Electrochemical biogas upgrading for high-value multiphase resource recovery via CO2 conversion and sulfur-containing impurity valorization: Advances, challenges, and perspectives.

Biogas upgrading is essential for expanding biomethane utilization, but conventional separation-based technologies such as pressure swing adsorption, membrane separation, and chemical absorption often remove CO2 and trace impurities without recovering their resource value. Electrochemical biogas upgrading offers a route to integrate gas purification with electrically driven CO2 capture or conversion, impurity valorization, and multiphase product recovery. This review summarizes recent advances in electrochemical biogas upgrading from the perspective of gas-, liquid-, and solid-phase resource recovery. Gas-phase pathways include CH4 enrichment, separated CO2 recovery, CO production, and H2-enriched fuel gases; liquid-phase pathways focus on the recovery of formate, acetate, and medium-chain fatty acids; solid-phase pathways recover elemental sulfur and mineral carbonates. Particular attention is given to route and configuration selection under realistic biogas conditions, including diluted CO2, CH4-rich backgrounds, sulfur-containing impurities, cathode-anode coupling, product separation, and downstream use. System-level sustainability and techno-economic drivers are further discussed, including electricity carbon intensity, product substitution, downstream separation, stack durability, and the comparability of published TEA/LCA assessments. Despite substantial laboratory-level progress, long-duration validation using real-biogas and standardized impurity-tolerance data remain limited. By aligning real-biogas operation, low-carbon electricity, and on-site reuse, electrochemical biogas upgrading may evolve from a CO2 removal process into an integrated platform for biomethane production, impurity valorization, and circular water-energy-carbon management.