ABSTRACT
Anaerobic digestion has been used to stabilize organic wastes, offset greenhouse gas (GHG) emissions, control odors, promote environmental management of nutrients, and produce clean and local renewable energy. The array of organic substrates subjected to anaerobic digestion today varies widely in both diversity and complexity. Livestock manure, from concentrated animal feeding operations (CAFOs), and waste activated sludge (WAS), from wastewater treatment plants (WWTPs) have been traditionally stabilized in on-site anaerobic digesters. Also, an increasing number of CAFOs co-digest livestock manure with imported, high-strength substrates to increase their energy production, take advantage of tipping fees, and improve the economic viability of the farm operation (Scott et al., 2010). In addition, the organic fraction of municipal solid waste (MSW) is separated in certain municipalities in Europe and treated in anaerobic digesters to reduce biomethane emissions from landfills and produce bioenergy. On the other hand, grasses and cereals are grown in biogas plants in Europe with the main purpose of producing bioenergy in anaerobic digesters (Weiland, 2006).
