Integrated CO capture and conversion via H-driven CO biomethanation: Cyclic performance and microbial community response.

This study investigated the use of H-driven CO biomethanation for integrated CO capture and conversion (iCCC). Anaerobic chambers containing NaCO-amended microbial growth medium provided with H were inoculated with anaerobic granular sludge. Microorganisms were enriched that could regenerate carbonate by using the bicarbonate formed from CO absorption to generate methane. Multiple absorption-regeneration cycles were performed and effective restoration of CO absorption capacity and stable carbonate recycling via CO biomethanation were observed for CO absorbents adjusted to three different pH values (9.0, 9.5, and 10.0). The pH = 10.0 group had the highest CO absorption capacity; 65.3 mmol/L in the 5th cycle. A slight alkaline inhibition of acetoclastic methanogenesis occurred near the end of regeneration, but had limited impact on the cyclic performance of the iCCC process. Microbial communities were dominated by H-utilizing and alkali-tolerant species that could participate in CO biomethanation and survive under alternating neutral and alkaline conditions.