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 <i>Methanobacterium</i>, 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.