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

Simultaneous CO(2) removal with renewable biofuel production can be achieved by methanogens through conversion of CO(2) and H(2) into CH(4). However, the low gas–liquid mass transfer (k(L)a) of H(2) limits the commercial application of this bioconversion. This study tested and compared the gas–liquid mass transfer of H(2) 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(L)a of H(2) and thus enhance the bioconversion of H(2) and CO(2) to CH(4).