A feasibility study on the bioconversion of CO2 and H2 to biomethane by gas sparging through polymeric membranes.

Abstract In this study, the potential of a pilot hollow-fiber membrane bioreactor for the conversion of H 2 and CO 2 to CH 4 was evaluated. The system transformed 95% of H 2 and CO 2 fed at a maximum loading rate of 40.2  m H 2 3 / m R 3 d and produced 0.22 m 3 of CH 4 per m 3 of H 2 fed at thermophilic conditions. H 2 mass transfer to the liquid phase was identified as the limiting step for the conversion, and k L a values of 430 h −1 were reached in the bioreactor by sparging gas through the membrane module. A simulation showed that the bioreactor could upgrade biogas at a rate of 25  m 3 / m R 3 d , increasing the CH 4 concentration from 60 to 95%v. This proof-of-concept study verified that gas sparging through a membrane module can efficiently transfer H 2 from gas to liquid phase and that the conversion of H 2 and CO 2 to biomethane is feasible on a pilot scale at noteworthy load rates.