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412 Refining Biomass Residues for Sustainable Energy and Bioproducts

anaerobic processing and the resultant results of the assimilation are carbon dioxide
(CO 2 ) and methane (CH 4 ). The AD stages and their products are shown in
Fig. 18.3.

C 6 H 12 O 6 ! 3CO 2 1 3CH 4

Hydrolysis is the way toward breaking large organic polymer chains and
dissolving the smaller atoms into solution. For the AD, FW is hydrolyzed initially
because the waste biomass contains the complex organic polymers, and it can be
converted into a soluble and digestible molecule by anaerobic bacteria. The resul-
tant products of hydrolysis are simple sugars, amino acids, and fatty acids. The pro-
ducts of hydrolysis which having the smaller chain length can be directly used by
the methanogens, and the products having the longer chain length should be catabo-
lized into the compounds which can be directly used by the methanogens through
acidogenesis and acetogenesis (Sleat and Mah, 2006; Boone and Mah, 2006).
Acidogenesis and acetogenesis are catabolic processes in which a large complex
polymer chain can be broken down into alcohols, carbonic acids, and volatile fatty
acids (VFAs) and acetic acid. Methanogenesis is a biological process of terminal
stage of AD in which the smaller chain length molecules or catabolized products
can be converted into biogas (methane), CO 2 , and water through the fermentation
process. Different important key stages of AD, bacterial genera used for their
respective process, and their general equation are mentioned in Table 18.1 (Bryant,
1979; Schink, 1997).

18.5 Food waste—interactions of biorefineries

FWs obtained from different sources, such as manufacturing industries, wholesale
and retail, food services, and households, should be interacting with biorefinery
process for valorization. Through an interaction the waste can be converted into
different valuable products.

18.5.1 Biorefinery process

Biorefinery process includes different techniques through which the FW can be
converted into useful products. Biorefineries are not another improvement; they are
starting at now associated, for example, in the sustenance business for a long time.
Three different states of advances for energy-driven biorefineries can be perceived:
commercial-scale vitality-driven biorefineries, demonstration-scale energy-driven
biorefineries, and conceptual energy-driven biorefineries (Hingsamer and
Jungmeier, 2019). There are seven different types of biorefineries that can be classi-
fied based on their sources: agricultural, cereal, oilseed, green, lignocellulosic, for-
estry, and industrial waste. The three main qualities of a biorefinery are as follows:
The coupled age of vitality (e.g., vaporous or fluid biofuels) and materials (e.g., synthetic
compounds, sustenance, and feed)