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

The performance of a pilot ceramic membrane bioreactor for the bioconversion of H-2 and CO2 to bioCH(4) was evaluated in thermophilic conditions. The loading rate was between 10 and 30 m(3) H-2/m(reactor)(3) d and the system transformed 95% of H-2 fed. The highest methane yield found was 0.22 m(3) CH4/m(3)H(2), close to the maximum stoichiometric value (0.25 m(3) CH4/m(3) H-2) thus indicating that archaeas employed almost all H-2 transferred to produce CH4. k(L)a value of 268 h(-1) was reached at 30 m(3) H-2/m(3) reactor d. DGGE and FISH revealed a remarkable archaeas increase related to the selection-effect of H-2 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 H-2 from gas to the liquid phase, the development of a hydrogenotrophic community from a conventional thermophilic sludge and the technical feasibility of the bioconversion.