence time of the exhaust in dilution tunnel (1~2 sec). In the secondary dilution tunnel, since a small sample from the already diluted exhaust is drawn, the available surface area for con‐ densation is reduced by many times thus condensation is avoided in both stages of dilution.

### **2.2. Particulate mass concentration**

Biodiesel (BD) and blends of ultra low sulfur diesel (ULSD) – BD had a significant effect on particulate emissions. Studies were conducted extensively on PM mass emissions from en‐ gine fueled with BD. Although some authors have reported an increase in PM emissions rel‐ ative to diesel (Durbin et al., 2000; Munack et al., 2001; Alfuso et al., 1993), a large number of studies have confirmed a noticeable decrease in particulate mass while using BD (Lapeurta et al., 2008). However, the reported reductions varied very much depending upon engine conditions, experimental set up, fuel used, engine fuel system and other factors. Several studies reported reductions in the range of around 40 to 50% (Krahl et al., 1996, Lapeurta et al., 2002; Bagley et al., 1998). However, reductions as high as 70 to 90% were also reported by few studies (Canakci and Van Gerpen, 2001; Camden Australia 2005; Kado, 2003; Kalli‐ geros et al., 2003). PM2.5 (AED ≤ 2.5 μm) concentrations for ULSD and WCOB blends were reported by Betha and Balasubramanian, 2011a. They observed that with an increase in per‐ centage of biodiesel in the fuel mixture, particle mass was reduced for B50, and for WCOB (B100) for all loading conditions of engine. For a particular fuel blend, the PM mass in‐ creased with load. Lapuerta et al. (2008) reported that many previous studies observed PM reductions in the range of 40-70% when biodiesel was used. The percentage reduction of PM2.5 reported by Betha and Balasubramanian, 2011a (~35% at full load) was slightly lower than the range reported by Lapuerta et al. (2008). This is mainly because most of the studies, as reported by Lapuerta et al. (2008) in their review paper, compared biodiesel to conven‐ tional low sulfur diesel (sulfur content < 500 ppm) whereas in the study conducted by Betha an Balasubramanian 2011a the comparison of PM2.5 emissions was made with ULSD (sulfur content < 15 ppm). The reduction in PM emissions when using BD can be attributed to the following reasons: (1) the absence of aromatics (Knothe et al., 2006), which are considered as soot precursors, in biodiesel reduces the amount of PM formed during combustion; (2) the higher oxygen content in BD tends to enhance the combustion process resulting in lower particulate emissions; and (3) Finally, the presence of unsaturated fatty acids in BD leads to more complete combustion processes. Unsaturated fatty acids have lower boiling points than diesel, and they can evaporate faster in the combustion chamber than diesel (Song and Zhang, 2008). In addition, the higher viscosity and density of BD compared to ULSD can lead to an increase in the injection pressure. Likewise, higher bulk modulus of compressibili‐ ty of vegetable oils and their methyl esters can lead to advanced injection timing (Boehman et al., 2004) while using BD. As a result, the BD fuel enters the combustion chamber relative‐ ly quicker compared to ULSD (Lapuerta et al., (2008). This advancement in combustion process while using BD increases the residence time of soot particles in the combustion chamber, and thus they undergo further oxidation (Cardone et al., 2002) leading to reduc‐ tion in PM emissions.

health effects (Oberdiester et al., 2001, Nel, 2005) significantly raised a serious concern to develop new ambient standards in terms of particle number rather than mass (Burtscher, 2004). Therefore, particulate number concentrations and size distributions are increasingly studied in comparative studies of particulate emissions from diesel and BD (Kittelson, 1998; Lapeurta et al., 2008; Zhu et al., 2010, Di et al., 2009a and 2009b; Di et al., 2008; Burtscher, 2004). In the literature, both an increase and decrease in the total particle num‐ ber concentrations were reported when using BD. Di et al. (2009b) observed that the total particle number increased 1.5 – 2.5 times when using WCOB compared to diesel depend‐ ing on the engine load. Similar increments (1.35 – 2.4 times) were observed by them in an‐ other study using a direct injection diesel engine. On the other hand, Lapuerta et al. (2007) tested two differently stressed WCOB and observed a reduction (~3 times) in total particle number concentrations (PNC) compared to diesel. Although both of them used WCO in their study, contradictory trends were reported. Studies on other types of BD have also reported contradictory results. A summary of PNC of ULSD and WCOB emis‐ sions during different engine operating conditions is provided in Table 1 (Betha et al., 2011a) and their size distributions are shown in Figure 2 (Betha et al., 2011a). In contrast to PM mass emissions, PNC decreased with an increase in load for all the fuels (shown in Table 1). At higher WCOB-ULSD blend ratios, the percentage decrease in PNC with in‐ creasing load was relatively small compared to ULSD. For ULSD, total PNC decreased by 26% at full load when compared to idle, or no load conditions whereas, for biodiesel, it

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

471

**Total particle number concentration(# cm-3 ) Engine Load (%) ULSD B20 B50 B100** 0 1.14 x 107 1.05 x 107 9.57 x 106 8.98 x 106 30% 9.82 x 106 8.99 x 106 9.19 x 106 8.58 x 106 70% 9.00 x 106 8.91 x 106 8.87 x 106 8.40 x 106 100% 8.46 x 106 8.34 x 106 8.31 x 106 8.15 x 106

**Table 1.** Total PNC for ULSD and WCOB (B100) blends at various loads (Betha et al., 2011a)

It is expected that in diesel engines, particle counts would increase with an increase in load. However, a decrease in PNC with increasing load was observed in this study. Chung et al. (2008) also observed a reduction in PNC at higher loads in their study using a Yanmar backup generator similar to the one used in this study. This observed decrease in PNC was prob‐ ably due to the transfer of particles from nucleation to accumulation or coarser mode at higher loads. It was observed that at higher loads, nucleation mode particles which contrib‐ ute to a major fraction of total number decreased and accumulation mode particles in‐ creased. As a result, there was an overall decrease in total PNC. This shift in particles from the nucleation mode to the accumulation mode was evident from the PSD shown in Figure 2

decreased by only around 9%.

(Betha et al., 2011a).

#### **2.3. Particle number concentrations and size distributions**

New engine designs and emission control devices reduced particulate mass emission dras‐ tically allowing the engines to operate below the emission level standards. However, the concerns about UFPs and nanoparticles (AED < 50 nm) which can contribute to human health effects (Oberdiester et al., 2001, Nel, 2005) significantly raised a serious concern to develop new ambient standards in terms of particle number rather than mass (Burtscher, 2004). Therefore, particulate number concentrations and size distributions are increasingly studied in comparative studies of particulate emissions from diesel and BD (Kittelson, 1998; Lapeurta et al., 2008; Zhu et al., 2010, Di et al., 2009a and 2009b; Di et al., 2008; Burtscher, 2004). In the literature, both an increase and decrease in the total particle num‐ ber concentrations were reported when using BD. Di et al. (2009b) observed that the total particle number increased 1.5 – 2.5 times when using WCOB compared to diesel depend‐ ing on the engine load. Similar increments (1.35 – 2.4 times) were observed by them in an‐ other study using a direct injection diesel engine. On the other hand, Lapuerta et al. (2007) tested two differently stressed WCOB and observed a reduction (~3 times) in total particle number concentrations (PNC) compared to diesel. Although both of them used WCO in their study, contradictory trends were reported. Studies on other types of BD have also reported contradictory results. A summary of PNC of ULSD and WCOB emis‐ sions during different engine operating conditions is provided in Table 1 (Betha et al., 2011a) and their size distributions are shown in Figure 2 (Betha et al., 2011a). In contrast to PM mass emissions, PNC decreased with an increase in load for all the fuels (shown in Table 1). At higher WCOB-ULSD blend ratios, the percentage decrease in PNC with in‐ creasing load was relatively small compared to ULSD. For ULSD, total PNC decreased by 26% at full load when compared to idle, or no load conditions whereas, for biodiesel, it decreased by only around 9%.

**2.2. Particulate mass concentration**

470 Biodiesel - Feedstocks, Production and Applications

tion in PM emissions.

