microalgae can grow in a small area with more productivity (Himmel et al. 2007;
Sticklen et al. 2006; Olguin 2012). Hence, microalgae can be considered as an
attractive material for biofuel production. The process of biofuel production using
microalgae has been shown in Fig. 2.5.
Some important features of microalgae are:
1. High productivity in comparison to other biological sources like soybean plant
biomasses.
2. These are non-food-based feedstock resources for biofuel production.
3. Microalgae can be easily cultivated on non-arable land.
4. Microalgae can utilize wastewater and fresh, blackish, marine, and saline water
for their growth.
5. They produce biofuels and other several valuable products.
6. Excellent recycling potential of CO 2 as well as nutrients present in the waste.
Based on the above points, microalgae are considered as a potential option for
biofuel production (Razeghifard et al. 2013). The algal fuel also known as oilgae is
derived from triglycerides (triglycerides synthesized by algal cell and called as algal
oil) [Simionato et al. 2013; Gimpel et al. 2013]. Triglycerides can be converted into
biodiesel by using different processing technologies same as second-generation
biofuels. Biogas can also be produced from algae via anaerobically digestion. This
process is very advantageous due to the elimination of biofuel drying process. The
biomass drying process consumes a large amount of energy and time. The
chemotrophic organisms can cultivate in phototrophic fermenters and obtain energy
in the presence of sunlight. Phototrophic organisms generally cultivate in the closed
photobioreactors as well as open pond system (Anto et al. 2020; Show et al. 2013).
The fermentation tanks are a closed system and need to transfer CO 2 and nutrient
from time to time. The pond is an open system and takes CO 2 from the atmosphere.
CO 2 works as a fertilizer and increases the growth of algae in the pond. The algal
cells make their own food in the presence of sunlight and CO 2 present in the
atmosphere. But laboratory photobioreactors are an artificial system, and a suitable
condition is maintained with the help of CO 2 supply and artificial LED light.
However, a large-scale photobioreactor is placed and directly exposed to sunlight.
The production cost of the pond is significantly lower, but due to contamination
problem, it cannot be used for the growth of single species. The contamination
problem does not appear in the packed photobioreactors. Thereby, it is useful for
single species organisms and applicable at industrial scale. Open ponds are considered as the best place for the growth of extremophiles like halophiles and thermophiles (Karemore et al. 2016; Day et al. 2012).
The production of third-generation biofuels are based on cyanobacteria and
microalgae, but these fuels are not commercially available. The third-generation
biofuel production is under development process and to furthermore investigation in
this sector. Researchers are trying to enhance the production of third-generation
biofuels through various strategies. Some challenges appeared in the thirdgeneration biofuels such as enhancement of the production of biofuel through
several methods (Rogers et al. 2014). Biomass of microalgae and macroalgae can
38
V. Singh et al.
Sticklen et al. 2006; Olguin 2012). Hence, microalgae can be considered as an
attractive material for biofuel production. The process of biofuel production using
microalgae has been shown in Fig. 2.5.
Some important features of microalgae are:
1. High productivity in comparison to other biological sources like soybean plant
biomasses.
2. These are non-food-based feedstock resources for biofuel production.
3. Microalgae can be easily cultivated on non-arable land.
4. Microalgae can utilize wastewater and fresh, blackish, marine, and saline water
for their growth.
5. They produce biofuels and other several valuable products.
6. Excellent recycling potential of CO 2 as well as nutrients present in the waste.
Based on the above points, microalgae are considered as a potential option for
biofuel production (Razeghifard et al. 2013). The algal fuel also known as oilgae is
derived from triglycerides (triglycerides synthesized by algal cell and called as algal
oil) [Simionato et al. 2013; Gimpel et al. 2013]. Triglycerides can be converted into
biodiesel by using different processing technologies same as second-generation
biofuels. Biogas can also be produced from algae via anaerobically digestion. This
process is very advantageous due to the elimination of biofuel drying process. The
biomass drying process consumes a large amount of energy and time. The
chemotrophic organisms can cultivate in phototrophic fermenters and obtain energy
in the presence of sunlight. Phototrophic organisms generally cultivate in the closed
photobioreactors as well as open pond system (Anto et al. 2020; Show et al. 2013).
The fermentation tanks are a closed system and need to transfer CO 2 and nutrient
from time to time. The pond is an open system and takes CO 2 from the atmosphere.
CO 2 works as a fertilizer and increases the growth of algae in the pond. The algal
cells make their own food in the presence of sunlight and CO 2 present in the
atmosphere. But laboratory photobioreactors are an artificial system, and a suitable
condition is maintained with the help of CO 2 supply and artificial LED light.
However, a large-scale photobioreactor is placed and directly exposed to sunlight.
The production cost of the pond is significantly lower, but due to contamination
problem, it cannot be used for the growth of single species. The contamination
problem does not appear in the packed photobioreactors. Thereby, it is useful for
single species organisms and applicable at industrial scale. Open ponds are considered as the best place for the growth of extremophiles like halophiles and thermophiles (Karemore et al. 2016; Day et al. 2012).
The production of third-generation biofuels are based on cyanobacteria and
microalgae, but these fuels are not commercially available. The third-generation
biofuel production is under development process and to furthermore investigation in
this sector. Researchers are trying to enhance the production of third-generation
biofuels through various strategies. Some challenges appeared in the thirdgeneration biofuels such as enhancement of the production of biofuel through
several methods (Rogers et al. 2014). Biomass of microalgae and macroalgae can
38
V. Singh et al.