title: Conversion of H2 and CO2 to CH4 and acetate in fed-batch biogas reactors by mixed biogas community: a novel route for the power-to-gas concept.
abstract: BACKGROUND
  Applications of the power-to-gas principle for the handling of surplus renewable electricity have been proposed. The feasibility of using hydrogenotrophic methanogens as CH4 generating catalysts has been demonstrated. Laboratory and scale-up experiments have corroborated the benefits of the CO2 mitigation via biotechnological conversion of H2 and CO2 to CH4. A major bottleneck in the process is the gas-liquid mass transfer of H2.
  
  
  RESULTS
  Fed-batch reactor configuration was tested at mesophilic temperature in laboratory experiments in order to improve the contact time and H2 mass transfer between the gas and liquid phases. Effluent from an industrial biogas facility served as biocatalyst. The bicarbonate content of the effluent was depleted after some time, but the addition of stoichiometric CO2 sustained H2 conversion for an extended period of time and prevented a pH shift. The microbial community generated biogas from the added α-cellulose substrate with concomitant H2 conversion, but the organic substrate did not facilitate H2 consumption. Fed-batch operational mode allowed a fourfold increase in volumetric H2 load and a 6.5-fold augmentation of the CH4 formation rate relative to the CSTR reactor configuration. Acetate was the major by-product of the reaction.
  
  
  CONCLUSIONS
  Fed-batch reactors significantly improve the efficiency of the biological power-to-gas process. Besides their storage function, biogas fermentation effluent reservoirs can serve as large-scale bio CH4 reactors. On the basis of this recognition, a novel concept is proposed, which merges biogas technology with other means of renewable electricity production for improved efficiency and sustainability.
authors.affiliation: Department of Biotechnology, University of Szeged, Közép fasor 52, Szeged, 6726 Hungary.
authors.forename: Márk
authors.initials: M
authors.lastname: Szuhaj
authors.affiliation: Department of Biotechnology, University of Szeged, Közép fasor 52, Szeged, 6726 Hungary.
authors.forename: Norbert
authors.initials: N
authors.lastname: Ács
authors.affiliation: Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, Temesvári krt. 62, Szeged, 6726 Hungary.
authors.forename: Roland
authors.initials: R
authors.lastname: Tengölics
authors.affiliation: Department of Biotechnology, University of Szeged, Közép fasor 52, Szeged, 6726 Hungary.
authors.forename: Attila
authors.initials: A
authors.lastname: Bodor
authors.affiliation: Department of Biotechnology, University of Szeged, Közép fasor 52, Szeged, 6726 Hungary ; Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, Szeged, 6726 Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Rákhely
authors.affiliation: Department of Biotechnology, University of Szeged, Közép fasor 52, Szeged, 6726 Hungary ; Department of Oral Biology and Experimental Dental Research, University of Szeged, Tisza L. krt. 64, Szeged, 6720 Hungary ; Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, Szeged, 6726 Hungary.
authors.forename: Kornél L
authors.identifier: 0000-0002-3926-0497
authors.initials: KL
authors.lastname: Kovács
authors.affiliation: Department of Biotechnology, University of Szeged, Közép fasor 52, Szeged, 6726 Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Bagi
keywords: Biomethane; Carbon dioxide; Hydrogen; Hydrogenotrophic methanogens; Power-to-biomethane (P2B); Power-to-gas