Simultaneous biohythane and volatile fatty acids production from food waste in microbial electrolysis cell-assisted acidogenic reactor

Abstract

To enhance resource recovery from food waste (FW), a semi-continuous experiment was conducted to study simultaneous biohythane and volatile fatty acids (VFAs) production from it in a microbial electrolysis cell-assisted acidogenic reactor (MEC-AR). Anaerobic fermentation of FW at acid pH (3.71–5.19) produced CH4 through acclimating acid-tolerant methanogens. The MEC-AR with 1.2 V and pH 5.04 ± 0.10 simultaneously produced 2.73 ± 0.05 L/L/d biohythane (with 34.80 ± 1.09% CH4, 14.95 ± 0.86% H2, and 28.74 ± 1.11% H2/(H2+CH4)) and 19.39 ± 0.44 g chemical oxygen demand/L VFAs during steady period. The pH of the fermentation liquid and MEC were the primary factors that influenced the production of biohythane and VFAs. No hydrogen was produced in the reactor at low pH (3.50–4.00) or no applied voltage. The MEC also affected the composition of VFAs with high acetic acid (65.43 ± 2.42%) and low propionic acid (3.71 ± 0.76%) contents and increased the relative abundances of Olsenella and Methanobacterium. Energy analysis showed that the MEC improved the energy efficiency of anaerobic fermentation of FW. This study thus provided a novel, efficient, and applicable strategy for resource recovery and valorization of FW.