1.2 Anaerobic Co-digestion (AcD)

7

Tackles global

warming

Reduces landfill

Cuts green house

gas emission

Circular

economy

Reduces organic

wastes

Cleans municipal

waste waters

Agricultural

manure

Prevents climate

change

Anaerobic

co-digestion

Figure 1.1

Applications of anaerobic co-digestion.

basically referred to as organic wastes generated at its source; it can be available

in many forms and its characteristic depends on the source. It can be available

from a single crop agricultural waste to a blended form as municipal solid waste

(MSW/urban waste) categorized in terms of complexity in defining the exact

composition of waste. Emphasis has been laid on alternative feedstock such as:

●agricultural residues (energy crops),

●commercial food waste (canteen/mess/restaurant),

●retail wastes/fruits and vegetable wastes (peels, press cake),

●animal waste (ranch waste/poultry waste/livestocks processing wastes),

●effluent treatment in industries (dairy wastes, bioprocess industry, sugar

industry),

●garbage waste (MSW),

●sewage sludge (WWTP), etc.

It is still contradictory to classify based on source/origin because some untreated

waste such as food waste may ultimately end up in land fill or may be diverted

to WWTP. The wastes are characterized based on principal nutrient content for

microbes, namely carbohydrates, proteins, and fats. Animal wastes are protein-rich,

while agricultural wastes are carbon-rich with cellulose, hemicelluloses, lignin,

etc. Dairy-industry-generated wastes are fats and protein-rich. Thus each type of

feedstock is unique in composition and based on that requires different approach

for digestion. Feedstock composition should be assessed for certain inhibitors

of methanogenesis, such as nitrates, sulfates as they could support growth of

denitrifiers and sulfate reducers at the expense of methanogens [6, 7]; this tends

to have a drastic effect on hydrogen foraging methanogen population leading to

suboptimum biogas production. Though the organic waste is abundant in nature, its