Understanding the biological processes of oil sands’ tailings ponds could lead to lower greenhouse gas emissions
In the Athabasca oil sands region of northeastern Alberta, an estimated 170 billion barrels of crude oil lie beneath 75,000 square kilometres of forest — about 20 percent of which is close enough to the surface to allow extraction, typically through a hot-water process.
Commercial mining began here in 1967 and as bitumen recovery has increased, so too has extraction waste, which is stored in settling areas called tailings ponds. Daily production of 1.2 million barrels of crude oil creates 500,000 cubic metres of waste — a mix of water, sand, clay, toxic compounds, and residual bitumen that releases greenhouse gases into the atmosphere.
To stop the expansion of tailings ponds, which now span 176 square kilometres, oil companies are testing and using mechanical and chemical ways of accelerating the settling process and, by extension, the eventual land reclamation. Academic researchers, meanwhile, co-led by Dr. Gerrit Voordouw of the University of Calgary and Dr. Julia Foght of the University of Alberta, are looking to genomics for biological solutions to tailings ponds, as well as pipeline corrosion and reservoir souring.
Over the past four years, the scientists have analyzed 250 samples collected by four companies from eight tailings ponds. From the DNA of millions of microbes, they have generated genomic profiles of the ponds’ whole microbial communities. These revealed that each pond has a unique community of naturally occurring bacteria, but the predominant microorganisms are similar and they have common biological processes.
By understanding these processes, the researchers aim to harness the genetic potential of tailings ponds’ microbes to decrease the water and land they use, as well as their greenhouse gas emissions. They now know, for example, that organisms called methanotrophs are oxidizing 20 to 40 percent of methane in the top layer of many ponds, naturally reducing emissions. “Going forward, we’d like to improve that ratio,” says Dr. Voordouw.
Documenting activities in these microbial communities has already allowed the researchers to assure an oil company that it was safe to begin closing one of its tailings ponds.
Suncor’s senior scientist, Dr. Joseph Fournier, says such research is “absolutely beneficial” to the oil industry. As an example, Dr. Fournier says, Dr. Voordouw’s team “brought to our attention that sulfide production was well advanced in the ponds, more so than anticipated. Having that awareness allowed us to do further work in preparation for risk reduction.”
