title: Evaluation of gas and carbon transport in a methanogenic bioelectrochemical system (BES).
abstract: Bioelectrochemical systems (BESs) may be used to upgrade anaerobic digester biogas by directly converting CO2to CH4. The objective of this study was to evaluate gas (N2, CO2, CH4, and H2) and carbon transport within a methanogenic BES. Four BES configurations were evaluated: abiotic anode with abiotic cathode (AAn-ACa), bioanode with abiotic cathode (BAn-ACa), abiotic anode with biocathode (AAn-BCa), and bioanode with biocathode (BAn-BCa). Transport of N2, a gas commonly used for flushing anoxic systems, out of the anode headspace ranged from 3.7 to 6.2 L/d-atm-m2, normalized to the proton exchange membrane (PEM) surface area and net driving pressure (NDP). CO2was transported from the cathode to the anode headspace at rates from 3.7 to 5.4 L/d-atm-m2. The flux of H2from cathode to anode headspace was 48% greater when the system had a biocathode (AAn-BCa) than when H2was produced at an abiotic cathode (BAn-ACa), even though the abiotic cathode headspace had 75% more H2than the AAn-BCa biocathode at the end of 1 day. A 7-day carbon balance of a batch-fed BAn-BCa BES showed transient microbial carbon storage and a net transport of carbon from anode to cathode. After a 7-day batch incubation, the CH4production in the biocathode was 27% greater on a molar basis than the initial CO2supplied to the biocathode headspace, indicating conversion of CO2produced in the anode. This research expands the current understanding of methanogenic BES operation, which may be used in improving the assessment of BES performance and/or in the development of alternative BES designs and mathematical models. Biotechnol. Bioeng. 2017;114: 961-969. © 2016 Wiley Periodicals, Inc.
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia, 30332-0512.
authors.forename: Christy M
authors.initials: CM
authors.lastname: Dykstra
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia, 30332-0512.
authors.forename: Spyros G
authors.initials: SG
authors.lastname: Pavlostathis
mesh_terms: D001674:Bioelectric Energy Sources; D056804:Biofuels; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D004566:Electrodes; D008697:Methane / Q000032:analysis / Q000378:metabolism*
chemical_list: D056804:Biofuels; D002245:Carbon Dioxide; D008697:Methane
keywords: bioelectrochemical system; biogas upgrading; carbon dioxide; mass transport; methane