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28 Bioconversion of Food Waste to Wealth – Circular Bioeconomy Approach

environmentally safe product. We have successfully developed procedure to com-

post the food waste into fertilizers and incinerate the food waste for the generation

of energy (heat). However, we should also account for the harmful issues associated

with the incineration like CO2 emission, air pollution, and generation of dioxins

during their combustion [45].

Food industries generate numerous byproducts and waste streams which are rich

in lipids, carbohydrates, and proteins, and these waste streams generate negative

impact on the environment. These compounds can be potentially transformed into

revenue streams like biofuels, animal feeds, nutraceutical ingredients, etc. Most

industries rely on the chemical reactions (esterification) for value-added products,

like esterification of oil with alcohol to produce biodiesel, esterification of sugar to

produce surfactants, esterification of starch for biodegradable plastics, etc. However,

most industries practice chemical process for valorizing the food waste involving

chemical catalyst and energy, which results in another byproducts [46].

Traditional chemical reactions with catalyst can be replaced with biocatalysts

(enzymes) and generate the revenue without high energy input. Enzymes (also

called as biocatalysts) are water-soluble proteins which can enhance chemical

reactions like chemical catalyst with outstanding specificity, high regio- and

stero-selectivity, with “green, eco-friendly” label. Enzymatic treatment is a process

of digesting the food waste and converting the food waste nutrients (carbohydrates,

proteins, and fat) into smaller and more digestible nutrients like amino acids, free

sugars, and fatty acids [47]. These enzymatic treatments are considered as a “green”

method due to the absence of harmful chemicals and possibility of achieving

value-added products without any degradation or damage. For instance, enzymatic

treatment of defatted rice bran yielded glucose, amino acids, and peptides without

any damage [48].

On the other hand, application of food waste for the conversion of bioenergies

has attracted more attention as they are renewable and clean energy. Researchers

successfully reported the production of biomethane through anaerobic digestion of

food waste and sewage treatment plant sludge (co-digestion technique), transester-

ification of cooking oil to produce biodiesel, and bioethanol from fermentation of

carbohydrate-rich food waste. Though researchers succeeded in the production of

bioenergy from food waste, the conversion ratio falls between 40% and 70% only with

significant energy input up to 184.4 kWh/t food waste [49, 50]. The main reason for

the reduction in conversion rate is due to the non-accessible portion of organic mat-

ter for microbial utilization for bioenergy production. It is possible to enhance the

production efficiency by prior hydrolysis of food waste through enzymatic pretreat-

ment. Figure 28.3 shows the different production techniques and the corresponding

enzymatic pretreatment for the production of bioenergy from food waste.

Similar to food waste, sludge from the sewage treatment plant is another environ-

mental challenge due to the prediction of billions tons of sewage and wastewater

sludge every year. The presence of valuable resources like organic matter, energy,

and nutrients can make a suitable combination with food waste for an excellent

substrate for the anaerobic digestion. Yin et al. [51] investigated the production

of biomethane for the collected food waste from university canteen and sewage