title: Biomass retention on electrodes rather than electrical current enhances stability in anaerobic digestion.
abstract: Anaerobic digestion (AD) is a well-established technology for energy recovery from organic waste streams. Several studies noted that inserting a bioelectrochemical system (BES) inside an anaerobic digester can increase biogas output, however the mechanism behind this was not explored and primary controls were not executed. Here, we evaluated whether a BES could stabilize AD of molasses. Lab-scale digesters were operated in the presence or absence of electrodes, in open (no applied potential) and closed circuit conditions. In the control reactors without electrodes methane production decreased to 50% of the initial rate, while it remained stable in the reactors with electrodes, indicating a stabilizing effect. After 91 days of operation, the now colonized electrodes were introduced in the failing AD reactors to evaluate their remediating capacity. This resulted in an immediate increase in CH4 production and VFA removal. Although a current was generated in the BES operated in closed circuit, no direct effect of applied potential nor current was observed. A high abundance of Methanosaeta was detected on the electrodes, however irrespective of the applied cell potential. This study demonstrated that, in addition to other studies reporting only an increase in methane production, a BES can also remediate AD systems that exhibited process failure. However, the lack of difference between current driven and open circuit systems indicates that the key impact is through biomass retention, rather than electrochemical interaction with the electrodes.
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
authors.forename: Jo
authors.initials: J
authors.lastname: De Vrieze
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Gildemyn
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
authors.forename: Jan B A
authors.initials: JB
authors.lastname: Arends
authors.affiliation: Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland 4072, Australia; Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Inka
authors.initials: I
authors.lastname: Vanwonterghem
authors.affiliation: Department of Materials Science and Engineering, Ghent University, Technologiepark Zwijnaarde 903, B-9052 Zwijnaarde, Belgium.
authors.forename: Kim
authors.initials: K
authors.lastname: Verbeken
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
authors.forename: Nico
authors.initials: N
authors.lastname: Boon
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
authors.forename: Willy
authors.initials: W
authors.lastname: Verstraete
authors.affiliation: Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland 4072, Australia; Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Gene W
authors.initials: GW
authors.lastname: Tyson
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium; Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Hennebel
authors.affiliation: Laboratory of Microbial Ecology & Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium; Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland 4072, Australia. Electronic address: Korneel.Rabaey@UGent.be.
authors.forename: Korneel
authors.initials: K
authors.lastname: Rabaey
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D004560:Electricity; D055664:Electrochemical Techniques; D004566:Electrodes; D008697:Methane / Q000096:biosynthesis; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D018508:Water Purification / Q000379:methods*
chemical_list: D012336:RNA, Ribosomal, 16S; D008697:Methane
keywords: Bioelectrochemical system; Biogas; Methane; Methanosaeta; Methanosarcina