Biogas Production from Co-digestion of Substrates: A Review

Sustainable development is the projected demand of all nations at present. Only 20 percent of world’s primary energy requirement is met by renewable sources like solar and wind energy, hydropower, biomass, municipal and agri-wastes. Especially energy recovery from municipal and agri – wastes have gained importance due to two – fold reason: i. waste volume reduction, ii. energy recovery. The present review article focuses onto detailed aspects of some exhaustive research work in the field of energy generation by co-anaerobic digestion of several potential organic sources with cattle manure. Codigestion of substrates have been preferred over mono-digestion due to several benefits associated with it. Carbon to nitrogen (C/N) ratio has been identified as the key parameter for improving the digestion of substrates. The average C/N ratio of 20 – 30 has been stated as optimum for maximum yield of biogas and corresponding methane in it by almost all workers referenced below. Mostly, specific methane production, ultimate methane production, methane production rate has been determined for evaluating the co-digestion process. Improvement in C/N ratio, higher bio-degradability, effective volatile solids (VS) removal, eco-friendly sludge production has been regarded as merits of co-digestion process.