Comprehensive experiences on the operation of a full-scale continuous dry anaerobic digestion plant treating mechanically sorted OFMSW

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) is a crucial waste management method for the diversion of organics from landfills to decrease greenhouse gas emissions while enabling energy recovery. A number of dry AD systems treating OFMSW have notably increased over the last two decades. In this study, mono-digestion of mechanically sorted OFMSW and co-digestion of OFMSW, chicken manure and WWTP sludge were evaluated using triplicate full-scale digesters. Results demonstrated that 5–6.6 m³_biogas/m³_reactor.day biogas could be produced at an organic loading rate (OLR) of 10.5–12 kg TVS/m³.day, with an HRT of 16–18 days. Beyond this threshold, further increases in OLR resulted in reduced gas production due to ammonia inhibition as a result of broiler chicken manure overload. Biogas yield decline started when the chicken manure content of the feed was increased to 10% (w/w) and accompanied with the VFA/TA ratio rising above 0.8. Process instability and a sharp drop in biogas productivity were observed when the feed contained more than 20% (w/w) chicken manure, where VFA/TA ratio exceeded 1.0. Results underline the importance of balancing different properties (e.g., degradability, carbon to nitrogen (C/N) ratio) of co-substrates to optimize the biogas yield and to ensure process stability.