Evaluation of process performance, energy consumption and microbiota characterization in a ceramic membrane bioreactor for ex-situ biomethanation of H2 and CO2

Abstract

The performance of a pilot ceramic membrane bioreactor for the bioconversion of H2 and CO2 to bioCH4 was evaluated in thermophilic conditions. The loading rate was between 10 and 30 m3 H2/m3reactor d and the system transformed 95% of H2 fed. The highest methane yield found was 0.22 m3 CH4/m3 H2, close to the maximum stoichiometric value (0.25 m3 CH4/m3 H2) thus indicating that archaeas employed almost all H2 transferred to produce CH4. kLa value of 268 h−1 was reached at 30 m3 H2/m3reactor d. DGGE and FISH revealed a remarkable archaeas increase related to the selection-effect of H2 on community composition over time. Methanothermobacter thermautotrophicus was the archaea found with high level of similarity. This study verified the successful application of membrane technology to efficiently transfer H2 from gas to the liquid phase, the development of a hydrogenotrophic community from a conventional thermophilic sludge and the technical feasibility of the bioconversion.