Page 35 - Energy from Toxic Organic Waste for Heat and Power Generation

Energy Extraction From Toxic Waste Originating From Food Processing Industries 23

3.5.1 Composting
Composting is a typical aerobic digestion process, which converts organic
matter into compost, a humus-rich, earth-like product. The composting
process layout is shown in Fig 3.3. It has been long associated with the treat-
ment of green waste from agricultural farm and garden. With the increasing
limitations in landfill capacity, food waste which previously was earmarked
for landfill is used for aerobic composting [20].
It has been estimated that food waste contributes to around 1/3 of the
compost produced in the EU, with the remaining compost obtained from farm
slurry/manure, sewage sludge, and energy crops. The advantages of compost-
ing include generation of a fertilizer, soil conditioner-like product, reduction
of waste volume, reduction in presence of pathogens, control germination of
weeds in agricultural fields, and elimination of undesirable odorous compounds.
In composting of food waste, microorganisms, including bacteria, fungi,
mold, and actinomycetes, use the organic components in food waste de-
grading them into short chain chemicals, e.g., humic acid. Compost can be
carried out in vessel, aerobic windrow, or aerobic pile. During the compost-
ing process, the temperature often raises to a high level as microbes release
heat (55°C for 5–7 days or 75°C for 2–3 days). This increase in temperature
is responsible for the deactivation of pathogens and weed seeds. The process
layout for the treatment of municipal solid waste is shown in Fig 3.4.

Fig. 3.3 Composting process layout.