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220 Refining Biomass Residues for Sustainable Energy and Bioproducts
sorghum (MMT), area harvested (M ha), total supply (MMT), food, seed and indus-
trial (FSI) consumption (MMT), domestic consumption (MMT), and domestic feed
consumption (MMT) from 1960 to 2018. In recent times, a fast and amplified rec-
ognition is found for sorghum near coastal Andhra Pradesh (Chapke et al., 2011,
2016). Sorghum can be cultivated in semiarid tropical regions in a highly effective
manner, whereas there is a miserable growth in the case of other food crops and
best suited in dry land cultivation area also. Sorghum can be cultivated 2 3 times
in a year effectively as it attains maturity within 4 months and it is tolerant to tem-
perature, salinity, and water stress and can also be grown as a rain-fed crop (Yin
et al., 2013). Sorghum grow at temperature between 32 C and 34 C, is considered
as optimum for its growth and photosynthesis, and can also grow within the temper-
ature range of 12 C 37 C.
10.2.3 Composition
Compositional analysis shows that sweet sorghum contains major components such
as lignin and both insoluble (cellulose and hemicellulose) and soluble (glucose and
sucrose) carbohydrates, while its bagasse cellulose, hemicellulose, and lignin con-
tent are 26.3%, 20.0%, and 10.1%, respectively. The composition varies with differ-
ent varieties, type of soil, and ecological conditions. Sorghum biomass constituents
are depicted in Fig. 10.3.
10.2.3.1 Lignin
Lignin is considered the most abundant aromatic and amorphous three-dimensional
phenolic biopolymer. Lignin biosynthesis arises from the polymerization of three
different types of monolignols: (1) p-coumaryl alcohol, (2) sinapyl alcohol, and (3)
coniferyl alcohol responsible for the firm structure. Respective monolignols synthe-
size the lignin units, that is, p-hydroxyphenyl (H), syringyl (S), and guaiacyl (G)
(Sen et al., 2015). Sweet sorghum, forage sorghum, and PS sorghum comprise
10.1%, 10.6%, and 10.4% of total lignin, respectively (Staggenborg, 2016).
10.2.3.2 Cellulose
Cellulose consists of glucose units, which are anhydrous in homopolysaccharide
chain attached by β(1,4)-glycosidic bonds. The presence of inter and intramolecular
hydrogen bonds helps cellulose to have a crystalline structure and also enables the
fibril aggregation. A cellulose unit is generally identified as elementary fibril that
assembles microfibrils formation. Hemicellulose matrices are generally cross-linked
by the microfibril, forming the macro-fibrils, and acts as a barrier to chemical and
enzymatic attacks (Gollakota et al., 2018; Kannam et al., 2017). Sweet sorghum,
forage sorghum, and PS sorghum mainly contain 26.3%, 29.5%, and 29.3% of cel-
lulose, respectively (Staggenborg, 2016).