7.2.2.2.3 Municipal Solid Wastes
Due to rapid industrialization, there is huge increase in solid wastes (1.3 Â 10
9 ton in
1990 to 2.3 Â 10
9 ton in 2000) generated from different residential and nonresidential establishments. These are usually recyclable biomass generated from food
wastes and paper mill sludge (Hadar 2013). However, the application of these wastes
is limited because of differences in composition and microbial contamination and
limited potential in small regions. These are usually used for bio-oil production using
pyrolysis and solid waste management’s approaches for generation of value-added
organic products.
7.2.3 Third-Generation Feedstock for Bioethanol Production
The algae are simple chlorophyll-containing photosynthetic organisms. These are
either phototrophic, i.e., utilizing atmospheric CO 2 to nutrients such as carbohydrate,
or heterotrophic, i.e., utilizing organic carbon sources (Wen and Chen 2003). Algal
biomass is considered as an alternative to 1G and 2G feedstock due to high
productivity, easy cultivation techniques, can use waste water for cultivation, and
convenient harvesting. The algal biomass serves three major purposes, i.e.,
bioethanol production (algal polysaccharides), biodiesel production (algal
bio-oils), and simultaneous waste water treatment. Microalgae and macroalgae are
two major groups of algae and have huge potential for bioethanol production.
7.2.3.1 Microalgae as Feedstock for Bioethanol Production
Microalgae consist of unicellular prokaryotic or eukaryotic photosynthetic
microorganisms. They have simple colony structures and are capable of surviving
under stressed condition (Mata et al. 2010). The total global production of dry algal
biomass is 10,000 ton/year, of which around 7000 ton/year is produced in open
systems (Gris et al. 2013; Lee and Lee 2016). Different species of microalgae used
for production of bioethanol are Chlorella, Spirulina, and Dunaliella. The major
polysaccharide yields are arabinose, galactose, glucose, rhamnose, and xylose with
bioethanol yield potential of 0.234 g/g dry algal biomass having high 11.7 g/L titer
(Ho et al. 2013). Microalgae can also be used for generation of bio-butanol, acetone,
biogas (Marin et al. 2018), eicosapentaenoic acid (Cheng-Wu et al. 2001), omega-3
oil, livestock feed (Besada et al. 2009), pharmaceuticals, and cosmetics (Spolaore
et al. 2006). These sub-products are of high value and thus can facilitate in
minimizing the cost of the overall bioethanol production process (Demirbas 2011).
The chemical composition of the microalgae is affected extensively by the cultivation type and cultivation condition (Burton et al. 2009).
7.2.3.2 Macroalgae as Feedstock for Bioethanol Production
Seaweed or macroalgae have in-habituated to marine form during the course of
evolution. They are broadly classified as Rhodophyceae (red algae), Phaeophyceae
(brown algae), and Chlorophyceae (green algae) based on the type of pigments they
produce (Jung et al. 2013). Major species of red algae are Eucheuma sp. Eucheuma
166
B. Kumar et al.
Due to rapid industrialization, there is huge increase in solid wastes (1.3 Â 10
9 ton in
1990 to 2.3 Â 10
9 ton in 2000) generated from different residential and nonresidential establishments. These are usually recyclable biomass generated from food
wastes and paper mill sludge (Hadar 2013). However, the application of these wastes
is limited because of differences in composition and microbial contamination and
limited potential in small regions. These are usually used for bio-oil production using
pyrolysis and solid waste management’s approaches for generation of value-added
organic products.
7.2.3 Third-Generation Feedstock for Bioethanol Production
The algae are simple chlorophyll-containing photosynthetic organisms. These are
either phototrophic, i.e., utilizing atmospheric CO 2 to nutrients such as carbohydrate,
or heterotrophic, i.e., utilizing organic carbon sources (Wen and Chen 2003). Algal
biomass is considered as an alternative to 1G and 2G feedstock due to high
productivity, easy cultivation techniques, can use waste water for cultivation, and
convenient harvesting. The algal biomass serves three major purposes, i.e.,
bioethanol production (algal polysaccharides), biodiesel production (algal
bio-oils), and simultaneous waste water treatment. Microalgae and macroalgae are
two major groups of algae and have huge potential for bioethanol production.
7.2.3.1 Microalgae as Feedstock for Bioethanol Production
Microalgae consist of unicellular prokaryotic or eukaryotic photosynthetic
microorganisms. They have simple colony structures and are capable of surviving
under stressed condition (Mata et al. 2010). The total global production of dry algal
biomass is 10,000 ton/year, of which around 7000 ton/year is produced in open
systems (Gris et al. 2013; Lee and Lee 2016). Different species of microalgae used
for production of bioethanol are Chlorella, Spirulina, and Dunaliella. The major
polysaccharide yields are arabinose, galactose, glucose, rhamnose, and xylose with
bioethanol yield potential of 0.234 g/g dry algal biomass having high 11.7 g/L titer
(Ho et al. 2013). Microalgae can also be used for generation of bio-butanol, acetone,
biogas (Marin et al. 2018), eicosapentaenoic acid (Cheng-Wu et al. 2001), omega-3
oil, livestock feed (Besada et al. 2009), pharmaceuticals, and cosmetics (Spolaore
et al. 2006). These sub-products are of high value and thus can facilitate in
minimizing the cost of the overall bioethanol production process (Demirbas 2011).
The chemical composition of the microalgae is affected extensively by the cultivation type and cultivation condition (Burton et al. 2009).
7.2.3.2 Macroalgae as Feedstock for Bioethanol Production
Seaweed or macroalgae have in-habituated to marine form during the course of
evolution. They are broadly classified as Rhodophyceae (red algae), Phaeophyceae
(brown algae), and Chlorophyceae (green algae) based on the type of pigments they
produce (Jung et al. 2013). Major species of red algae are Eucheuma sp. Eucheuma
166
B. Kumar et al.