1.3.3 Extraction of Algal Oil
The harvested biomass must be processed for extraction of desired final product.
Methods that have been used include sun drying, low-pressure shelf drying, spray
drying, drum drying, fluidized bed drying, freeze drying, and refractance Window
TM technology drying (Molina et al. 1994; Prakash et al. 1997; Leach et al. 1998;
Desmorieux and Decaen 2006; Nindo and Tang 2007). Sun drying is the cheapest
dehydration method; but it takes long time, and required large drying surfaces with
the risk of material loss (Prakash et al. 1997). Spray drying can be used for oil
extraction but it is relatively expensive and can cause significant deterioration of
some algal pigments commonly (Desmorieux and Decaen 2006). Freeze drying is
also expensive, during large-scale operations, but it eases extraction of oils. Intracellular elements such as oils are difficult to extract from wet biomass with solvents
without cell disruption, but are extracted more easily from freeze dried biomass
(Molina et al. 1994, 2003). A balance between the drying efficiency and cost
effectiveness is important for the extraction of biofuels in order to maximize the
net energy output of the fuels (Li et al. 2008). The cost of drying is also an important
consideration for lipid extraction from microalgae biomass powder for the food and
feed industry (Li et al. 2008). Drying temperature affects the composition and total
yield of lipid from the algal biomass (Widjaja et al. 2009). High concentration of
TAG in the lipids could be retained at 60
C with slight decreases in the lipid yield.
Drying at above 60
C can resulted decrease in both the concentration of TAG and
lipid yield (Widjaja et al. 2009). OriginOil (a biofuel company based in Los Angeles)
has also developed a wet extraction method that combines ultrasound and electromagnetic pulse induction to break the algae cell walls. In this method gaseous carbon
dioxide is added to the algae solution to lower the pH that resulted in easy separation
of biomass from the oil (Heger 2009).
1.4
Algal Biofuel Production Technologies
There are several pathways which are used for biofuel production by using algal
bio-metabolite (bio-oils and residue). First of all, bio-metabolite is produced from
chemically treated algal biomass, after that it is used for biofuel conversion.
1.4.1 Transesterification
It is an alcohol based conversion of fat or oil into esters (fatty acid methyl esters;
FAMEs) and glycerol. There is nothing unique about the transesterification of algal
oil compared with that of conventional vegetable oils. Alcohol such as methanol,
ethanol, propanol, butanol, and amyl alcohol are used in transesterification process,
especially methanol is common in use because of its low cost and its physical and
chemical advantages. Three types of transesterification method (viz. acidic, alkaline,
and enzymatic) can be performed for conversion of oil in its ester form. In alkali
1 Algal Biofuel: A Sustainable Approach for Fuel of Future Generation
11
The harvested biomass must be processed for extraction of desired final product.
Methods that have been used include sun drying, low-pressure shelf drying, spray
drying, drum drying, fluidized bed drying, freeze drying, and refractance Window
TM technology drying (Molina et al. 1994; Prakash et al. 1997; Leach et al. 1998;
Desmorieux and Decaen 2006; Nindo and Tang 2007). Sun drying is the cheapest
dehydration method; but it takes long time, and required large drying surfaces with
the risk of material loss (Prakash et al. 1997). Spray drying can be used for oil
extraction but it is relatively expensive and can cause significant deterioration of
some algal pigments commonly (Desmorieux and Decaen 2006). Freeze drying is
also expensive, during large-scale operations, but it eases extraction of oils. Intracellular elements such as oils are difficult to extract from wet biomass with solvents
without cell disruption, but are extracted more easily from freeze dried biomass
(Molina et al. 1994, 2003). A balance between the drying efficiency and cost
effectiveness is important for the extraction of biofuels in order to maximize the
net energy output of the fuels (Li et al. 2008). The cost of drying is also an important
consideration for lipid extraction from microalgae biomass powder for the food and
feed industry (Li et al. 2008). Drying temperature affects the composition and total
yield of lipid from the algal biomass (Widjaja et al. 2009). High concentration of
TAG in the lipids could be retained at 60
C with slight decreases in the lipid yield.
Drying at above 60
C can resulted decrease in both the concentration of TAG and
lipid yield (Widjaja et al. 2009). OriginOil (a biofuel company based in Los Angeles)
has also developed a wet extraction method that combines ultrasound and electromagnetic pulse induction to break the algae cell walls. In this method gaseous carbon
dioxide is added to the algae solution to lower the pH that resulted in easy separation
of biomass from the oil (Heger 2009).
1.4
Algal Biofuel Production Technologies
There are several pathways which are used for biofuel production by using algal
bio-metabolite (bio-oils and residue). First of all, bio-metabolite is produced from
chemically treated algal biomass, after that it is used for biofuel conversion.
1.4.1 Transesterification
It is an alcohol based conversion of fat or oil into esters (fatty acid methyl esters;
FAMEs) and glycerol. There is nothing unique about the transesterification of algal
oil compared with that of conventional vegetable oils. Alcohol such as methanol,
ethanol, propanol, butanol, and amyl alcohol are used in transesterification process,
especially methanol is common in use because of its low cost and its physical and
chemical advantages. Three types of transesterification method (viz. acidic, alkaline,
and enzymatic) can be performed for conversion of oil in its ester form. In alkali
1 Algal Biofuel: A Sustainable Approach for Fuel of Future Generation
11