**2.3. Particle number concentrations and size distributions**

New engine designs and emission control devices reduced particulate mass emission dras‐ tically allowing the engines to operate below the emission level standards. However, the concerns about UFPs and nanoparticles (AED < 50 nm) which can contribute to human

Biodiesel (BD) and blends of ultra low sulfur diesel (ULSD) – BD had a significant effect on particulate emissions. Studies were conducted extensively on PM mass emissions from en‐ gine fueled with BD. Although some authors have reported an increase in PM emissions rel‐ ative to diesel (Durbin et al., 2000; Munack et al., 2001; Alfuso et al., 1993), a large number of studies have confirmed a noticeable decrease in particulate mass while using BD (Lapeurta et al., 2008). However, the reported reductions varied very much depending upon engine conditions, experimental set up, fuel used, engine fuel system and other factors. Several studies reported reductions in the range of around 40 to 50% (Krahl et al., 1996, Lapeurta et al., 2002; Bagley et al., 1998). However, reductions as high as 70 to 90% were also reported by few studies (Canakci and Van Gerpen, 2001; Camden Australia 2005; Kado, 2003; Kalli‐ geros et al., 2003). PM2.5 (AED ≤ 2.5 μm) concentrations for ULSD and WCOB blends were reported by Betha and Balasubramanian, 2011a. They observed that with an increase in per‐ centage of biodiesel in the fuel mixture, particle mass was reduced for B50, and for WCOB (B100) for all loading conditions of engine. For a particular fuel blend, the PM mass in‐ creased with load. Lapuerta et al. (2008) reported that many previous studies observed PM reductions in the range of 40-70% when biodiesel was used. The percentage reduction of PM2.5 reported by Betha and Balasubramanian, 2011a (~35% at full load) was slightly lower than the range reported by Lapuerta et al. (2008). This is mainly because most of the studies, as reported by Lapuerta et al. (2008) in their review paper, compared biodiesel to conven‐ tional low sulfur diesel (sulfur content < 500 ppm) whereas in the study conducted by Betha an Balasubramanian 2011a the comparison of PM2.5 emissions was made with ULSD (sulfur content < 15 ppm). The reduction in PM emissions when using BD can be attributed to the following reasons: (1) the absence of aromatics (Knothe et al., 2006), which are considered as soot precursors, in biodiesel reduces the amount of PM formed during combustion; (2) the higher oxygen content in BD tends to enhance the combustion process resulting in lower particulate emissions; and (3) Finally, the presence of unsaturated fatty acids in BD leads to more complete combustion processes. Unsaturated fatty acids have lower boiling points than diesel, and they can evaporate faster in the combustion chamber than diesel (Song and Zhang, 2008). In addition, the higher viscosity and density of BD compared to ULSD can lead to an increase in the injection pressure. Likewise, higher bulk modulus of compressibili‐ ty of vegetable oils and their methyl esters can lead to advanced injection timing (Boehman et al., 2004) while using BD. As a result, the BD fuel enters the combustion chamber relative‐ ly quicker compared to ULSD (Lapuerta et al., (2008). This advancement in combustion process while using BD increases the residence time of soot particles in the combustion chamber, and thus they undergo further oxidation (Cardone et al., 2002) leading to reduc‐


**Table 1.** Total PNC for ULSD and WCOB (B100) blends at various loads (Betha et al., 2011a)

It is expected that in diesel engines, particle counts would increase with an increase in load. However, a decrease in PNC with increasing load was observed in this study. Chung et al. (2008) also observed a reduction in PNC at higher loads in their study using a Yanmar backup generator similar to the one used in this study. This observed decrease in PNC was prob‐ ably due to the transfer of particles from nucleation to accumulation or coarser mode at higher loads. It was observed that at higher loads, nucleation mode particles which contrib‐ ute to a major fraction of total number decreased and accumulation mode particles in‐ creased. As a result, there was an overall decrease in total PNC. This shift in particles from the nucleation mode to the accumulation mode was evident from the PSD shown in Figure 2 (Betha et al., 2011a).

From the PSD shown in Figure 2, it can be observed that with the increase in load, particle peak diameters increased for all fuels. The magnitude of the increase in particle peak diame‐ ters at higher loads was greater for the ULSD than the biodiesel. For ULSD, the peak diame‐ ter increased from 52.3 nm at idle mode to 93 nm at full load and for biodiesel (B100) peak diameter increased from 34 nm at idle to 52.3 nm at full load. However, in their study on particle emissions from stationary diesel engines, Di et al.(2010) and Zhu et al. (2010) report‐ ed an increase in total PNC when engine load was increased. Although there is no definitive explanation for the difference in particle emission trends observed by the above-mentioned studies and trends shown in Figure 2 as well as the study by Chung et al. (2008), a possible reason can be the differences in engine capacities and operating conditions. Both Di et al. (2010) and Zhu et al. (2010) conducted their studies on diesel engines which had much larg‐ er capacity and power (~4000 cc and 88 kW). However, the stationary diesel generator used for the the shown results (Table 2 and Figure 2) (296 cc and 4.5 kW) and the one used by

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

473

The relative number percentage of nucleation (diameter < 50 nm), accumulation (50-100 nm) and fine particles (diameter > 100 nm) emitted from diesel and biodiesel (B100) fuels at vari‐ ous loads is shown in Figure 3. Biodiesel had relatively a higher fraction of nucleation mode particles ranging from 55% to 70 % at different loads when compared to diesel (35% – 60%). A decrease in the nuclei mode particles (diameter < 50 nm) and an increase in accumulation and fine particles (diameter > 100 nm) were observed with an increase in load for both the fuels. For the stationary engine running with ULSD at full load, nucleation (32%), accumula‐ tion (40%) and fine particles (28%) shared almost a similar fraction of particles to the total PNC. However, for BD, nucleation (51%) and accumulation mode particles (43%) were ma‐ jor contributors to the total number concentrations. The fraction of accumulation mode par‐ ticles increased from 30% during idle mode to 40% at full load in the case of ULSD, and a similar increase was observed for biodiesel as well (from 30% at idle mode to 43% at full load). This observation implies that diesel engines emit more accumulation particles at high‐ er loads. At higher loads, more fuel is injected into the combustion chamber to generate ad‐ ditional torque needed and also the residence time for the particles in the combustion chamber decreases relatively. Therefore, the oxidation of particulate soot tends to be re‐ duced, leading to the release of a large fraction of accumulation and fine particles. In the case of biodiesel, the inherent oxygen in the fuel improves the oxidation of soot. Therefore,

Since diesel engines are one of the most significant air pollutant sources in urban areas (Cass, 1998), chemical composition of diesel exhaust has been widely investigated. The chemical pro‐ file of PM plays a crucial role in health and environmental impacts. Variations in the chemical composition of aerosols alter their hygroscopicity and can lead to changes in the cloud-active fraction of the aerosols, or cloud condensation nuclei (CCN) number concentration (Ward et al., 2010). Some carcinogenic and toxic chemical compounds present in DEP when biologically

Chung et al. (2008) (4.8 kW) have lower capacity and power.

the percentage increase of fine particles is relatively less for BD.

**3. Chemical properties of particulate emissions**

**Figure 2.** Particle size distributions of emissions at different loads for ULSD, B50, WCOB (B100) (Betha et al., 2011a)

From the PSD shown in Figure 2, it can be observed that with the increase in load, particle peak diameters increased for all fuels. The magnitude of the increase in particle peak diame‐ ters at higher loads was greater for the ULSD than the biodiesel. For ULSD, the peak diame‐ ter increased from 52.3 nm at idle mode to 93 nm at full load and for biodiesel (B100) peak diameter increased from 34 nm at idle to 52.3 nm at full load. However, in their study on particle emissions from stationary diesel engines, Di et al.(2010) and Zhu et al. (2010) report‐ ed an increase in total PNC when engine load was increased. Although there is no definitive explanation for the difference in particle emission trends observed by the above-mentioned studies and trends shown in Figure 2 as well as the study by Chung et al. (2008), a possible reason can be the differences in engine capacities and operating conditions. Both Di et al. (2010) and Zhu et al. (2010) conducted their studies on diesel engines which had much larg‐ er capacity and power (~4000 cc and 88 kW). However, the stationary diesel generator used for the the shown results (Table 2 and Figure 2) (296 cc and 4.5 kW) and the one used by Chung et al. (2008) (4.8 kW) have lower capacity and power.

The relative number percentage of nucleation (diameter < 50 nm), accumulation (50-100 nm) and fine particles (diameter > 100 nm) emitted from diesel and biodiesel (B100) fuels at vari‐ ous loads is shown in Figure 3. Biodiesel had relatively a higher fraction of nucleation mode particles ranging from 55% to 70 % at different loads when compared to diesel (35% – 60%). A decrease in the nuclei mode particles (diameter < 50 nm) and an increase in accumulation and fine particles (diameter > 100 nm) were observed with an increase in load for both the fuels. For the stationary engine running with ULSD at full load, nucleation (32%), accumula‐ tion (40%) and fine particles (28%) shared almost a similar fraction of particles to the total PNC. However, for BD, nucleation (51%) and accumulation mode particles (43%) were ma‐ jor contributors to the total number concentrations. The fraction of accumulation mode par‐ ticles increased from 30% during idle mode to 40% at full load in the case of ULSD, and a similar increase was observed for biodiesel as well (from 30% at idle mode to 43% at full load). This observation implies that diesel engines emit more accumulation particles at high‐ er loads. At higher loads, more fuel is injected into the combustion chamber to generate ad‐ ditional torque needed and also the residence time for the particles in the combustion chamber decreases relatively. Therefore, the oxidation of particulate soot tends to be re‐ duced, leading to the release of a large fraction of accumulation and fine particles. In the case of biodiesel, the inherent oxygen in the fuel improves the oxidation of soot. Therefore, the percentage increase of fine particles is relatively less for BD.

