Grant: Collaborative Research and Development Grants

The main sources of greenhouse gas (GHG) emissions in tailings ponds are from the biodegradation of naphthenic and paraffinic solvents used in bitumen recovery, and to a lesser extent, of residual bitumen. Since CH4 has a global warming potential (GWP) of 28-36 times that of CO2, reducing or eliminating CH4 emissions can be of significant environmental and economic benefit under Alberta's climate change strategy and must be addressed. CH4 is produced from the microbial oxidation of hydrocarbons coupled to the reduction of terminal electron acceptors (TEAs) such as acetic acid or CO2 at low redox conditions (~ -250 mV) when other TEAs such as Fe(III) and sulphate are absent. When such TEAs are present at sufficiently high concentrations, methanogenesis is inhibited. This proposal will examine the impact of different TEA conditions, nutrient amendments and diluent and bitumen concentrations on biogenic gas production in tailings from different types of tailing ponds in laboratory microcosm or bioreactor studies. Rates of biogenic gas production, TEA consumption, and hydrocarbon degradation will be compared to unamended microcosms. The hydrocarbon degraders will be identified and these organisms could potentially be used to enhance degradation rates. Additional studies will evaluate the effect of mass transfer limitation as solvents have to diffuse out of bitumen aggregates to the aqueous phase to be biodegraded. These results will be used to develop a coupled mass transfer and reaction model that would provide basic information on GHG production under a variety of TEAs/redox conditions. It will be used to identify dominant mechanisms and aid in developing strategies to minimize GHG emissions by manipulating pond chemistry. This can have significant environmental and economic benefit to industry under Alberta's climate change strategy and on a wider scale will improve the environment and the quality of life in Canada and globally. The research outcomes may also be applied to other ecosystems such as marine and freshwater sediments to reduce GHG production and further contribute to decrease global warming. This project will also provide training to 10 highly qualified individuals.