might not extract incomplete, essentially free fatty acids from lipids. This method
sometimes may also remove large amounts of non-saponifiable and non-nutritious
material such as pigments. To address this problem, a range of modern and advanced
methods were implemented by improving existing methods for extracting
microalgae oil bodies. Ramluckana et al. [60], for example, used single, binary,
and more than two organic solvents at a time to extract oil bodies, while
Boutekedjiret et al. [61] proposed the use of green bio-solvents (terpenes) extracted
from aromatic plants. The oil bodies should undergo transesterification for biodiesel
production, and the process comprises of methanolysis or ethanolysis in the fatty
acid methyl esters (FAME) forms. The process of transesterification requires catalysts, which may be acidic or alkaline in nature. Such catalysts have their own pros
and cons. The transesterification of complex lipids and free fatty can be performed
by using acid catalysts, whereas basic catalysts could not be able to esterify free fatty
acids.
Acid catalysts can transesterify both complex lipids and free fatty acids, while
basic catalyst cannot esterify free fatty acids.
The difficulty associated with the usage of acid catalyst is it needs extended
reaction time than a basic catalyst with the additional heating requirement [62]. To
prevail over these hurdles, some complementary approaches are reported. Heaton
et al. [63], for example, utilized both base and acid catalyst along with alcohol.
Carrapiso and Garcıa [62] later used a blend of a base and acid catalyst in methanol.
Initially, algal biomass is wrecked down into its key contents: lipid, carbohydrate,
protein, and remaining mass through extraction/fractionation technology to make
them apt for conversion to bioproducts and biofuels.
The extraction method varies based on the type of product extracted from the
biomass and also on the particular composition of the biomass feedstock. Chemical
conversion techniques like pyrolysis, gasification, anaerobic digestion, liquefaction,
fermentation, and transesterification are normally used to transform algal biomass
into fuels such as ethanol, biodiesel, methane, hydrogen, acetone, charcoal, and
butanol. The transformation of harvested biomass to biofuels and other bioproducts
is one of the main technical challenges, and it is also not cost-effective.
9 Utilization of Wastewater for Microalgae Cultivation
Algae can effectively be grown even on harsh environment (not appropriate for other
purposes) and with wastewater or water not suitable for food production
[64, 65]. The algae are having the ability to grow on non-cultivable land, by using
wastewater; algae could be able to produce large amounts of biofuels (per acre) when
compared to oil-producing plant.
Microalgae have shown great promise in removal of phosphorus and nitrogen
(as these nutrients are recycled), and it can effectively be transformed into algal
biomass at cheap cost through solar energy. Biofuels produced from algae have 50%
less greenhouse emissions than petroleum fuel. By overcoming the economic
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B. Srinivasan and G. Kulshreshtha
sometimes may also remove large amounts of non-saponifiable and non-nutritious
material such as pigments. To address this problem, a range of modern and advanced
methods were implemented by improving existing methods for extracting
microalgae oil bodies. Ramluckana et al. [60], for example, used single, binary,
and more than two organic solvents at a time to extract oil bodies, while
Boutekedjiret et al. [61] proposed the use of green bio-solvents (terpenes) extracted
from aromatic plants. The oil bodies should undergo transesterification for biodiesel
production, and the process comprises of methanolysis or ethanolysis in the fatty
acid methyl esters (FAME) forms. The process of transesterification requires catalysts, which may be acidic or alkaline in nature. Such catalysts have their own pros
and cons. The transesterification of complex lipids and free fatty can be performed
by using acid catalysts, whereas basic catalysts could not be able to esterify free fatty
acids.
Acid catalysts can transesterify both complex lipids and free fatty acids, while
basic catalyst cannot esterify free fatty acids.
The difficulty associated with the usage of acid catalyst is it needs extended
reaction time than a basic catalyst with the additional heating requirement [62]. To
prevail over these hurdles, some complementary approaches are reported. Heaton
et al. [63], for example, utilized both base and acid catalyst along with alcohol.
Carrapiso and Garcıa [62] later used a blend of a base and acid catalyst in methanol.
Initially, algal biomass is wrecked down into its key contents: lipid, carbohydrate,
protein, and remaining mass through extraction/fractionation technology to make
them apt for conversion to bioproducts and biofuels.
The extraction method varies based on the type of product extracted from the
biomass and also on the particular composition of the biomass feedstock. Chemical
conversion techniques like pyrolysis, gasification, anaerobic digestion, liquefaction,
fermentation, and transesterification are normally used to transform algal biomass
into fuels such as ethanol, biodiesel, methane, hydrogen, acetone, charcoal, and
butanol. The transformation of harvested biomass to biofuels and other bioproducts
is one of the main technical challenges, and it is also not cost-effective.
9 Utilization of Wastewater for Microalgae Cultivation
Algae can effectively be grown even on harsh environment (not appropriate for other
purposes) and with wastewater or water not suitable for food production
[64, 65]. The algae are having the ability to grow on non-cultivable land, by using
wastewater; algae could be able to produce large amounts of biofuels (per acre) when
compared to oil-producing plant.
Microalgae have shown great promise in removal of phosphorus and nitrogen
(as these nutrients are recycled), and it can effectively be transformed into algal
biomass at cheap cost through solar energy. Biofuels produced from algae have 50%
less greenhouse emissions than petroleum fuel. By overcoming the economic
152
B. Srinivasan and G. Kulshreshtha