### **3. Chemical properties of particulate emissions**

**Figure 2.** Particle size distributions of emissions at different loads for ULSD, B50, WCOB (B100) (Betha et al., 2011a)

472 Biodiesel - Feedstocks, Production and Applications

Since diesel engines are one of the most significant air pollutant sources in urban areas (Cass, 1998), chemical composition of diesel exhaust has been widely investigated. The chemical pro‐ file of PM plays a crucial role in health and environmental impacts. Variations in the chemical composition of aerosols alter their hygroscopicity and can lead to changes in the cloud-active fraction of the aerosols, or cloud condensation nuclei (CCN) number concentration (Ward et al., 2010). Some carcinogenic and toxic chemical compounds present in DEP when biologically available can affect human health. Diesel engine emissions consist of a wide range of organic and inorganic compounds in gaseous as well as particulate phases (Bünger et al., 2006). Con‐ centrations of most particle-bound chemical constituents depend on the type of engine, engine load, fuel and lubrication oil properties (Dwivedi et al., 2006). Large surface area of DEP ena‐ bles adsorption of organics and inorganic compounds from the combustion process and/or the adsorption of additional compounds during transport in the ambient air. DEP consists mainly of elemental carbon (EC) (75%), organic carbon (OC) (19%) and small amounts of sulfates, ni‐ trates (1%) and metals & Elements (4%) (Figure 4) (EPA, 2002a).

**Figure 4.** Typical chemical compositions for diesel particulate matter (PM2.5) (EPA, 2002a)

Particulate-bound organic compounds, especially PAHs, are highly carcinogenic. PAHs and their derivatives (nitro-PAHs) together comprise less than 1% of the mass of DEP (EPA, 2002a). The emissions of these compounds are comprehensively studied for diesel engines fuelled with diesel and BD (Jung et al., 2006; Bagley et al., 1998; Correa et al., 2006; Karavala‐ kis et al., 2009; Turro-Baldassari et al., 2004; Zou and Atkinson, 2008; Karavalakis et al., 2010). A majority of studies have found a significant decrease in PAHs emissions with BD compared to that with diesel (Bagley et al., 1998; Correa et al., 2006; Karavalakis et al., 2009). However, a couple of studies have indicated only statistically insignificant reduction in PAHs (Turro-Baldassari et al., 2004; Zou and Atkinson, 2008) when BD is used. The reduc‐ tion in PAH emission may be attributed to the presence of excess oxygen in BD and the ab‐ sence of aromatic and polycyclic aromatic compounds in the fuel. One study (Karavalakis et al., 2010) was found in literature reporting higher PAHs emissions when using BD. Karava‐ lakis et al. (2010) tested BD made from soybean oil and used frying oil. They found lower PAH emissions with BD made from soybean oil. However, BD made from used frying oil emitted more PAH compounds compared to those from diesel. They attributed the increase in PAHs to dimers, trimers, polymerization products, and cyclic acids present in the biodie‐

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

475

Studies on particulate-bound metals emitted from BD combustion are not as comprehensive as PAHs, despite a strong correlation between human health risk and particulate-bound

**3.1. Particle-bound polycyclic aromatic hydrocarbons (PAHs)**

sel made from used frying oil.

**3.2. Particulate-bound elements and trace metals**

**Figure 3.** Fractionation of particle emitted from ULSD WCOB (B100) for various loads (Betha et al., 2011a).

**Figure 4.** Typical chemical compositions for diesel particulate matter (PM2.5) (EPA, 2002a)

### **3.1. Particle-bound polycyclic aromatic hydrocarbons (PAHs)**

available can affect human health. Diesel engine emissions consist of a wide range of organic and inorganic compounds in gaseous as well as particulate phases (Bünger et al., 2006). Con‐ centrations of most particle-bound chemical constituents depend on the type of engine, engine load, fuel and lubrication oil properties (Dwivedi et al., 2006). Large surface area of DEP ena‐ bles adsorption of organics and inorganic compounds from the combustion process and/or the adsorption of additional compounds during transport in the ambient air. DEP consists mainly of elemental carbon (EC) (75%), organic carbon (OC) (19%) and small amounts of sulfates, ni‐

**Figure 3.** Fractionation of particle emitted from ULSD WCOB (B100) for various loads (Betha et al., 2011a).

trates (1%) and metals & Elements (4%) (Figure 4) (EPA, 2002a).

474 Biodiesel - Feedstocks, Production and Applications

Particulate-bound organic compounds, especially PAHs, are highly carcinogenic. PAHs and their derivatives (nitro-PAHs) together comprise less than 1% of the mass of DEP (EPA, 2002a). The emissions of these compounds are comprehensively studied for diesel engines fuelled with diesel and BD (Jung et al., 2006; Bagley et al., 1998; Correa et al., 2006; Karavala‐ kis et al., 2009; Turro-Baldassari et al., 2004; Zou and Atkinson, 2008; Karavalakis et al., 2010). A majority of studies have found a significant decrease in PAHs emissions with BD compared to that with diesel (Bagley et al., 1998; Correa et al., 2006; Karavalakis et al., 2009). However, a couple of studies have indicated only statistically insignificant reduction in PAHs (Turro-Baldassari et al., 2004; Zou and Atkinson, 2008) when BD is used. The reduc‐ tion in PAH emission may be attributed to the presence of excess oxygen in BD and the ab‐ sence of aromatic and polycyclic aromatic compounds in the fuel. One study (Karavalakis et al., 2010) was found in literature reporting higher PAHs emissions when using BD. Karava‐ lakis et al. (2010) tested BD made from soybean oil and used frying oil. They found lower PAH emissions with BD made from soybean oil. However, BD made from used frying oil emitted more PAH compounds compared to those from diesel. They attributed the increase in PAHs to dimers, trimers, polymerization products, and cyclic acids present in the biodie‐ sel made from used frying oil.

### **3.2. Particulate-bound elements and trace metals**

Studies on particulate-bound metals emitted from BD combustion are not as comprehensive as PAHs, despite a strong correlation between human health risk and particulate-bound

metals (Hu et al., 2008; Verma et al., 2010). Very few studies (Dwivedi et al., 2006; Cheung et al., 2011) were found in literature investigating particulate-bound metals in BD. Dwivedi et al. (2006) conducted a comparative assessment and characterization of particulate-bound trace elemental emissions from diesel and rice bran oil derived BD. Elements such as Cr, Ni, Pb, Cd, Na, Al, Mg, and Fe were investigated. The authors observed that concentration of metals such as Cr, Fe, Al, Zn, Mg increased while others (Pb, Cd, Na, Ni) were reduced with the usage of B20 (20% BD). Cheung et al. (2011) also observed higher concentrations of Fe, Zn, Mg when using BD. However, Cr, Al, Pb, Cd, Na, Ni were lower in BD emission com‐ pared to diesel. In both the studies, the particulate-bound elemental concentrations were mainly attributed to the fuel and lubricating oil composition apart from engine wear. Metals and elements that were found higher in fuel were also found higher in the emissions. Since the particulate-bound elements largely depend on fuel quality and composition apart from engine wear, their concentration in the exhaust is expected to vary with feedstock of BD. In another study Betha et al. (2011b) investigated the particulate bound elements from WCOB (B100), ULSD and their blend (B50). They observed that particulate emissions were reduced with the usage of WCOB. However, most of the elements which are known to be toxic such as Zn, Cr, Ni were very high in the WCOB exhaust compared to ULSD. Elements such as As, Co, Al, Mn were found to be in higher levels in ULSD. Elements such as Cr, Cu, Fe, Ba, Zn, Mg, Ni, and K were found in higher concentrations in B100 compared to ULSD. Similar findings were reported by Dwivedi et al. (2006). They found that concentrations of Zn, Fe, and Cr were higher in biodiesel compared to those in diesel. The higher concentrations of elements, especially Cu, Fe, Zn, in B100 used in this study can be attributed to the raw mate‐ rial from which biodiesel was prepared. BD used in this study was derived from WCO gen‐ erated in restaurants and food courts. The oil has been used for cooking and frying of various food products. Elements such as Cu, Fe, Zn and Mn were found in vegetables, (Ka‐ washima and Soares, 2003) Cu, Fe, and Zn in meat (Lombardi-Boccia et al., 2005) and Cu, Zn and Cd in fish (Atta et al., 1997). These elements might have been released into the oil dur‐ ing cooking and therefore, the concentrations of Fe, Zn, Cu, Mn in BD were found to be sig‐ nificantly high. In addition, these elements can also be leached out from the cooking utensils due to heating (Kuligowski and Halperin, 1992).

