Page 264 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Sweet sorghum: a potential resource for bioenergy production 233

biomass is subjected to temperatures below 900 C with deprived environment of
oxygen to form a carbon-rich solid material. The yield of biochar in fast pyrolysis,
gasification, torrefaction, hydrothermal carbonization, and slow pyrolysis is B12%,
B10%, B80%, 50% 80%, and B35%, respectively (Godlewska et al., 2017;
Kambo and Dutta, 2015; Zhang et al., 2019b). In recent times, characteristics, such
as large surface area, high degree of porosity, and the presence of functional groups
on the surface, have drawn much attention to biochar as a potential solution to
resolve environmental management problems (Zhang et al., 2019b). Biochar have
been utilized for the soil remediation, GHG reduction (including CO 2 capturing),
efficient sorbent material, and energy production as a solid fuel act as a catalyst
and high C-rich compositing material (Huang et al., 2015; Qambrani et al., 2017;
Zhang et al., 2019b).
Biochar of sorghum biomass contains 14.7% of volatile matter, 62.8% of fixed
carbon, and 18.7% of ash content, which is obtained from fast-pyrolysis process. In
the ultimate analysis, C, H, N, and O contents are 69.0%, 2.7%, 0.59%, and 27.6%
of total weight percentage, respectively. Heating values, that is, HHV and LHVs,
are 23.11 and 22.51 MJ/kg, respectively, that is higher as compared to that of sor-
ghum biomass. The morphology of biochar shows that it is highly porous in nature
which contains 1 20 μm of regular pores. It can be exploited to produce activated
carbon as it contains higher amount of C. In addition, it can be applied for the
remediation of metal ions, pesticides, polycyclic aromatic hydrocarbons, etc.
(Soudek et al., 2017; Yin et al., 2013).
Various researchers have found that biochar application in soil fertilization, car-
bon sequestration, plant growth, and the improvement of soil structure has resulted
in improved sorghum growth and yield under sandy desert soils. The sorghum crop
yield was found to increase when biochar was applied at the rate of 22 Mg/ha
(Laghari et al., 2015). Similarly, Blackwell et al. (2015) observed that addition of
biochar and biochar mineral complex enhanced the colonization of mycorrhiza
and nutrition in wheat and sorghum. Moreover, sorghum biochar has been used to
increase the biomass of winter wheat (Sigua et al., 2015). In order to remove toxic-
ity of Cd, Cu, and Pb, sorghum seed germination was increased in the presence of
biochar (Soudek et al., 2017).

10.4.4 Value-added products

Sorghum bagasse and sorghum syrup have major application in the production of
bioethanol, biogas, biochar, biooil, and syngas. However, other coproducts, such as
processed bagasse, steam, foam, and forth, obtained during the syrup or ethanol
production and waste vinasse generated during the dewatering process can be fur-
ther utilized for the energy production and ruminant or poultry feed (de Resende
et al., 2006; Srinivasa Rao et al., 2012; Ray et al., 2019).
The processed or discarded sorghum biomass can be utilized for the production
of solid biofuels (briquettes). Gross and net calorific values of briquettes based on
sweet sorghum biomass were 18.9 and 17.7 MJ/kg, respectively. Calorific values of
sorghum briquettes were comparable with the sawdust briquettes. Sorghum residual