**6. Biodiesel from algae**

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate changemitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other

significant economic potential because as a non-renewable fuel that fossil fuel prices will increase inescapability further in the future. Finally, biodiesel is better than diesel fuel in

Extraction of oil was carried out using two extraction solvent systems to compare the oil content in each case and select the most suitable solvent system for the highest biodiesel

A known weight of each ground dried algal species (10 g dry weight) was mixed separately with the extraction solvent mixture; chloroform/methanol (100 ml, 2:1, v/v) for 20 min. using shaker, followed by the addition of mixture of chloroform/water (50 ml, 1:1, v/v) for 10 min. filter and the algal residue was extracted three times by 100 ml chloroform followed

A known weight of each ground dried algal species (10 g dry weight) was mixed with the extraction solvent mixture, hexane/ether (100 ml, 1:1, v/v), kept to settle for 24 hrs,

The extracted oil was evaporated under vaccum to release the solvent mixture solutions using rotary evaporator at 40- 45 °C. Then, the oil produced from each algal species was mixed with a mixture of catalyst (0.25g NaOH) and 24 ml methanol, a process called transesterification (Fig. 2, 3,4, 5 and Table 2), with stirring properly for 20 min. The Mixture was kept for 3hrs in electric shaker at 3000 rpm. (National Biodiesel Board, 2002). After shaking the solution was kept for 16 hrs to settle the biodiesel and the sediment layers clearly. The biodiesel layer was separated from sedimentation by flask separator carefully. Quantity of sediments (glycerin, pigments, etc) was measured. Biodiesel (Fig. 6) was washed by 5% water many times until it becomes clear then Biodiesel was dried by using dryer and finally kept under the running fan for 12 h. the produced biodiesel was measured (using

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate changemitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other

terms of flash point and biodegradability [Ma *et al*., 1999].

**5. Algae as potentials for biodiesel production** 

**5.1 Separation of biodiesel from algae** 

**5.1.1.2 Hexane/ether (1:1, v/v) method** 

**6. Biodiesel from algae** 

**5.1.1.1 Chloroform /methanol (2:1, v/v) method** 

by filtration (Fig.1) according to Bligh and Dayer (1959).

**5.1.2 Transesterification and biodiesel production** 

measuring cylinder), pH was recorded and stored for analysis.

followed by filtration (Fig. 1) according to Hossain and Salleh (2008).

**5.1.1 Extraction of oil** 

yield (Afify *et al*., 2010).

available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO2, wastewater treatment, in human health, as food additive, and for aquaculture (Mata *et al*., 2010).

Biodiesel seem to be a viable choice but its most significant drawback is the cost of crop oils, such as canola oil, that accounts for 80% of total operating cost, used to produce biodiesel (Demirbas, 2007). Besides, the availability of the oil crop for the biodiesel production is limited (Chisti, 2008). Therefore, it is necessary to find new feedstock suitable for biodiesel production, which does not drain on the edible vegetable oil supply. One alternative to oil crops is the algae because they contain lipids suitable for esterification/ transesterification. Among many types of algae, microalgae seem to be promising (Table 1) because:



Table 1. Biochemical composition of algae expressed on a dry matter basis (Becker, 1994)

Algae are made up of eukaryotic cells. These are cellswith nuclei and organelles. All algae have plastids, the bodies with chlorophyll that carry out photosynthesis. But the various strains of algae have different combinations of chlorophyll molecules. Some have only Chlorophyll A, some A and B, while other strains, A and C [Benemann *et al*., 1978]. Algae biomass contains three main components: proteins, carbohydrates, and natural oil. The

Algal Biomass and Biodiesel Production 119

Fig. 5 shows a schematic representation of the algal biodiesel value chain stages, starting with the selection of microalgae species depending on local specific conditions and the design and implementation of cultivation system for microalgae growth. Then, it follows the biomass harvesting, processing and oil extraction to supply the biodiesel production

Algae's potential as a feedstock is dramatically growing in the biofuel market. Microalgae (to distinguish it from such macroalgae species as seaweed) have many desirable attributes

unit.

Fig. 5. Microalgae biodiesel value chain stages.





as energy producers [Choe *et al*., 2002]:



chemical compositions of various microalgae are shown in Table 1. While the percentages vary with the type of algae, there are algae types that are comprised of up to 40% of their overall mass by fatty acids [Becker, 1994]. It is this fatty acid (oil) that can be extracted and converted into biodiesel.


