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Bioenergy generation from agricultural wastes and enrichment of end products 347

Various alkalis, such as NaOH, Ca(OH) 2 , and KOH, are used, which degrade the
lignin and carbohydrate link. Liquid ammonia water mixture has been used by
many researchers to pretreat lignocellulosic biomass (Dale et al., 1996). It is a
dry-to-dry process performed by adding liquid ammonia and prewet substrate in a
pressurized reactor and operated for 5 45 min. Apart from this, oxidative and ionic
liquid pretreatments are also emerging nowadays. Ionic liquids are green solvents
with strong chemical stability, low vapor pressure, and nonflammability and are
used to pretreatment of lignocellulosic waste for the production of sugar.
Organosolv pretreatment is another technique that is performed in the temperature
range of 100 C 250 C with solvents, such as methanol and glycerol. This extracts

lignin and solubilized hemicelluloses by breaking the bonds between hemicelluloses
and lignin as well as glycosidic bond in hemicellulose (Zhao et al., 2009).
Among other pretreatment techniques, thermochemical pretreatment is a combi-
nation of both thermal and chemical treatment to improve the product yield and
lessen the time required for the conversion.

15.5 Routes for conversion

The rapid development in the country in every sector has increased the use of con-
ventional energy sources and it has also created pressure on the present generation
regarding the depletion of fossil fuel reserve. In addition to it, the use of these fuels
also releases toxic gases (SO x ,NO x ,CO 2 ) to the environment, which lead to the
change in the environmental conditions and ultimately to the global warming.
Therefore, from the last few decades, there has been an increasing interest in the
treating biomass as valuable resource rather than a reject. Biomass has enough
potential and availability to be converted into valuable products, such as biooil, bio-
gas, chemicals, or fertilizers. In addition, it will put a curtain on biomass disposal
or land filling, lessen the environmental problems, and will provide wealth and
employment.
At present irrespective of various technologies, biochemical and thermochemical
conversion processes have gathered much attention in fruitful utilization of agricul-
tural wastes. Depending upon the type, extent, and properties of biomass, any of the
technologies can be used. In general, biochemical conversion processes need
microbes and bacteria for the biomass degradation, thus biomass with lesser amount
of lignin is preferred. For thermochemical processes, lesser amount of moisture is
preferred as it reduces the use of extra energy for drying.

15.5.1 Biochemical conversion
Biochemical conversion of agricultural biomass waste to bioenergy is an
environment-friendly and sustainable technique. It involves the use of different
microbes and bacteria that helps in decomposition of biomass waste to energy. AD
and fermentation are the two important biochemical processes.