Exposure assessment –This involves estimation of chronic daily intake (CDI) of these ele‐

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

where C is concentration of pollutant and E is deposition fraction of particles by size given

2

where Dp is the diameter of particles. In this study, PM2.5 (Aerodynamic diameter ≤ 2.5 μm) was used i.e. Dp is 2.5 μm. IR is typically assumed to be 20 m3 day-1 and BW to be 70 kg for

(3) Dose-response assessment- It is the probability of health effects according to the dose of pollutant of concern. Assuming only inhalation as the major exposure route, the reference dose (RfD, mg kg-1, day-1) for toxic elements that are non-carcinogenic was calculated from

ments the inhalation slope factor (SF, mg-1 kg day) was calculated from inhalation unit risk

(4) Risk characterization or estimation of health risk - was calculated based on the exposure and dose–response assessments. For non-carcinogenic metals, it is indicated by (United

For carcinogenic metals, total carcinogenic risk is estimated in terms of excess life time can‐

The human health risk assessment was carried out to quantify the risk associated with the particulate-bound metals emitted from ULSD and WCOB at full load from a stationary en‐

The pertinent information of the TD and RfD, HQ, inhalation SF and ELCR for adults and children are shown in Tables 2 and 3. The concentrations of metals used for this illustration

adults. As for children, the IR and BW are assumed to be 10 m3

) provided by USEPA.

cer risk (ELCR) given by: (United States Department of Energy, 1999).


p p E = -0.081 + 0.23ln (D ) + 0.23 sqrt (D ) (9)

1 1 Total dose (TD,mg m ) x inhalation rate (IR, m day ) CDI(mg kg day ) Body weight (BW,kg)


TD = C x E (8)

) provided by USEPA. Likewise, for carcinogenic ele‐

Hazard Quotient HQ = CDI/RfD ( ) (10)

ELCR = CDI x SF (11)

day-1 and 15 kg, respectively.

http://dx.doi.org/10.5772/53476

477

ments calculated from the following equations.

by (Volckens and Leith, 2003),

reference concentrations (RfC, mg/m3

States Department of Energy, 1999):

values (IUR, mg-1 m3

gine for illustration.

### **4. Estimation of health risk due to particulate emissions**

Human health risk assessment was conducted based on the mean concentrations of particu‐ late-bound elements determined through the experimental study. Health risk assessment is especially useful in understanding the health hazard associated with inhalation exposure to PM emitted from B100 compared to that of ULSD. The details and steps involved in health risk assessment are described in detail elsewhere (See and Balasubramanian, 2006). Briefly, it involves four important steps (NRC, 1983) as described below.

Hazard identification – elements which have known toxicity values are considered. Al, Cr, and Mn induce non-carcinogenic effects while As, Cd, Cr, Ni and Co induce carcinogenic health effects.

Exposure assessment –This involves estimation of chronic daily intake (CDI) of these ele‐ ments calculated from the following equations.

metals (Hu et al., 2008; Verma et al., 2010). Very few studies (Dwivedi et al., 2006; Cheung et al., 2011) were found in literature investigating particulate-bound metals in BD. Dwivedi et al. (2006) conducted a comparative assessment and characterization of particulate-bound trace elemental emissions from diesel and rice bran oil derived BD. Elements such as Cr, Ni, Pb, Cd, Na, Al, Mg, and Fe were investigated. The authors observed that concentration of metals such as Cr, Fe, Al, Zn, Mg increased while others (Pb, Cd, Na, Ni) were reduced with the usage of B20 (20% BD). Cheung et al. (2011) also observed higher concentrations of Fe, Zn, Mg when using BD. However, Cr, Al, Pb, Cd, Na, Ni were lower in BD emission com‐ pared to diesel. In both the studies, the particulate-bound elemental concentrations were mainly attributed to the fuel and lubricating oil composition apart from engine wear. Metals and elements that were found higher in fuel were also found higher in the emissions. Since the particulate-bound elements largely depend on fuel quality and composition apart from engine wear, their concentration in the exhaust is expected to vary with feedstock of BD. In another study Betha et al. (2011b) investigated the particulate bound elements from WCOB (B100), ULSD and their blend (B50). They observed that particulate emissions were reduced with the usage of WCOB. However, most of the elements which are known to be toxic such as Zn, Cr, Ni were very high in the WCOB exhaust compared to ULSD. Elements such as As, Co, Al, Mn were found to be in higher levels in ULSD. Elements such as Cr, Cu, Fe, Ba, Zn, Mg, Ni, and K were found in higher concentrations in B100 compared to ULSD. Similar findings were reported by Dwivedi et al. (2006). They found that concentrations of Zn, Fe, and Cr were higher in biodiesel compared to those in diesel. The higher concentrations of elements, especially Cu, Fe, Zn, in B100 used in this study can be attributed to the raw mate‐ rial from which biodiesel was prepared. BD used in this study was derived from WCO gen‐ erated in restaurants and food courts. The oil has been used for cooking and frying of various food products. Elements such as Cu, Fe, Zn and Mn were found in vegetables, (Ka‐ washima and Soares, 2003) Cu, Fe, and Zn in meat (Lombardi-Boccia et al., 2005) and Cu, Zn and Cd in fish (Atta et al., 1997). These elements might have been released into the oil dur‐ ing cooking and therefore, the concentrations of Fe, Zn, Cu, Mn in BD were found to be sig‐ nificantly high. In addition, these elements can also be leached out from the cooking utensils

due to heating (Kuligowski and Halperin, 1992).

476 Biodiesel - Feedstocks, Production and Applications

health effects.

**4. Estimation of health risk due to particulate emissions**

it involves four important steps (NRC, 1983) as described below.

Human health risk assessment was conducted based on the mean concentrations of particu‐ late-bound elements determined through the experimental study. Health risk assessment is especially useful in understanding the health hazard associated with inhalation exposure to PM emitted from B100 compared to that of ULSD. The details and steps involved in health risk assessment are described in detail elsewhere (See and Balasubramanian, 2006). Briefly,

Hazard identification – elements which have known toxicity values are considered. Al, Cr, and Mn induce non-carcinogenic effects while As, Cd, Cr, Ni and Co induce carcinogenic

$$\text{CDI(mg kg}^{-1}\text{day}^{-1}) = \frac{\text{Total dose (TD/mg m}^3\text{)} \times \text{inhalation rate (IR, m}^3\text{ day}^{-1})}{\text{Body weight (BW/kg)}} \tag{7}$$

$$\text{TD} = \text{C} \times \text{E} \tag{8}$$

where C is concentration of pollutant and E is deposition fraction of particles by size given by (Volckens and Leith, 2003),

$$\mathbf{E} = \text{-0.081} + \text{0.23ln (D\_p)}^2 + \text{0.23 sqrt (D\_p)}\tag{9}$$

where Dp is the diameter of particles. In this study, PM2.5 (Aerodynamic diameter ≤ 2.5 μm) was used i.e. Dp is 2.5 μm. IR is typically assumed to be 20 m3 day-1 and BW to be 70 kg for adults. As for children, the IR and BW are assumed to be 10 m3 day-1 and 15 kg, respectively.

(3) Dose-response assessment- It is the probability of health effects according to the dose of pollutant of concern. Assuming only inhalation as the major exposure route, the reference dose (RfD, mg kg-1, day-1) for toxic elements that are non-carcinogenic was calculated from reference concentrations (RfC, mg/m3 ) provided by USEPA. Likewise, for carcinogenic ele‐ ments the inhalation slope factor (SF, mg-1 kg day) was calculated from inhalation unit risk values (IUR, mg-1 m3 ) provided by USEPA.

(4) Risk characterization or estimation of health risk - was calculated based on the exposure and dose–response assessments. For non-carcinogenic metals, it is indicated by (United States Department of Energy, 1999):

$$\text{Hazzard Quotient } \left( \text{HQ} \right) = \text{CDI/RfD} \tag{10}$$

For carcinogenic metals, total carcinogenic risk is estimated in terms of excess life time can‐ cer risk (ELCR) given by: (United States Department of Energy, 1999).

$$\text{ELCR} = \text{CDI} \times \text{SF} \tag{11}$$

The human health risk assessment was carried out to quantify the risk associated with the particulate-bound metals emitted from ULSD and WCOB at full load from a stationary en‐ gine for illustration.

The pertinent information of the TD and RfD, HQ, inhalation SF and ELCR for adults and children are shown in Tables 2 and 3. The concentrations of metals used for this illustration are adopted from Betha et al. (2011b) (shown in Table 4) and CDI is calculated using Eqns (7) – (9). The concentrations reported in Betha et al., 2011b represent those emitted from the raw engine exhaust. However, in reality the engine exhaust is diluted by ambient air once it is released to the atmosphere. The dilution factor is typically 1000 times when exhaust is re‐ leased to the ambient atmosphere on road conditions (Zielinska, 2005). The mean concentra‐ tions of elements were divided by 1000 to be used in health risk calculations. The deposition efficiency E for particle with 2.5 μm is nearly 0.70. The CDI is calculated by first estimating the TD of the each element (Tables 2 and 3).

