reactions are mostly performed using co-solvent and ionic liquids. Co-solvents
increase the efficiency of lipid extraction and increase the overall yield. In one of
the study, hexane was used as the co-solvent and was supplemented with sulfuric
acid and methanol. It was reported that the yield of biodiesel increased from 16.6 to
94.5% with an increase in hexane supplementation from 2 to 10 mL
(Sangaletti-Gerhard et al. 2015). Comparison of chloroform and hexane as
co-solvent established that chloroform increases the yield of biodiesel more than
hexane (Kim et al. 2015). The use of co-solvent not only increases the yield but also
reduces the requirement of methanol, facilitating the downstream processing. It has
been reported in a study that the use of diethyl ether as a co-solvent reduced the
requirement of methanol from 105:1 to 79:1 (Ehimen et al. 2012). Study to evaluate
the transesterification reaction with different co-solvents (petroleum ether, chloroform, n-hexane, ethyl ether, carbon tetrachloride, n-butanol, and acetone) established that the highest ester yields were obtained with use of petroleum ether,
chloroform, and n-hexane. The yield increased from 48.3% to above 90% when a
co-solvent was used with ethanol clearly confirming the role of co-solvent (Zhang
et al. 2015). Research has been also focused toward development of green solvents
which will eliminate the harmful effects of conventional solvents (Jeevan Kumar
et al. 2017). In recent years, the ionic liquids (salts in liquid form) have been
utilized in biodiesel production. Ionic liquids come with advantages like high
solubility, inherent basicity or acidity, negligible vapor pressure, and are recyclable.
They also possess the ability to immobilize the catalysts (acid/basic), and this
makes them easily separable and recyclable. Cost of the ionic liquids is the major
drawback currently restricting their application in biodiesel production process
especially considering the requirement at large scale. There are very few studies
reported on the use of ionic liquids, and more research needs to be carried out for
their application in biodiesel production from microalgae with a focus on reducing
the requirement and maximizing the reuse during the processing.
5.2 Bioethanol
The biofuel which accounts for a significant fraction of the total production is
bioethanol. Majority of it is produced from sugarcane and the remaining comes
from other crops. Bioethanol from biomass is produced via fermentation or gasification process, and the availability of the feedstock depends upon the season and
geographical conditions. Microalgae can be one of the potential feedstock for
bioethanol production as they are able to produce starch and cellulose and also do
not compete with the food crops for land and water. The production of bioethanol
4 Process Intensification of Biofuel Production …
71
increase the efficiency of lipid extraction and increase the overall yield. In one of
the study, hexane was used as the co-solvent and was supplemented with sulfuric
acid and methanol. It was reported that the yield of biodiesel increased from 16.6 to
94.5% with an increase in hexane supplementation from 2 to 10 mL
(Sangaletti-Gerhard et al. 2015). Comparison of chloroform and hexane as
co-solvent established that chloroform increases the yield of biodiesel more than
hexane (Kim et al. 2015). The use of co-solvent not only increases the yield but also
reduces the requirement of methanol, facilitating the downstream processing. It has
been reported in a study that the use of diethyl ether as a co-solvent reduced the
requirement of methanol from 105:1 to 79:1 (Ehimen et al. 2012). Study to evaluate
the transesterification reaction with different co-solvents (petroleum ether, chloroform, n-hexane, ethyl ether, carbon tetrachloride, n-butanol, and acetone) established that the highest ester yields were obtained with use of petroleum ether,
chloroform, and n-hexane. The yield increased from 48.3% to above 90% when a
co-solvent was used with ethanol clearly confirming the role of co-solvent (Zhang
et al. 2015). Research has been also focused toward development of green solvents
which will eliminate the harmful effects of conventional solvents (Jeevan Kumar
et al. 2017). In recent years, the ionic liquids (salts in liquid form) have been
utilized in biodiesel production. Ionic liquids come with advantages like high
solubility, inherent basicity or acidity, negligible vapor pressure, and are recyclable.
They also possess the ability to immobilize the catalysts (acid/basic), and this
makes them easily separable and recyclable. Cost of the ionic liquids is the major
drawback currently restricting their application in biodiesel production process
especially considering the requirement at large scale. There are very few studies
reported on the use of ionic liquids, and more research needs to be carried out for
their application in biodiesel production from microalgae with a focus on reducing
the requirement and maximizing the reuse during the processing.
5.2 Bioethanol
The biofuel which accounts for a significant fraction of the total production is
bioethanol. Majority of it is produced from sugarcane and the remaining comes
from other crops. Bioethanol from biomass is produced via fermentation or gasification process, and the availability of the feedstock depends upon the season and
geographical conditions. Microalgae can be one of the potential feedstock for
bioethanol production as they are able to produce starch and cellulose and also do
not compete with the food crops for land and water. The production of bioethanol
4 Process Intensification of Biofuel Production …
71