Co-valorization of Food Waste and CO₂ to Produce Volatile Fatty Acids Using Liter-Scale Tubular Microbial Electrosynthesis Cells

Abstract

This study presents the simultaneous conversion of food waste and CO2 into volatile fatty acids (VFAs) using a 6 L tubular microbial electrosynthesis cell (MES). The MES reactor uses a bioanode to convert food waste into current and CO2, while on the cathode, H2 is produced and subsequently consumed by cathode microbes for the conversion of CO2 to VFAs. The study reveals that system performance is impacted by organic loading, applied voltage, and flow rate, and optimal operational conditions achieve a VFA titer of 1763 mg/L with the Coulombic efficiency (CE) exceeding 90% at the anode, highlighting efficient electron recovery from food waste. Resistance analysis indicates that the cathode contributed most to system resistance, while microbial community analysis shows a synergy between fermentative and electroactive bacteria in the anode and dominant acetogens in the cathode, facilitating efficient electron recovery and VFA synthesis, respectively. The research underscores the tubular MES’s potential for sustainable food waste treatment and CO2 valorization into valuable VFAs, contributing to waste management and greenhouse gas mitigation strategies.