Page 258 - Refining Biomass Residues for Sustainable Energy and Bioproducts
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228                     Refining Biomass Residues for Sustainable Energy and Bioproducts


         increasing the cellulose from 20 to 30 FPU/g glucose the conversion efficiency of
         cellulose was increased by 8.54% and 13.85%, respectively (Wang et al., 2012).



         10.4   Biofuel production


         Sweet sorghum is akin to sugarcane and the sugar rice juice is present in its stalk.
         The juice contains mixture of sugars, namely, sucrose, glucose, and fructose and its
         proportion varies with the type of variety (Murray et al., 2009). As such, sweet sor-
         ghum plants are tall in nature and tend to produce grains. Sweet sorghum offers
         many advantages in fuel versus food dispute as its grain can be used as feed or
         food, stalks sugar juice can be extracted for direct fermentation to first-generation
         biofuel, and the resultant waste material after extraction of juice, namely, bagasse
         can be used as fodder or heat generation by burning or raw material for the produc-
         tion of second-generation biofuels after pretreatment, that is, partial removal of lig-
         nin to improve the holocellulose availability to produce bioethanol or biogas
         (Molaverdi et al., 2013; Whitfield et al., 2012). As a consequence, there is no need
         of converting the land used for crop production to promotion of fuel crops, as com-
         plete sweet sorghum plant can be used for food from grains, juice for biofuels from
         stalks, and remaining bagasse for fodder (Chohnan et al., 2011; Rohowsky et al.,
         2013). Asian countries, such as China and India, are the leaders in establishing dis-
         tilleries for producing ethanol using sweet sorghum.
           Sweet sorghum is considered the latest generation of bioenergy crop with
         exceedingly proficient system of photosynthesis and is very competent in the con-
         sumption of nutrients from soil. Its high rate of photosynthesis and able to resist the
         deficiency in water and nutrients in soil to grow makes it as a suitable crop for
         bioenergy production. The crop can be cultivated in any type of land and can be
         used as food, fuel, fodder, and fiber because it is adjusted easily for cultivation, and
         it can tolerate abiotic stresses (Zegada-Lizarazu and Monti, 2012). It is considered
         as an ideal feedstock for biofuel production over crops such as sugarcane, corn, and
         sugar beet due to its uptake of nitrogen from soil efficiently (Almodares and Hadi,
         2009).


         10.4.1 Bioethanol
         Ever-decreasing fossil-fuel resources and emission of GHGs can be reduced by con-
         verting sweet sorghum for biofuel production that is bioethanol. Around 3500 and
         2500 L of crude oil equivalents can be saved per hectare of area of cultivation of
         sweet sorghum, if its juice and bagasse are completely converted to ethanol and
         electricity and only juice to ethanol, respectively (Kim and Day, 2011; Sipos et al.,
         2009).
           Bioethanol can be obtained from different sections of sweet sorghum. Sipos
         et al. (2009) reported that the ratio of grains, leaves, and stem were around 8, 16,
         and 76, respectively. The composition of sweet sorghum is as follows: moisture
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