Developing methane biofiltration In oil sands tailings ponds
Date
2018-09-21
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Abstract
Oil sands tailings ponds in Alberta are mostly anoxic environments estimated to emit 2.7 Mt of CH4 each year to the atmosphere. Because CH4 is 34 times more potent than CO2 as a greenhouse gas, and the government of Alberta has called for a 45% reduction in CH4 emissions by 2020, this release of CH4 has become a pressing issue. One potential way to combat these large fluxes of CH4 from the tailings ponds is via biofiltration. CH4 biofiltration is the process by which aerobic methane-eating or methanotrophic bacteria are used to oxidize CH4 to CO2, a far less potent greenhouse gas. We have tested the potential for biofilters comprised of biochar to be floated on top of the tailings ponds. Experiments conducted in the lab demonstrate that biochar is an excellent matrix to capture and slow the diffusion of CH4 within small volume pores, and in addition acts as a good matrix for growth of methanotrophs. The CH4 oxidation rate in tailings was faster when biochar was added, compared to controls that did not contain any biochar. Furthermore, a mesocosm was designed that mimicked a real-life tailings ponds with CH4 fed from below and O2 from above. After two months of incubation, the mesocosm was able to oxidize CH4 with over 90% efficiency when supplied at a rate higher than the highest CH4 efflux recorded in any tailings pond to date (26 tonnes ha -1y-1). The biofilter was analyzed for its microbial community via sequencing of the 16S rRNA gene. Results revealed a community dominated by various species of methanotrophs, which suggest that it will be robust to environmental fluctuations. The biofilter was also utilized to monitor the co-degradation of naphthenic acids during methanotrophy, and to test the resilience of the biofilter to environmental changes (e.g. in CH4 supply).
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Keywords
Tailings ponds, Biochar, Biofilter
Citation
Zeb, G. (2018). Developing methane biofiltration In oil sands tailings ponds (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/33127