Biochar-Mediated Anaerobic Oxidation of Methane

Abstract

Biochar was recently identified as an effective soil amendment for CH4 capture. Corresponding mechanisms are currently recognized to be from physical properties of biochar, providing a favorable growth environment for aerobic methanotrophs which perform aerobic methane (CH4) oxidation. However, our study shows that the chemical reactivity of biochar can also stimulate anaerobic oxidation of CH4 (AOM) by anaerobic methanotrophic archaea (ANME) of ANME-2d, which proposes another plausible mechanism for CH4 mitigation by biochar amendment in anaerobic environments. It was found that, by adding biochar as the sole electron acceptor in an anaerobic environment, CH4 was biologically oxidized, with CO2 production of 106.3 ± 5.1 μmol g–1 biochar. In contrast, limited CO2 production was observed with chemically reduced biochar amendment. This biological nature of the process was confirmed by mcr gene transcript abundance as well as sustained dominance of ANME-2d in the microbial community during microbial incubations with active biochar amendment. Combined FTIR and XPS analyses demonstrated that the redox activity of biochar is related to its oxygen-based functional groups. On the basis of microbial community evolution as well as intermediate production during incubation, different pathways in terms of direct or indirect interactions between ANME-2d and biochar were proposed for biochar-mediated AOM.

Enhancing methane oxidation in a bioelectrochemical membrane reactor using a soluble electron mediator

“…Coulombic efficiency estimation showed that only 54.3% of electron recovery can be obtained against the assumption that the current output in this period was solely driven by AOM (Additional file 1: Table S1), which suggests that there was some other more oxidized carbonaceous substances contributed to the current output. This could be ascribed to the oxidation of intracellular storage substances present in methanotrophic biomass providing additional reducing equivalents, as previously discussed [30,31]. Afterwards, the current in the BEMR stabilized at around 149 mA m -2 when the HFMs was pressurized at 0.8 bar.…”

“…Methanoperedens was the only candidate being responsible for CH 4 activation. Interestingly, organisms belonging to the genus Geobacter were also observed in the community enriched in BEMR, reaching a relative abundance of 2.4%, which could be stimulated by readily available intermediates (such as acetate) released by intracellular storage substances of methanotrophic biomass [30,31]. Regarding the Control-BES, the microbial community was also consistent with the inoculum when nitrate was fed in the first 147 days.…”

Microbial niche nexus sustaining biological wastewater treatment

“…Materials on which biofilms attach may additionally affect microbial niches. Functional groups on the surface of materials can change the redox activities, benefiting some bacteria suitable for the specialized redox environment as well as affecting their metabolisms 36 . For example, bacteria with the DIET ability may need to initially produce conductive pili and other biological electrical connections, which make them grow slower.…”

A Structured Approach for the Mitigation of Natural Methane Emissions—Lessons Learned from Anthropogenic Emissions

“…Examples for in-situ mitigation are thus the collection and technical oxidation of landfill gas but the oxidation by methanotrophs in biotic covers of the landfill [109]. Methane emissions from soils can be reduced by supporting aeration of the soil and by creating a favorable growth environment for methanotrophs, for example, by adding biochar, but also other materials such as sand, slag, sludge, compost or wood pellets [151].…”