Page 313 - Refining Biomass Residues for Sustainable Energy and Bioproducts

282 Refining Biomass Residues for Sustainable Energy and Bioproducts

Figure 13.4 Distribution of various carbohydrate forms in rice straw.

Biofuels can be produced from the cellulosic material of rice residues by convert-
ing them into fermentable sugars and then into the fuel product by application of cer-
tain microorganisms or enzymes. The availability of the carbohydrates in rice
residues is mainly hindered by the presence of lignin in the plant cell wall and needs
to be removed. Several pretreatment methods (Fan etal.,1982; Schultz etal.,1983;
Hormeyer et al., 2009; Hahn-H¨ agerdal et al., 2001; Bollok, 1999; Soni et al., 2010)
have been developed to degrade lignin materials and for solubilization of hemicellu-
lases resulting in fermentable sugars (Fig. 13.5). The response of rice straw varieties
to various chemical pretreatments shows higher enzymatic digestibility as compared
to that of wheat straw (Wu et al., 2013). It reveals that rice straws are a more feasible
option to be used as a source of biofuel. Instead of burning them by conventional
practices, the use of rice straw as a feedstock for the production of bioethanol would
make it the world’s single largest feedstock for the production of second-generation
ethanol (Harun et al., 2013; Karimi et al., 2016; Kim and Dale, 2004).

13.5 Biofuel as a renewable source of energy

The development of renewable energy technologies is essential to reduce the
demand on conventional energy resources. Fossil fuels have played a major role
toward advancement in the field of transportation and industrialization, as an energy
source. Their high heating capability, combustion characteristics, widespread