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

BackgroundApplications 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.ResultsFed-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.ConclusionsFed-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.

Characterization of Core Microbiomes and Functional Profiles of Mesophilic Anaerobic Digesters Fed With Chlorella vulgaris Green Microalgae and Maize Silage

“…The equilibrium between H 2 producers and consumers is crucial in methanogenesis (Wirth et al, 2012;Szuhaj et al, 2016;Bagi et al, 2017). The relative numbers of identified hydrogenase genes were nearly equal in the three reactors ( Figure 7D) (Supplementary Table 3, purple color).…”

Microbial Community Rearrangements in Power-to-Biomethane Reactors Employing Mesophilic Biogas Digestate

“…The headspace of the reactors CH, SH, and CHw12 received 0.81 ± 0.16 mmol H 2 every day. 0.20 ± 0.11 mmol CO 2 was also dosed to sample CHw12 after signs of CO 2 depletion, i.e., day 27-28 (Szuhaj et al, 2016). Controls (CN, SN, CNw12) received an equal volume of N 2 daily.…”

“…The suitability of the biogas reactor effluent, i.e., the digestate, to carry out the bio-P2M conversion has been demonstrated. With the help of microbes inhabiting the biogas producing community, the process can be effectively carried out (Bassani et al, 2015;Szuhaj et al, 2016;Treu et al, 2018a). The AD digestate microbial community offers the possibility of using a catalyst that is practically free of charge and can be replenished continuously.…”

Pyrolysis coupled anaerobic digestion process for food waste and recalcitrant residues: Fundamentals, challenges, and considerations

“…The biological process often adopted in biomass and ROR treatment offers biogas with high CO 2 content, thereby reducing its energy value. In other work, the consumption of hydrogen as a source was reported to improve biogas in their anaerobic digester (90%‐100%) indicating that the reaction was conducted efficiently in the reactor …”