Selection of waste-derived inocula for CO2 bio-electro-recycling: Integration of microbial electrosynthesis and anaerobic digestion on charcoal functionalized electrodes

Microbial electrosynthesis (MES) has been widely used to produce volatile fatty acids (VFAs) from CO2. In this technology, the applied potential, the source of the inoculum, and the cathode material are key parameters influencing process performance. This study evaluated different waste-derived inocula to identify the most effective one, which was then used as inoculum in MES bioreactors equipped with activated charcoal-functionalized cathodes at different cathodic potentials: −0.8 V and − 1.0 V vs Ag/AgCl to promote acetate production. Physicochemical parameters were continuously monitored and microbial community composition was characterized. MES experiments were conducted in double-chamber bioreactors using 100 % v/v CO2 feed. The system operating at −1.0 V outperformed the one at −0.8 V MES, converting 60.4 ± 5.1 % of CO2 into acetic acid, with a daily production rate of 98.6 ± 7.5 mg L−1 d−1. Productivity was used to estimate the CO2 emission from biogas from Italian anaerobic digestion plants that can be avoided by converting this CO2 into acetate.