Optimization of Biogas Production and In-Situ Upgrading via Hydrogenotrophic Methanogenesis in a Lab-Scale UASB Reactor

The increasing demand for sustainable bioenergy has strengthened interest in biogas upgrading technologies that aim to produce pure CH4 by separating CO2 and all other impurities. This study investigates the in situ biomethanation of CO2 by feeding H2 into a 7 L UASB anaerobic digester treating synthetic and potato-processing wastewater. Initially, the reactor operated under varying HRT and OLR to assess baseline performance. Following stabilization, H2 was introduced either into the feed line or the recirculation line via a microbubble generation system. Hydrogen addition to the feed increased biogas production by 18%, methane concentration to 70.9%, and reduced CO₂ to 5.2%. Transitioning hydrogen injection to the recirculation line improved methane purity (78.8%) and TOC removal (74.3%), while doubling hydrogen flow further enhanced biogas production (4.6 ± 0.7 L/day) and increased TOC removal to 83.97%, despite a slight drop in methane content (73.1%). Across all conditions, hydrogen feed minimized VFA accumulation and supported syntrophic stability. Overall, in-situ hydrogen injection proved effective for enhancing methane yield and biogas quality, highlighting its potential for sustainable biogas biomethanation from industrial wastewaters.