Page 253 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Sweet sorghum: a potential resource for bioenergy production 223

Figure 10.5 Other components and energy values from sweet sorghum. Total energy
obtained from sorghum, wheat, and rice (A); mineral contents from sweet sorghum (B);
amino acid composition of sweet sorghum (C); fat constituents obtained from sweet sorghum
(D); comparison of total dietary fibers (including soluble dietary fibers and insoluble dietary
fibers) in sorghum bran, bagasse, and biomass (E); and extracted vitamins from sweet
sorghum in terms of percentage (F) (Qiu et al., 2017; Ratnavathi et al., 2016).

pretreatments. In addition, generation of hazardous chemicals and other by-products
are negligible. Physical pretreatments include different types of methods, such as
milling, grinding, chipping, freezing, and extrusion. However, physical pretreat-
ments are the first stage of pretreatments so secondary treatments produce ethanol
and other products (Rabemanolontsoa and Saka, 2016).
Milling reduces the size of lignocellulosic substrates, which is the initial stage.
Further, chipping process reduces the size of the biomass up to 10 30 mm, whereas
grinding reduces the size of the biomass up to 0.2 0.5 mm. Two-roll milling, disk
milling, ball milling, hammer milling, and colloid milling are a few types of milling
processes that are used for pretreatment (Rabemanolontsoa and Saka, 2016).
Generally, sorghum straw or bagasse are milled initially and, thereafter, utilized for
other pretreatments for the production of ethanol (McIntosh and Vancov, 2010).
Steam explosion is an efficient physical pretreatment that weakens the lignocellu-
lose components. In this pretreatment, biomass is generally exploited to steam