Improving methane production and anaerobic digestion stability of food waste by extracting lipids and mixing it with sewage sludge

Anaerobic digestion (AD) of FW shows instability due to both the presence of high lipids and accumulation of volatile fatty acids. In this study, AD of food waste (FW) was optimized by removing lipids (LRFW) and by co-digestion with sewage sludge (1:1 w/w on dry matter). The results obtained showed that lipids extraction increased FW methane yield from 400 to 418 mL-g VSadded−1 under mesophilic conditions (35 °C) and from 426 to 531 mL-g VSadded−1 in thermophilic conditions (55 °C). Two degradation phases (k1 and k2) described FW and LRFW degradation. In the thermophilic, LRFW-k1 (0.1591 d−1) was slightly higher than that of FW (k1 of 0.1543 d−1) and in the second stage FW-k2 of 0.0552 d−1 was higher than that of LRFW (k2 of 0.0117 d−1). The majority of LRFW was degraded in the first stage. FW and sewage sludge co-digestion reduced VFA accumulation, preventing media acidification and improving process stability.