Page 37 - Energy from Toxic Organic Waste for Heat and Power Generation

Energy Extraction From Toxic Waste Originating From Food Processing Industries 25

During anaerobic degradation of food waste in a landfill, complex or-
ganic materials (carbohydrates, lipids, proteins) are hydrolyzed to soluble
products and ultimately to methane and carbon dioxide through methano-
genesis. If the produced methane is collected, it is typically stored and used
on-site or injected directly into natural gas pipelines, contributing benefits
to the energy sector [1, 21]. The layout of landfill gas production and its
utilization in energy production are shown in Fig. 3.5.
Some fractions in food waste (lignin and lignocellulosic material) are
largely recalcitrant under anaerobic conditions. Therefore, without pre-
treatment, these fractions may inhibit cellulose bioavailability, resulting in
low methane yield. Diversion of food waste from landfills could result in
9% decrease in methane generation, while only a 1% decline in energy
production potential due to the difficulty in capturing methane from the
rapidly degrading labile fractions of food waste [22]. Therefore, landfilling
is perhaps not the optimum mechanism to exploit biogas production by
food waste [23, 24].

3.5.3 Anaerobic Digestion
Anaerobic digestion is a biological process in which biodegradable organic
substrates are decomposed by bacteria in the absence of air, forming gaseous
by-products. The gaseous by-products consist of methane (CH 4 ), carbon

LFG collection system
Power plant
Standby
flare
Water wash
Landfill scrubber
LFG extraction Condenser
blowers

LFG piping
Compressor
Moisture
separator
Chiller
Electricity to power grid

Engine/generator sets

Fig. 3.5 Layout of landfill gas production and its utilization for electricity generation.