Integrated CO2 capture and conversion via H2-driven CO2 biomethanation: Cyclic performance and microbial community response

Abstract

This study investigated the use of H₂-driven CO₂ biomethanation for integrated CO₂ capture and conversion (iCCC). Anaerobic chambers containing Na₂CO₃-amended microbial growth medium provided with H₂ were inoculated with anaerobic granular sludge. Microorganisms were enriched that could regenerate carbonate by using the bicarbonate formed from CO₂ absorption to generate methane. Multiple absorption-regeneration cycles were performed and effective restoration of CO₂ absorption capacity and stable carbonate recycling via CO₂ biomethanation were observed for CO₂ absorbents adjusted to three different pH values (9.0, 9.5, and 10.0). The pH = 10.0 group had the highest CO₂ 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 H₂-utilizing and alkali-tolerant species that could participate in CO₂ biomethanation and survive under alternating neutral and alkaline conditions.

Keywords: CO(2) absorption; CO(2) conversion; Carbonate recycling; Methanogenesis; Regeneration.