Microbial-electrochemical driven simultaneous biogas upgrading and high-value medium-chain carboxylic acid production.

Biological biogas upgrading is often limited by inefficient hydrogen (H2) gas-liquid mass transfer and low economic returns. To address this, this study developed an innovative microbial-electrochemical system that integrates enhanced H2 delivery in a microbial electrochemical cell with ethanol- and acetate-driven chain elongation by a co-culture of Sporomusa ovata and Clostridium kluyveri, enabling simultaneous biogas upgrading and carbon dioxide (CO2)-to-high-value medium-chain carboxylic acid (MCCA). Systematic optimization of applied external voltage and initial ethanol concentration identified an optimal strategy (3.0 V and 260 mmol L-1 ethanol), simultaneously achieving a biomethane purity of 95.2 % and a high-value MCCA yield of 50.4 mmol L-1. A techno-economic analysis confirmed the strategy's viability, projecting an input revenue of $145,272.4 against an output cost of $59,456.6. Collectively, this work pioneers a novel and economically attractive pathway for biogas valorization by transforming its CO2 component into high-value biochemical.