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236 Refining Biomass Residues for Sustainable Energy and Bioproducts

ground near the field, the juice is converted into syrup which is followed by its storage
in cans and transportation to industrial site for further processing into ethanol, thereby
increasing the storage time up to 6 8 months before processing it for ethanol produc-
tion. As per 2009 estimates, conversion cost of 1 kg syrup to ethanol was US$0.41.
Similarly, pilot studies were also conducted by Indian Institute of Millets
Research on conversion of sweet sorghum to ethanol with the help of distilleries.
An ethanol yield of 25 40 L/t of crushed sorghum stalk was observed (Dayakar
Rao et al., 2004). The techno-economic feasibility of ethanol production was also
studied by National Research Center for Sorghum, Hyderabad, Andhra Pradesh in
collaboration with M/s. Renuka Sugars Ltd. (Belgaum, Karnataka). They found that
the ethanol production cost is 13.11 INR/L of sweet sorghum juice, which is lower
than the price from sugarcane bagasse (14.98 INR/L of sugarcane juice). These
findings establish sorghum as one of the emerging feedstocks for bioethanol pro-
duction (Basavaraj et al., 2013; Dar et al., 2018).

10.7 Conclusion

Sweet sorghum is an energy-rich crop as it is grown popularly in the world. Its lig-
nin content is lower and the holocellulose availability in the biomass can be easily
utilized for biofuel production after necessary pretreatment. Efficient pretreatment
techniques have been established depending upon the biofuel production for conver-
sion of sweet sorghum biomass, stalks, grain, sugar syrup, and bagasse. Solid, liq-
uid, and gaseous biofuels, namely, biochar, briquettes, pellets, bioethanol, butanol,
hydrogen, and methane, can be produced and it can be utilized for thermal, power,
or transport applications. Considering the need of the hour and environmental per-
spectives, biofuel production from sweet sorghum is valuable than producing elec-
tricity as many cheaper options are available to generate electricity from
nonrenewable and renewable sources. As India is vigorously focusing in blending
ethanol in gasoline fuels, the lack of quality renewable liquid biofuel provides a
better opportunity for conversion of sweet sorghum to liquid biofuel that gets a
huge market and environment-friendly fuel rather than producing electricity. Sweet
sorghum residues after grain harvesting cannot be simply burnt or discarded in the
fields as its coproducts have huge market potential. Methods need to be optimized
and explored for complete conversion of sweet sorghum to useful biofuel with inno-
vations that cost less to the end user.

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