Effects of thermal pre-treatment on anaerobic co-digestion of municipal biowastes at high organic loading rate

• Co-digestion of FW, FVR with DAS can enhance the stability of biogas process.
• The threshold weight ratio of DAS is 30% when the digester run at high OLR.
• Thermal pretreatment decreases the biodegradability of FW and FVR.
• Co-digestion of FW, FVR with thermal treated DAS is suggested.

Anaerobic co-digestion of thermal pre-treated municipal biowaste (MBW) is a field of research that has had limited contributions to date. In this study, laboratory-scale semi-continuously fed anaerobic digesters treating thermally treated and non-treated MBW were operated at high organic loading rates (OLR). The results show that the methanogenesis process was inhibited by the accumulated volatile fatty acids when 30% (w/w) of dewatered activated sludge (DAS) was co-digested with food waste (FW) and fruit/vegetable residue (FVR) at high OLR ⩾ 10 kg volatile solid m−3 d−1. Co-digestion with thermal hydrolysed DAS can significantly improve digester performance. In contrast to DAS, some adverse effects of thermal pretreatment on the biodegradability of FW and FVR were observed. Therefore, co-digestion of FW, FVR with thermally treated DAS is suggested as an alternative to promote high methane production and process stability.