**ULSD**

**Metals**

**WCOB**

**Metals**

Non carcinogenic metals

Carcinogenic metals

WCOB and ULSD (Betha et al., 2011b)

cancer after exposure to PM2.5 by B100 fuel.

Non carcinogenic metals

Carcinogenic metals

**CDI**

**CDI**

**(mg kg-1day-1)**

Al 1.50 x 10-5 1.43 x 10-3 1.05 x 10-2 Cr 5.09 x 10-6 2.86 x 10-5 1.78 x 10-1 Mn 8.98 x 10-8 1.43 x 10-5 6.28 x 10-3

**(mg kg-1day-1)**

Al 2.30 x 10-5 1.43 x 10-3 1.61 x 10-2 Cr 2.85 x 10-6 2.86 x 10-5 9.95 x 10-2 Mn 2.14 x 10-7 1.43 x 10-5 1.50 x 10-2

**RfD**

**RfD**

**(mg kg-1day-1) HQ**

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

As 5.85 x 10-8 15.1 8.84 x 10-7 Cd 8.85 x 10-9 6.3 5.58 x 10-8 Cr 2.85 x 10-6 4.2 1.20 x 10-5 Ni 1.87 x 10-7 84 1.57 x 10-5

**(mg kg-1day-1) HQ**

As 2.23 x 10-8 15.1 3.37 x 10-7 Cd 5.38 x 10-9 6.3 3.39 x 10-8 Cr 5.09 x 10-6 4.2 2.14 x 10-5 Ni 2.04 x 10-7 84 1.71 x 10-5

**Table 3.** Estimation of human health risk in children due to particulate bound elements from PM2.5 emitted from

As shown in Tables 2 and 3, the levels of non-carcinogenic risk (total HQ) were estimated to be 0.06 for ULSD and 0.08 for WCOB and carcinogenic risk (total ELCR) to be 12.3 x 10-6 for ULSD and 16.6 x 10-6 for WCOB for adults. In the case of children, non-carcinogenic and car‐ cinogenic risks for both the fuels are higher than those in adults. Total HQ was estimated to be 0.13 for ULSD and 0.2 for B100, while total ELCR was 28.6 x 10-6 for ULSD and 38.8 x 10-6 for WCOB. It implies that 28 to 29 children or 12 to 13 adults in a million can get cancer after exposure to the toxic trace metals in PM2.5 emitted from the combustion of ULSD. In the case of biodiesel, it is even higher, 38 to 39 children or 16 to 17 adults out of a million can get

**SF**

**(mg kg-1day)**

∑= 1.31 x 10-2 ∑ = 28.6 x 10-6

**(mg kg-1day)**

∑ = 1.95 x 10-1 ∑ = 38.8 x 10-6

**SF**

**ELCR**

http://dx.doi.org/10.5772/53476

479

**ELCR**


**Table 2.** Estimation of human health risk in adults due to particulate bound elements from PM2.5 emitted from WCOB and ULSD (Betha et al., 2011b)

are adopted from Betha et al. (2011b) (shown in Table 4) and CDI is calculated using Eqns (7) – (9). The concentrations reported in Betha et al., 2011b represent those emitted from the raw engine exhaust. However, in reality the engine exhaust is diluted by ambient air once it is released to the atmosphere. The dilution factor is typically 1000 times when exhaust is re‐ leased to the ambient atmosphere on road conditions (Zielinska, 2005). The mean concentra‐ tions of elements were divided by 1000 to be used in health risk calculations. The deposition efficiency E for particle with 2.5 μm is nearly 0.70. The CDI is calculated by first estimating

the TD of the each element (Tables 2 and 3).

478 Biodiesel - Feedstocks, Production and Applications

**CDI**

**CDI**

**(mg kg-1 day-1)**

Al 6.42 x 10-6 1.43 x 10-3 4.49 x 10-3 Cr 2.18 x 10-6 2.86 x 10-5 7.63 x 10-2 Mn 3.85 x 10-8 1.43 x 10-5 2.69 x 10-3

**(mg kg-1 day-1)**

Al 9.84 x 10-6 1.43 x 10-3 6.88 x 10-3 Cr 1.22 x 10-6 2.86 x 10-5 4.26 x 10-2 Mn 9.18 x 10-8 1.43 x 10-5 6.42 x 10-3

**RfD**

**RfD**

**(mg kg-1 day-1) HQ**

As 2.51 x 10-8 15.1 3.79 x 10-7 Cd 3.79 x 10-9 6.3 2.39 x 10-8 Cr 1.22 x 10-6 4.2 5.12 x 10-6 Ni 8.02 x 10-8 84 6.74 x 10-6

**(mg kg-1 day-1) HQ**

As 9.57 x 10-9 15.1 1.45 x 10-7 Cd 2.31 x 10-9 6.3 1.45 x 10-8 Cr 2.18 x 10-6 4.2 9.16 x 10-6 Ni 8.72 x 10-8 84 7.33 x 10-6

**Table 2.** Estimation of human health risk in adults due to particulate bound elements from PM2.5 emitted from WCOB

**SF**

**(mg kg-1 day)**

∑=5.59 x10-2 ∑ =12.3 x10-6

**(mg kg-1 day)**

∑=8.34x 10-2 ∑=16.6 x 10-6

**SF**

**ELCR**

**ELCR**

**ULSD**

**Metals**

**WCOB**

**Metals**

Non carcinogenic metals

Carcinogenic metals

and ULSD (Betha et al., 2011b)

Non carcinogenic metals

Carcinogenic metals


**Table 3.** Estimation of human health risk in children due to particulate bound elements from PM2.5 emitted from WCOB and ULSD (Betha et al., 2011b)

As shown in Tables 2 and 3, the levels of non-carcinogenic risk (total HQ) were estimated to be 0.06 for ULSD and 0.08 for WCOB and carcinogenic risk (total ELCR) to be 12.3 x 10-6 for ULSD and 16.6 x 10-6 for WCOB for adults. In the case of children, non-carcinogenic and car‐ cinogenic risks for both the fuels are higher than those in adults. Total HQ was estimated to be 0.13 for ULSD and 0.2 for B100, while total ELCR was 28.6 x 10-6 for ULSD and 38.8 x 10-6 for WCOB. It implies that 28 to 29 children or 12 to 13 adults in a million can get cancer after exposure to the toxic trace metals in PM2.5 emitted from the combustion of ULSD. In the case of biodiesel, it is even higher, 38 to 39 children or 16 to 17 adults out of a million can get cancer after exposure to PM2.5 by B100 fuel.


**5. Summary**

**Author details**

University of Singapore, Singapore

2 National Tsing Hua University, Taiwan

per.DOI: 10.4271/1999-01-1142

, Rajasekhar Balasubramanian1

Raghu Betha1

**References**

1999-2008.

Particle. physical and chemical properties play a key role in determining the health effects associated with PM emissions. Smaller particles can penetrate deep inside the alveolar re‐ gions of lungs. Bio-available particulate-bound compounds pose serious health problems. WCOB had lower PNC compared to that of ULSD. However, WCOB had a higher fraction of nucleation mode particles relative to that of ULSD, and therefore, a large fraction of PM emitted from WCOB can deposit in respiratory system compared to DPM. Unlike other types of biodiesel WCOB has higher metal concentrations both in the fuel as well as particu‐ late emissions because of the nature of feedstock. Metals are leached into the oil during cooking and also from cooking utensils. Health risk inhalation of PM was calculated by as‐ sessing the CDI estimated using the concentration of particulate-bound compounds and the deposition efficiency of PM in human body, which indicates that WCOB has higher health risk compared to ULSD in terms of particulate bound elements. However, when PAHs are also taken into consideration it can either increase or decrease the relative health risk of WCOB particles depending on the PAHs emission concentrations from both the fuels.

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

481

and Guenter Engling2

1 Department of Civil and Environmental Engineering, Faculty of Engineering, National

[1] Abdul-Khalek, I., Kittelson, D.B., Brear, F., 1999. The Influence of Dilution Condition on Diesel Exhaust Particle Size Distribution Measurements. SAE Technical Pa‐

[2] Alfuso S., Auriemma, M., Police, G., Prati M. V., 1993. The effect of methyl ester of rapeseed oil on combustion and emissions of DI engines, SAE Paper, 932801.

[4] Atadashi, I.M., Aroua, M.K., Abdul, A.A., 2010. High quality biodiesel and its diesel engine application: A review. Renewable and Sustainable Energy Reviews, 14,

[5] Atta, M.B., Elsebaie, E.A., Noaman, M.A., Kassab, H.E., 1997. The effect of cooking on the content of heavy metals in fish (Tilapia nilotica). Food Chemistry 58, 1-4.

[3] ASTM-D-975, 2006. Standard specification for diesel fuel oils, ASTM.

