Anaerobic co-digestion of organic fraction of municipal solid waste (OFMSW): Progress and challenges

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) offers the possibility of a clean and renewable energy source – i.e. biogas. However, OFMSW lacks certain characteristics that may limit its efficacy as such a resource. Bio-resources such as sewage sludge and animal wastes have these characteristics and so may be used to enhance OFMSW's digestion. Anaerobic co-digestion (AcoD) of OFMSW with sewage sludge has been extensively studied and applied successfully at full-scale. Pre-treatments can increase substrate biodegradability and so biogas yield, but these may need further investigation to determine economic viability. Mathematical modeling has been shown useful in aiding selection of appropriate combinations of substrates and pretreatment for co-digestion (e.g. substrate type and mix ratio). This review also considers the fate of the digestate following such anaerobic co-digestion. The difficulties in implementation of the co-digestion approach need not necessarily be technical in nature but can be due to management issues.