Advanced Water Management Centre

AWMC Seminar Program: Biochar-mediated Anaerobic Oxidation of Methane

Biochar was recently identified as a useful soil amendment for methane capture. The physical properties of biochar, in terms of surface properties, porosity and adsorptive capacity, provide a favourable 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. It was found that by adding biochar (0.08 g) as the sole electron acceptor in an anoxic environment, CH4 was biologically oxidised, with 8.50 ± 0.41 µmol CO2 produced. 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 incubations with active biochar amendment. Electrochemical characterization revealed that biochar was redox-active with an electron-accepting capacity of up to 0.74 mmol e- g-1, which was similar to the calculated value of 0.85 mmol e- g-1 for the biochar-mediated AOM process. Combined FTIR and XPS analyses demonstrated that the redox activity of biochar relates to its oxygen-based functional groups. Based on microbial community composition as well as intermediates production during incubation, three pathways were proposed for biochar-mediated AOM: 1) direct extracellular electron transfer (DEET) from ANME-2d, 2) indirect extracellular electron transfer (IEET) based on direct interspecies electrical connection between ANME-2d and Geobacter, and 3) IEET based on Geobacter linked to ANME-2d by the metabolite, acetate. Biochar may also facilitate electron transfer from anaerobic methanotrophs to other ubiquitous electron acceptors. We propose that biochar could play a significant role as a direct electron sink for mitigating global CH4 emissions if all globally available biomass-feedstocks were converted to biochar for application to rice paddies and landfill.

AWMC hosts a free seminar every Friday from 9am.

Event Details
Date & Time: 
Friday, 28 June 2019
9am - 10am
Venue: AIBN Building 75, Level 1 Seminar Room
  • Xueqin Zhang

Event Contact: