7.2.2.2.1.3 Bagasse for Bioethanol Production
Bagasses are obtained after processing of the starchy tuber crop “cassava and
sorghum” and sugar-rich crop “sugarcane” cultivated mainly in Asian, Latin American, and African countries. India is home to almost 1100 cassava processing units
which generate a huge amount of bagasse after processing of approximate 8.74
million tons of cassava (Mohapatra et al. 2019). These bagasses are also rich in
carbohydrate polymer, i.e., 30–35% (Ray and Swain 2011). It is estimated that 1 ton
of cassava bagasse can lead to the generation of 114 L of bioethanol (Sangodoyin
and Amori 2013). The fifth most important cereal crop grown in the world is
sorghum. A by-product obtained after sorghum processing, i.e., sorghum bagasse,
consists of high amount of carbohydrate polymer (35.5% hemicellulose, 44.4 %
cellulose) and very low lignin (3.5%) and thus can be converted to ethanol very
easily due to low lignin recalcitrance (Dogaris et al. 2009).
The leftover residue after extraction of juice from sugarcane is known as sugarcane bagasse; it is a cheap residue and has an estimated production of 317–380
million ton/year (Sánchez 2009). It has high carbohydrate content of ~70–80%
(cellulose and hemicelluloses) and ~20–30% lignin with low 1.9% ash content
(Peng et al. 2009). This bagasse may be immediately available at their processing
site where crops are processed. The integrated biorefinery where processing of crop
followed by its conversion to bioethanol is a cost-efficient method (Furlan et al.
2013).
7.2.2.2.1.4 Sweet Potato Residues (SPRs) for Bioethanol Production
As discussed in starch-based biomass, sweet potato accounts for 10% residues after
extraction of starch and can be used as bioethanol generation substrate. China is the
leading sweet potato producer with an annual production of ~71 million tons. The
processing units for sweet potato in China produce around 2 million tons of sweet
potato residues which because of their high viscosity remain unutilized and can act
as environmental pollutants. By enzymatic breakdown, these residues can be substantially used for sugar and ethanol generation (Izmirlioglu and Demirci 2012).
7.2.2.2.1.5 Oil-Palm Biomass for Bioethanol Production
Once the oil is extracted from the palm fruit bunches, a large amount of empty fruit
bunches, fronds, and trunks are left out. On per hectare basis, 40 tons of empty fruit
brunch, 10.5 tons of fronds, and 2.8 tons of trunks are generated per year; these
residues can act as substrates for bioethanol production. The high cellulosic content
of fronds (31.0–32.0%) and trunks (39.9–41.0%) makes it more suitable for cellulosic ethanol generation. However, even the cellulose content in empty fruit bunches
are less, i.e., 7.7–14.7%, but applying enzymes such as amylase and cellulase can
result in 96.3% glucose yield with ethanol yield of approximately 93.5% (Eom et al.
2015)
7.2.2.2.1.6 Bast Fiber for Bioethanol Production
Bast crops are naturally occurring non-woody plant and can be potentially considered as energy crop due to several advantages such as it’s capability of growing on
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B. Kumar et al.
Bagasses are obtained after processing of the starchy tuber crop “cassava and
sorghum” and sugar-rich crop “sugarcane” cultivated mainly in Asian, Latin American, and African countries. India is home to almost 1100 cassava processing units
which generate a huge amount of bagasse after processing of approximate 8.74
million tons of cassava (Mohapatra et al. 2019). These bagasses are also rich in
carbohydrate polymer, i.e., 30–35% (Ray and Swain 2011). It is estimated that 1 ton
of cassava bagasse can lead to the generation of 114 L of bioethanol (Sangodoyin
and Amori 2013). The fifth most important cereal crop grown in the world is
sorghum. A by-product obtained after sorghum processing, i.e., sorghum bagasse,
consists of high amount of carbohydrate polymer (35.5% hemicellulose, 44.4 %
cellulose) and very low lignin (3.5%) and thus can be converted to ethanol very
easily due to low lignin recalcitrance (Dogaris et al. 2009).
The leftover residue after extraction of juice from sugarcane is known as sugarcane bagasse; it is a cheap residue and has an estimated production of 317–380
million ton/year (Sánchez 2009). It has high carbohydrate content of ~70–80%
(cellulose and hemicelluloses) and ~20–30% lignin with low 1.9% ash content
(Peng et al. 2009). This bagasse may be immediately available at their processing
site where crops are processed. The integrated biorefinery where processing of crop
followed by its conversion to bioethanol is a cost-efficient method (Furlan et al.
2013).
7.2.2.2.1.4 Sweet Potato Residues (SPRs) for Bioethanol Production
As discussed in starch-based biomass, sweet potato accounts for 10% residues after
extraction of starch and can be used as bioethanol generation substrate. China is the
leading sweet potato producer with an annual production of ~71 million tons. The
processing units for sweet potato in China produce around 2 million tons of sweet
potato residues which because of their high viscosity remain unutilized and can act
as environmental pollutants. By enzymatic breakdown, these residues can be substantially used for sugar and ethanol generation (Izmirlioglu and Demirci 2012).
7.2.2.2.1.5 Oil-Palm Biomass for Bioethanol Production
Once the oil is extracted from the palm fruit bunches, a large amount of empty fruit
bunches, fronds, and trunks are left out. On per hectare basis, 40 tons of empty fruit
brunch, 10.5 tons of fronds, and 2.8 tons of trunks are generated per year; these
residues can act as substrates for bioethanol production. The high cellulosic content
of fronds (31.0–32.0%) and trunks (39.9–41.0%) makes it more suitable for cellulosic ethanol generation. However, even the cellulose content in empty fruit bunches
are less, i.e., 7.7–14.7%, but applying enzymes such as amylase and cellulase can
result in 96.3% glucose yield with ethanol yield of approximately 93.5% (Eom et al.
2015)
7.2.2.2.1.6 Bast Fiber for Bioethanol Production
Bast crops are naturally occurring non-woody plant and can be potentially considered as energy crop due to several advantages such as it’s capability of growing on
164
B. Kumar et al.