Syngas biomethanation using trickle bed reactor, impact of external hydrogen addition at high loading rate.xlsx

Syngas is a mixture of CO, CO2, and H2 produced from gasification carbon-containing feedstocks. Syngas can be biologically converted into methane (CH4) using microbial consortia at lower energy input compared to conventional catalytic processes called syngas biomethanation. However, challenges such as H2 limitation, poor gas solubility, and cell damage from mechanical agitation impact conversion efficiency. Trickle bed reactors (TBRs) offer a promising solution to these challenges by enhancing gas-liquid transfer through biofilm formation on packing material while minimizing shear stress, thus improving CH4 productivity. Accordingly, this study investigated the effect of external hydrogen (H2) injection on syngas biomethanation using two thermophilic TBRs at 51 ˚C. One TBR (TBR Control) was fed with syngas containing 15% CO, while the other received additional H2 (TBR Test). Both TBRs effectively converted syngas to CH4, but TBR Test achieved higher performance, with over 90% CH4 conversion efficiency at a gas loading rate of 15 m3/m3·d and a peak CH4 production rate of 4.5 mmol/L_bed·h at 20 m3/m3·d. Volatile fatty acid concentrations remained low. 16S rRNA sequencing analysis showed dominance of Methanobacterium, indicating methanogenesis-driven activity. Overall, the study highlights the benefit of H2 injection during syngas biomethanation and suggests future work should focus on optimizing reactor control to further enhance capacity.