Enhanced bioconversion of hydrogen and carbon dioxide to methane using a micro-nano sparger system: mass balance and energy consumption

Abstract

Simultaneous CO₂ removal with renewable biofuel production can be achieved by methanogens through conversion of CO₂ and H₂ into CH₄. However, the low gas–liquid mass transfer (k_La) of H₂ limits the commercial application of this bioconversion. This study tested and compared the gas–liquid mass transfer of H₂ by using two stirred tank reactors (STRs) equipped with a micro-nano sparger (MNS) and common micro sparger (CMS), respectively. MNS was found to display superiority to CMS in methane production with the maximum methane evolution rate (MER) of 171.40 mmol/L_R/d and 136.10 mmol/L_R/d, along with a specific biomass growth rate of 0.15 d⁻¹ and 0.09 d⁻¹, respectively. Energy analysis indicated that the energy-productivity ratio for MNS was higher than that for CMS. This work suggests that MNS can be used as an applicable resolution to the limited k_La of H₂ and thus enhance the bioconversion of H₂ and CO₂ to CH₄.