**Table 4.** Concentration of particulate bound elements in raw exhaust of a stationary engine

From the results it can be deduced that the non-carcinogenic risk indicated by HQ was high‐ er for WCOB compared to ULSD for both groups of people. However, for both ULSD and WCOB, the total HQ was very low for adults compared to children and for both the groups total HQ was below acceptable levels, (Acceptable levels for total HQ =1). On the other hand carcinogenic risk indicated by ELCR was found to be much higher than the acceptable limit for both groups and for both fuels (i.e., 1 in a million) and that ELCR for WCOB was greater than ULSD. From the risk assessment results made in this study, it appears that exposure to PM2.5 emitted from biodiesel poses higher risk when compared to PM2.5 emitted from ULSD. However, it is to be noted that in this study the carcinogenic risk due to particulate bound elements was used as a measure to evaluate the total carcinogenic risk. A more comprehen‐ sive and extensive research needs to be done to evaluate the complete risk assessment in‐ cluding many other carcinogenic compounds such as PAHs and nitro-PAHs. Studies have shown that PAH emissions from biodiesel are very much lower compared to diesel (Jalava et al., 2010; Karavalakis et al., 2011; Lin et al., 2011; Turrio-Baldassarri et al., 2004). Therefore, the total carcinogenic risk of WCOB exhaust particles might be actually lower than ULSD.

In the case of PAHs the the risk assessment for PAHs that are probable and possible human carcinogens were calculated using petency equivalency factor (PEF) relative to BaP and the CDI calculated from Eq (7). Table 5 shows the PAHs with know PEFs (Collins et al., 1998).


**Table 5.** Classification of PAHs by IARC and Potency equivalency factor (PEF)

Carcinogenic risk due to individual PAHs is calculated as product of CDI and PEF. The total carcinogenic risk is the summation of individual risk.

### **5. Summary**

**Element ULSD (mg/m3) WCOB(mg/m3)**

From the results it can be deduced that the non-carcinogenic risk indicated by HQ was high‐ er for WCOB compared to ULSD for both groups of people. However, for both ULSD and WCOB, the total HQ was very low for adults compared to children and for both the groups total HQ was below acceptable levels, (Acceptable levels for total HQ =1). On the other hand carcinogenic risk indicated by ELCR was found to be much higher than the acceptable limit for both groups and for both fuels (i.e., 1 in a million) and that ELCR for WCOB was greater than ULSD. From the risk assessment results made in this study, it appears that exposure to PM2.5 emitted from biodiesel poses higher risk when compared to PM2.5 emitted from ULSD. However, it is to be noted that in this study the carcinogenic risk due to particulate bound elements was used as a measure to evaluate the total carcinogenic risk. A more comprehen‐ sive and extensive research needs to be done to evaluate the complete risk assessment in‐ cluding many other carcinogenic compounds such as PAHs and nitro-PAHs. Studies have shown that PAH emissions from biodiesel are very much lower compared to diesel (Jalava et al., 2010; Karavalakis et al., 2011; Lin et al., 2011; Turrio-Baldassarri et al., 2004). Therefore, the total carcinogenic risk of WCOB exhaust particles might be actually lower than ULSD.

In the case of PAHs the the risk assessment for PAHs that are probable and possible human carcinogens were calculated using petency equivalency factor (PEF) relative to BaP and the CDI calculated from Eq (7). Table 5 shows the PAHs with know PEFs (Collins et al., 1998).

2A: Probable Human Carcinogen 2B: Possible Human Carcinogen

Carcinogenic risk due to individual PAHs is calculated as product of CDI and PEF. The total

**PAH Group PEF** Benz(a)anthracene, BaA 2A 0.1 Benz(a)pyrene, BaP 2A 1 Benzo(b)fluoranthene, BbF 2B 0.1 Benzo(k)fluoranthene, BkF 2B 0.01 Indeno(1,2,3-cd)pyrene, Ind 2B 0.1

**Table 5.** Classification of PAHs by IARC and Potency equivalency factor (PEF)

carcinogenic risk is the summation of individual risk.

Al 147.6 96.3 Mn 1.4 0.6 Cr 18.3 32.7 Ni 1.2 1.3 Cd 0.06 0.03 As 0.4 0.14

480 Biodiesel - Feedstocks, Production and Applications

**Table 4.** Concentration of particulate bound elements in raw exhaust of a stationary engine

Particle. physical and chemical properties play a key role in determining the health effects associated with PM emissions. Smaller particles can penetrate deep inside the alveolar re‐ gions of lungs. Bio-available particulate-bound compounds pose serious health problems. WCOB had lower PNC compared to that of ULSD. However, WCOB had a higher fraction of nucleation mode particles relative to that of ULSD, and therefore, a large fraction of PM emitted from WCOB can deposit in respiratory system compared to DPM. Unlike other types of biodiesel WCOB has higher metal concentrations both in the fuel as well as particu‐ late emissions because of the nature of feedstock. Metals are leached into the oil during cooking and also from cooking utensils. Health risk inhalation of PM was calculated by as‐ sessing the CDI estimated using the concentration of particulate-bound compounds and the deposition efficiency of PM in human body, which indicates that WCOB has higher health risk compared to ULSD in terms of particulate bound elements. However, when PAHs are also taken into consideration it can either increase or decrease the relative health risk of WCOB particles depending on the PAHs emission concentrations from both the fuels.

### **Author details**

Raghu Betha1 , Rajasekhar Balasubramanian1 and Guenter Engling2

1 Department of Civil and Environmental Engineering, Faculty of Engineering, National University of Singapore, Singapore

2 National Tsing Hua University, Taiwan

### **References**


[6] Bagley, S.T., Gratz, L.D., Johnson, J.H., McDonald, J.F., 1998. Effects of an oxidation catalytic converter and a biodiesel fuel on the chemical, mutagenic,andparticle size characteristics of emissions from a diesel engine. Environmental Science and Tech‐ nology, 32, 1183–1191.

[19] Collins, J.F., Brown, J.P., Alexeeff, G.V., Salmon, A.G, 1998. Potency equivalency fac‐ tors for some polycyclic aromatic hydrocarbons and polycyclic aromatic hydrocar‐

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

483

[20] Correa, S.M., Arbilla, G.., 2006. Aromatichydrocarbonsemissions in diesel and biodie‐

[21] CRC, 2002. CRC PM Workshop Summary. CRC Workshop on Vehicle Exhaust Parti‐ cle Emissions Measurement Methodology, Manchester Grand Hyatt Hotel, San Die‐

[22] Demirbas, A., 2008. Biodiesel: a realistic fuel alternative for diesel engines. London,

[23] Di, Y., Cheung, C.S., Huang, Z., 2008. Experimental investigation on regulated and unregulated emissions of a diesel engine fueled with ultra-low sulfur diesel fuel blended with biodiesel from waste cooking oil. Science of the Total Environment,

[24] Di, Y., Cheung, C.S., Huang, Z. 2009a. Experimental investigation of particulate emis‐ sions from a diesel engine fueled with ultralow-sulfur diesel fuel blended with di‐

[25] Di , Y., Cheung, C.S., Huang, Z. 2009b. Comparison of the Effect of Biodiesel-Diesel and Ethanol-Diesel on the Particulate Emissions of a Direct Injection Diesel Engine.

[26] Di, Y., Cheung, C.S., Huang, Z.H., 2010. Experimental investigation of particulate emissions from a diesel engine fueled with ultralow-sulfur diesel fuel blended with

[27] Donaldson, K., Stone, V., Gilmour, P.V., Brown, D.M., MacNee, W., 2000. Ultrafine particles: mechanisms of lung injury. Philosophical Transactions of The Royal Society of London Series A-Mathematical Physical and Engineering Sciences, 58, 2741-2750.

[28] Durbin T., Norbeck J. M., 2000. Effects of biodiesel, biodiesel blends, and a synthetic diesel on emissions from light and heavy-duty diesel vehicles. Environmental Sci‐

[29] Durbin, T.D., Cocker, D.R., Sawant, A.A., Johnson, K., Miller, J.W., Holden, B.B., Hel‐ geson, N.L., Jack, J.A., 2007. Regulated emissions from biodiesel fuels from on/off-

[30] Dwivedi, D., Agarwal, A.K., Sharma, M., 2006. Particulate emission characterization of a biodiesel vs diesel-fuelled compression ignition transport engine: A comparative

[31] EN-590, 2004. Autmotive fuels - diesel -requirements and test methods, UNE

road applications. Atmospheric Environment 41, 5647-5658.

study. Atmospheric Environment, 40, 5586-5595.

bon derivatives. Regulatory Toxicology and Pharmacology, 28(1), 45-54.

sel exhaust. Atmospheric Environment, 40, 6821–6826.

glyme. Atmospheric Environment, 44, 55-63.

Aerosol Science and Technology, 43, 455-465.

diglyme. Atmospheric Environment, 44, 55-63.

ence and Technology, 34, 349-355.

go, California.

407, 835-846.

