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

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 fermen-tation 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.