Comparison of Carbon Dioxide with Anaerobic Digester Biogas as a Methanogenic Biocathode Feedstock

Abstract

BES biogas upgrading studies have typically used bicarbonate or commercial gas mixtures as a biocathode substrate instead of anaerobic digester biogas. Therefore, the objective of this study was to (i) compare the performance of a methanogenic BES between CO 2 -fed and biogas-fed cycles; (ii) investigate possible factors that may account for observed performance differences; and (iii) assess the performance of a biogas-fed biocathode at various applied cathode potentials. The maximum 1-d CH 4 production rate in a biogas-fed biocathode (3003 mmol/m 2 -d) was 350% higher than in a CO 2 -fed biocathode (666 mmol/m 2 -d), and the biogas-fed biocathode was capable of maintaining high performance despite a variable biogas feed composition. Anode oxidation of reduced gases (e.g., CH 4 and H 2 S) from biogas may theoretically contribute 4% to 35% of the total charge transfer from anode to cathode at applied cathode potentials of −0.80 to −0.55 V (vs SHE). The introduction of biogas did not significantly change the biocathode archaeal community (dominated by a Methanobrevibacter sp. phylotype), but the bacterial community shifted away from Bacteroidetes and toward Proteobacteria, which may have contributed to the improved performance of the biogas-fed system. This study shows that anaerobic digester biogas is a promising biocathode feedstock for BES biogas upgrading.

Discovering the Interference of Hydrogen Sulfide on Polyethylenimine-Functionalized Porous Resin for Biogas Upgrading via CO2 Adsorption

“…Aiming at separating CO 2 , various conventional and emerging technologies of biogas upgrading have been widely investigated, such as amine scrubbing, adsorption, membrane separation, cryogenic separation, ionic liquid-based scrubbing, in-situ biogas upgrading by CO 2 -to-CH 4 bioconversion and some hybrid technologies by integrating different methods together. − In addition, recent evidence suggests that some developing materials have also attracted great interest for CO 2 separation from biogas, such as amine-functionalized adsorbents, metal–organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs). , Hereby, amine-functionalized materials as the emerging CO 2 adsorbents exhibit excellent performance on CO 2 capture and separation from typical streams including biogas, flue gas, syngas, and ambient air . Based on the reversible chemical reaction with CO 2 , amine-functionalized adsorbents present high CO 2 selectivity, desirable adsorption capacity, fast kinetics, and facile regeneration with lower energy consumption, which combine the advantages of amine scrubbing and solid adsorption. , Impregnation, grafting, ammoxidation, and direct synthesis are typical approaches for incorporating amine groups into the porous supports to prepare amine-functionalized adsorbents .…”

Insights into the Electron Transfer Behaviors of a Biocathode Regulated by Cathode Potentials in Microbial Electrosynthesis Cells for Biogas Upgrading

“…Proteobacteria, Bacteriodetes, and Firmicutes were the uppermost phyla for all biocathodes (Figure S15e). Normally, Proteobacteria and Bacteriodetes contained amounts of bacteria with extracellular electron transport and hydrolysis function . Firmicutes contained a large amount of hydrogen and acetate production-associated bacteria, and most of them owned the ability to directly accept electrons from the cathode .…”

“…Normally, Proteobacteria and Bacteriodetes contained amounts of bacteria with extracellular electron transport and hydrolysis function. 20 Firmicutes contained a large amount of hydrogen and acetate production-associated bacteria, and most of them owned the ability to directly accept electrons from the cathode. 34 The relative abundance of Firmicutes on Bio-1.0 V was as high as 31.8% compared with 3.3 and 8.6% in Bio-OCP and Bio-0.8 V, respectively.…”

“…Although CH 4 and CO 2 were still detected in the N 2 atmosphere (Figure 3b), it was notable that the amount of CH 4 at OCP was similar to that at −1.0 V when only N 2 was provided (Figure S9), and this indicated that the fermentationinduced CH 4 synthesis rather than CO 2 (released by lysed microbial cell) electromethanogenesis contributed to the observed CH 4 as reported previously. 20,21 Over 88.1% of charges for H 2 generation manifested that H 2 consumption was greatly inhibited (Figure S10). When MES was fed with stock composed of 60% N 2 and 40% CO 2 , the average current density of Bio-1.0 V increased from −7.8 to −9.1 A m −2 (Figure 3a).…”

Natural solar intermittent-powered electromethanogenesis towards green carbon reduction

“…Although the autotrophic process is the main contributor to carbon reduction, yet mixotrophic conditions would benefit from the growth rate especially for the mutual functional microbial communities to promote carbon reduction [12].…”