Table. 2. Types of transesterification catalysts

Fig. 4. Biodiesel from algae

chemical compositions of various microalgae are shown in Table 1. While the percentages vary with the type of algae, there are algae types that are comprised of up to 40% of their overall mass by fatty acids [Becker, 1994]. It is this fatty acid (oil) that can be extracted and

2-Large scale production 2-The later disposal process is

5-high conversion of the production 5-the waste water pollute the

cheap 3-The process need much energy

complex

recycle

acids

environment

1-reaction temperature is relative high and the process is complex

4-Need a installation for methanol

2-Chemicals arise in the process of production are poisons to enzyme

1-Limitation of enzyme in the conversion of short chain fatty

1-High temperature and high pressure in the reaction condition leads to high coast for production

and waste energy

**Type of transesterification Advantage Disadvantage**

controlled

**Enzymatic catalyst** 1-Moderate reaction condition

Table. 2. Types of transesterification catalysts

1-reaction condition can be well

4-The methanol produced in the

2-The small amount of methanol

3-Have no pollution to natural

process can be recycled

required in the reaction

1-Easy to be controlled

2-It is safe and fast 3-friendly to environment

environment

3-The cost of the production process is

converted into biodiesel.

**Chemical catalysis** 

**Supercritical fluid techniques** 

Fig. 4. Biodiesel from algae

Fig. 5 shows a schematic representation of the algal biodiesel value chain stages, starting with the selection of microalgae species depending on local specific conditions and the design and implementation of cultivation system for microalgae growth. Then, it follows the biomass harvesting, processing and oil extraction to supply the biodiesel production unit.

Fig. 5. Microalgae biodiesel value chain stages.

Algae's potential as a feedstock is dramatically growing in the biofuel market. Microalgae (to distinguish it from such macroalgae species as seaweed) have many desirable attributes as energy producers [Choe *et al*., 2002]:


Algal Biomass and Biodiesel Production 121

1-Most algal lipid have lower fuel

2-The cost of cultivation is higher compared to common crop oil

lipids but complicated lipoid

content are required

crops currently

biodiesel by catalyst

1-Filteration and cultivation of yeasts and mildews with high-

complex and new technology

3-The cost of cultivation is also higher compared to common

1-Conataing a lot of saturated fatty acids which is hard to converted to

value than diesel fuel

currently

**7.2 Disadvantages of biodiesel from algae oil** 


**Microalgal oil** 

**Oleaginous yeast and** 

yeast and waste oils

**mildews** 


vegetable oil

microalgae

nature

**Waste oils** 1-The waste oil is cheap compared to crop oils


**Type of organism Advantage Disadvantage**

3-Short-time growth cycle 4-Composition is relative single in

1-Resource are abundant in the

3-Short time growth cycle

4-Strong capability of growth in different cultivation on conditions

1-Fatty acid profile similar to

2-Under certain condition it may be as high as 85% of the dry weight

**Bacteria oil** 1-Fast growth rate 1-Most of bacteria can not yield

Table 3. Advantage and disadvantage of algae as biodiesel source compared with bacteria,

Quantifying the land use changes associated with intensive biofuel feedstock production relies upon many assumptions [Chisti,. 2007], but it is clear that the accelerated cultivation of terrestrial plant biomass for biofuels will have an exceptionally large land footprint (Table 4). For example, the United States has the fourth largest absolute biodiesel potential of the 119 countries studied by Johnston and Holloway [Johnston, M. and Holloway, 2007]. However, recent work has suggested that the projected year 2016 demand for corn ethanol alone would require 43% of all U.S. land used for corn production in 2004 [Chisti,. 2007]. A related study concluded that the annual corn production needed to satisfy one half of all U.S. transportation fuel needs would require an area equivalent to more than eight times the U.S. land area that is presently used for crop production [Chisti,. 2007]. Other land-based crops would require less cropland, based on their oil content: oil palm (24% of current cropland area), coconut (54%), jatropha (77%), canola (122%) and soybean (326%) [Chisti,. 2007]. Moreover, recent work indicates that the ability of countries to grow terrestrial crops explicitly for the production of biofuels such as ethanol and biodiesel is significantly overestimated [Johnston, M. and Holloway, 2007], contributing to concerns that these biofuels are not feasible options for providing a significant fraction of global fuel demand.

**8. Comparison between biodiesel production from algae and vegetables** 

2-High oil content in some species 2-Process of oils extracted is