United Kingdom: Springer


[19] Collins, J.F., Brown, J.P., Alexeeff, G.V., Salmon, A.G, 1998. Potency equivalency fac‐ tors for some polycyclic aromatic hydrocarbons and polycyclic aromatic hydrocar‐ bon derivatives. Regulatory Toxicology and Pharmacology, 28(1), 45-54.

[6] Bagley, S.T., Gratz, L.D., Johnson, J.H., McDonald, J.F., 1998. Effects of an oxidation catalytic converter and a biodiesel fuel on the chemical, mutagenic,andparticle size characteristics of emissions from a diesel engine. Environmental Science and Tech‐

[7] Betha, R., Balasubramanian, R., 2011a. A study of particulate emissions from a sta‐ tionary engine fuelled with ultra-low sulfur diesel blended with waste cooking oilderived biodiesel. Journal of Air and Waste management association, 61, 1063-1069.

[8] Betha R., Balasubramanian R., 2011b. Particulate emissions from stationary engine: Characterization and risk assessment. Atmospheric Environment. 45, 5273 – 5281.

[9] Boehman, L.A., Morris, D., Szybist, J., 2004. The impact of bulk modulus of diesel

[10] Bünger, J., Krahl, J., Weigel, A., Schröder, O., Brüning, T., Müller, M., Hallier, E., and Westphal, G., 2006. Influence of fuel properties, nitrogen oxides, and exhaust treat‐ ment by an oxidation catalytic converter on the mutagenicity of diesel engine emis‐

[11] Burtscher, H., 2004, Physical characterization of particulate emissions from diesel en‐

[12] Camden Council (Australia). Camdem Council Biodiesel Truck Trial 2005; Final re‐ port. Available online: www.camden.nsw.gov.au/files/camden\_council\_biodie‐

[13] Canakci, M., Van Gerpen, J.H., 2001. Comparison of engine performance and emis‐ sions for petroleum diesel fuel, yellow grease biodiesel, and soybean oil biodiesel. ASAE Annual international meeting, Sacramento, California, July 28-31, 46, 937-944.

[14] Cardone, M., Prati, M.V., Rocco, V., Seggiani, M., Senatore, A., and Vitolo, S., 2002. Brassica carinata as an alternative oil crop for the production of biodiesel in Italy: En‐ gine performance and regulated and unregulated exhaust emissions. Environmental

[15] Carraretto, C., Macor, A., Mirandola, A., Stoppato, A., Tonon, S., 2004. Biodiesel as alternative fuel: experimental analysis and energetic evaluations. Energy, 29,

[16] Cass, G.R., 1998. Organic molecular tracers for particulate air pollution sources. Trac-

[18] Chung, A., Lall, A.A. Paulson, S.E., 2008. Particulate emissions by a small non-road diesel engine: Biodiesel and diesel characterization and mass measurements using the extended idealized aggregates theory. Atmospheric Environment, 42, 2129-2140.

[17] CFR, 2006. Title 40 Chapter I, part 60 of the Code of Federal Regulations (CFR).

fuels on fuel injection timing. Energy Fuels, 18, 1877-1882.

gines: a review. Journal of Aerosol Science, 36, 896-932.

sions. Archives of Toxicology, 80, 540-546.

sel\_final\_report\_march2005a.pdfS

Science and Technology, 36, 4656-4662.

Trends in Analytical Chemistry, 6, 356-365.

2195-2211.

nology, 32, 1183–1191.

482 Biodiesel - Feedstocks, Production and Applications


[32] EPA, 1999. Analysis of the Impacts of Control Programs on Motor Vehicle Toxics Emissions and Exposure in Urban Areas and Nationwide: Volume 1, EPA420- R-99-029, November 1999

[45] Kado, N.Y., Kuzmicky, P.A., 2003. Bioassay analyses of particulate matter from a die‐ sel bus engine using various biodiesel feedstock fuels. National Renewable Energy

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

485

[46] Kalligeros, S., Zannikos, F., Stournas, S., Lois, E., Anastopoulos, G., Teas, Ch., Sakel‐ lapoulos, F., 2003. An investigation of using biodiesel/marine diesel blends on the performance of a stationary diesel engine. Biomass and Bioenergy, 24, 141-149.

[47] Karavalakis, G., Bakeas, E., Stournas, S., 2010. Influence of Oxidized Biodiesel Blends on Regulated and Unregulated Emissions from a Diesel Passenger Car. Environmen‐

[48] Karavalakis, G., Stournas, S., and Bakeas, E., 2009. Light vehicle regulated and un‐ regulated emissions from different biodiesels. Science of the Total Environment 407,

[49] Kaufmann, T. G., Kaldor, A., 1999. Catalysis science and technology for cleaner trans‐ portation fuels. Workshop on Building the Future of Catalysis, Egmond Zee, Nether‐

[50] Kawashima, L.M., Soares, L.M.V., 2003. Mineral profile of raw and cooked leafy veg‐ etables consumed in Southern Brazil. J. Food Composition and Analysis 16, 605-611.

[51] Kerminen, V.M., Wexler A.S.,1995. The Interdependence of Aerosol Processes and Mixing in Point-Source Plumes. Atmospheric Environment 29(3): 361-375.

[52] Kittelson, D.B., Johnson,J. H., 1991. Variability of Particle Emission Measurements in

[53] Kittelson, D.B., 1998. Engines and nanoparticles: A review. Journal of Aerosol Sci‐

[54] Kittelson D.B., Watts, W.F. Johnson, J.P., 2003. Nanoparticle emissions on Minnesota

[55] Knothe, G., Sharp, C.A., Ryan, T.W., 2006. Exhaust emissions of biodiesel, petrodie‐ sel, neat methyl esters, and alkanes in a new technology engine. Energy & Fuels, 20,

[56] Korhonen, P., Kulmala, M., Laaksonen, A., Viisanen, Y., McGraw, R., Seinfeld, J.H., 1999. Ternary nucleation of H2SO4, NH3, and H2O in the atmosphere. Journal of Ge‐

[57] Krahl, J., Munack, A., Bahadir, M., Schumacher, L., Elser, N., 1996. Review: utiliza‐ tion of rapeseed oil, rapeseed oil methyl ester or diesel fuel: exhaust gas emissions

[58] Kuligowski, J., Halperin, K.M., 1992. Stainless-Steel Cookware as a Significant Source of Nickel, Chromium, and Iron. Archives of Environmental Contamination and Toxi‐

the Heavy Duty Transient Test. SAE Paper 42: 137-162

highways. Atmospheric Environment, 38, 9 – 19.

ophysical Research-Atmospheres 104(D21): 26349-26353.

and estimation of environmental effects. SAE paper, 962096.

Laboratory 2003 NREL/SR-510-31463.

tal Science and Technology, 44, 5306-5312.

3338-3346.

lands, Elsevier Science Bv.

ence. 29, 575-588.

cology, 23, 211-215.

403-408.


[45] Kado, N.Y., Kuzmicky, P.A., 2003. Bioassay analyses of particulate matter from a die‐ sel bus engine using various biodiesel feedstock fuels. National Renewable Energy Laboratory 2003 NREL/SR-510-31463.

[32] EPA, 1999. Analysis of the Impacts of Control Programs on Motor Vehicle Toxics Emissions and Exposure in Urban Areas and Nationwide: Volume 1, EPA420-

[33] EPA, 2002. Health Assessment Document for Diesel Exhaust: Office of Research and

[34] Fazal, M.A., Haseeb A.S.M.A., Masjuki, H.H., 2011. Biodiesel feasibility study: An evaluation of material compatibility; performance; emission and engine durability.

[35] Ferella, F., Di Celso, G.M., De Michelis, I., Stanisci, V., Veglio, F., 2010. Optimization

[36] Giracol, J., Passarini, K.C., da Silva, S.C., Calarge, F.A., Tambourgi, E.B., Santana, J.C.C., 2011. Reduction In Ecological Cost Through Biofuel Production From Cooking Oils: An Ecological Solution For The City Of Campinas, Brazil. Journal of Cleaner

[37] Guerrassi, N., Dupraz P., 1998. A common rail injection system for high speed direct

[38] Gunvachai K., Hassan, M.G., Shama, G., Hellgardt, K., 2007. A New Solubility Model to Describe Biodiesel Formation Kinetics. Process Safety and Environmental Protec‐

[39] Hansen, J., Sato,M., Reudy, R., Lacis, A., Oinas, V., 2000. Global warming in the twenty-first century: An alternative scenario." Proceedings of the National Academy

[40] Hildemann, L.M., Cass, G.R.,Markowski, J.R., 1989. A Dilution Stack Sampler for Collection of Organic Aerosol Emissions - Design, Characterization and Field-Tests.

[41] Holmen, B. A., Ayala A., 2002. Ultrafine PM emissions from natural gas, oxidationcatalyst diesel, and particle-trap diesel heavy-duty transit buses. Environmental Sci‐

[42] Hu, S., Polidori, A., Arhami, M., Shafer, M.M., Schauer, J.J., Cho, A., Sioutas, C., 2008. Redox activity and chemical speciation of size fractioned PM in the communities of the Los Angeles-Long Beach harbor. Atmospheric Chemistry and Physics, 8,

[43] Janaun, J., Ellis, N., Perspectives on biodiesel as a sustainable fuel. Renewable and

[44] Jung, H., Kittelson, D.B., Zachariah, M.R., 2006. Characteristics of SME biodiesel-fu‐ eled diesel particle emissions and the kinetics of oxidation. Environmental Science

of the transesterification reaction in biodiesel production. Fuel, 89, 36-42.

injection diesel engines. SAE Technical paper.DOI: 10.4271/980803

of Sciences of the United States of America 97(18): 9875-9880.

Aerosol Science and Technology 10(1): 193-204.

ence & Technology 36(23): 5041-5050.

Sustainable Energy Reviews, 14, 1312-1320.

and Technology, 40, 4949–4955.

Renewable and Sustainable Energy Reviews,15, 1314-1324.

R-99-029, November 1999

484 Biodiesel - Feedstocks, Production and Applications

Development, Sept.2002.

Production, 19, 1324-1329.

tion, 85, 383-389.

6439-6451.


[59] Kulmala, M.,Laaksonen, A., 1990. Binary Nucleation of Water Sulfuric-Acid System - Comparison of Classical-Theories with Different H2so4 Saturation Vapor-Pressures. Journal of Chemical Physics 93(1): 696-701.

[73] Song J.T., Zhang, C.H., 2008. An experimental study on the performance and exhaust emissions of a diesel engine fuelled with soybean oil methyl ester. IMechE, 222,

Physico-Chemical Characteristics of Particulate Emissions from Diesel Engines Fuelled with Waste Cooking Oil…

http://dx.doi.org/10.5772/53476

487

[74] Stamatelos, A. M., 1997. A review of the effect of particulate traps on the efficiency of

[75] Su, D.S., Muller, J.O., Jentoff, R.E., Rothe, D., Jacob, E., Schlogl, R., 2004. Fullerenelike soot from EuroIV diesel engine: consequences for catalytic automotive pollution

[76] Sydbom, A., Blomberg, A.,Parnia, S., Stenfors, N., Sandstorm, T., Dahlen, S.E., 2001. Health effects of diesel exhaust emissions. European Respiratory Journal 17(4):

[77] Szulczyk K.R., McCarl, B. A., 2010. Market penetration of biodiesel. Renewable and

[78] Turrio-Baldassarri, L., Battistelli, C. L., Conti, L., Crebelli, R., De Berardis, B., Iamice‐ li, A.L., Gambino, M., Iannaccone, S., 2004. Emission comparison of urban bus engine fuelled with diesel oil and biodiesel blend. Science Total Environment, 327, 147-162.

[79] United States Department of Energy (US DOE), 1999. Guidance for Conducting Risk Assessments and Related Risk Activities for the DOE-ORO Environmental Manage‐

[80] Verma, V., Shafer, M. M., Schauer, J. J., Sioutas, C., 2010. Contribution of transition metals in the reactive oxygen species activity of PM emissions from retrofitted

[81] Volckens, J., Leith, D., 2003. Partitioning theory for respiratory deposition of semivo‐

[82] Ward, D.S., Eidhammer, T., Cotton, W.R., Kreidenweis. 2010. The role of the particle size distribution in assessing aerosol composition effects on simulated droplet activa‐

[83] Xue, J., Grift, T.E., Hansen, A.C., 2011. Effect of biodiesel on engine performances and emissions. Renewable and Sustainable Energy Reviews, 15, 1098-1116.

[84] Zhang, K. M.,Wexler,A. S., 2002. A hypothesis for growth of fresh atmospheric nu‐

[85] Zhang, K.M., Wexler,A. S., 2004. Evolution of particle number distribution near road‐ ways - Part I: analysis of aerosol dynamics and its implications for engine emission

[86] Zhu, L., Zhang, W.G., Liu, W., Huang, Z., 2010. Experimental study on particulate and NOx emissions of a diesel engine fueled with ultra low sulfur diesel, RME-diesel blends and PME-diesel blends. Science of the Total Environment 408, 1050-1058.

heavy-duty vehicles. Atmospheric Environment 44, 5165-5173.

latile aerosols. Annals of Occupational Hygiene 47, 157-164.

tion. Atmospheric chemistry and Physics, 10, 5435-5447.

clei. Journal of Geophysical Research-Atmospheres 107(D21).

measurement. Atmospheric Environment 38(38): 6643-6653.

vehicle diesel engines. Energy Conversion and Management 38(1): 83-99.

control. Topics in Catalysis, 30/31, 241-245.

Sustainable Energy Reviews, 14, 2426-2433.

ment Program. BJC/OR-271.

2487-2495.

733-746.


[73] Song J.T., Zhang, C.H., 2008. An experimental study on the performance and exhaust emissions of a diesel engine fuelled with soybean oil methyl ester. IMechE, 222, 2487-2495.

[59] Kulmala, M.,Laaksonen, A., 1990. Binary Nucleation of Water Sulfuric-Acid System - Comparison of Classical-Theories with Different H2so4 Saturation Vapor-Pressures.

[60] Lapuerta, M., Rodriguez-Fernandez, J., Agudelo, J.R., 2007. Diesel particulate emis‐ sions from used cooking oil biodiesel. Bioresource Technology, 99, 731-740.

[61] Lapuerta, M., Armas, O., Rodriguez-Fernandez, J., 2008. Effect of biodiesel fuels on diesel engine emissions. Progress in Energy and Combustion Science 34, 198-223.

[62] Lin, Y. C., Hsu, K.H., and Chen, C.B., 2011a. Experimental investigation of the per‐ formance and emissions of a heavy-duty diesel engine fueled with waste cooking oil

[63] Lombardi-Boccia, G., Lanzi, S., Aguzzi, A., 2005. Aspects of meat quality: trace ele‐ ments and B vitamins in raw and cooked meats. Journal of Food Composition and

[64] Meng, X.M., Chen G.Y., Wang, Y.H., 2008. Biodiesel production from waste cooking oil via alkali catalyst and its engine test. Fuel Processing Technology, 89, 851-857.

[65] Mercer-Blackman, V., Samiei, H., Cheng, K., 2007. Biofuel Demand Pushes Up Food Prices.Available: http://www.imf.org/external/pubs/ft/survey/so/2007/RES1017A.htm

[66] Munack A., Schroder, O., Krahl, J., Bunger, J., 2001. Comparison of relevant gas emii‐ sions from biodiesel and fossil diesel fuel. Agricultural engineering International: the CIGR Journal of Scientific Research and Development; III; Manuscirpt EE 01 001.

[67] NRC, 1983. Risk Assessment in the Federal Government: Managing the Process. Na‐ tional Research Council. Committee on the Institutional Means for Assessment of

[68] Oberdorster, G., 2001. Pulmonary effects of inhaled ultrafine particles. International

[69] Pahl, G., 2008. Biodiesel—Growing a new energy economy, 2 ed. White River Junc‐

[70] Park, C., Kook, S., Bae, C., 2004. Effects of multiple injections in a HSDI engine equip‐ ped with common rail injection system. SAE Technical paper.DOI:

[71] Pischinger, F.F., 1996. The diesel engine for cars - Is there a future? Fall Technical Conference of the ASME Internal Combustion Engine Division, Springfield, Ohio,

[72] See, S.W., Balasubramanian, R., 2006. Risk assessment of exposure to indoor aerosols

associated with chinese cooking. Environment Research, 102, 197-204.

Risks to Public Health. National Academy Press, Washington, DC.

Archives of Occupational and Environmental Health 74(1): 1-8.

tion, Vermont: Chelsea Green Publishing Company.

biodiesel/ultra-low sulfur diesel blends. Energy 36, 241-248.

Journal of Chemical Physics 93(1): 696-701.

Analysis 18, 39-46.

486 Biodiesel - Feedstocks, Production and Applications

10.4271/2004-01-0127

Asme-AmerSoc Mechanical Eng.


[87] Zou, L., Atkinson, S., 2008. Characterizing vehicle emissions from burning of biodie‐ sel made from vegetable oil. Environmental Technology, 24, 1253-1260.

[87] Zou, L., Atkinson, S., 2008. Characterizing vehicle emissions from burning of biodie‐

sel made from vegetable oil. Environmental Technology, 24, 1253-1260.

488 Biodiesel - Feedstocks, Production and Applications

### *Edited by Zhen Fang*

This book focuses on the development of biodiesel systems from the production of feedstocks and their processing technologies to the comprehensive applications of both by-products and biodiesel. It should be of interest for students, researchers, scientists and technologists.

Photo by CHAIWATPHOTOS / iStock

Biodiesel - Feedstocks, Production and Applications

Biodiesel

Feedstocks, Production and Applications