What are Tar Sands?
Image © Jiri Rezac / WWF-UK
Tar sands, or oil sands, are deposits of oil found inside a mixture of bitumen, water, sand and clay. They can be strip-mined or deep-mined then refined to produce a usable fuel.
Oil sands or tar sands?
Both terms are technically accurate with the former referring to what the stuff is useful for and the latter describing its raw qualities. Although there is a tendency for the industry and its proponents to use the former term (“those in the business think ‘oil sands’ sounds nicer” [20]) both are widely accepted and understood. We’ve used tar sands in this article to be consistent with work by environmental organisations upon which much of these pages are based [3,9,8].
Strip-mining of tar sands involves the complete removal of large areas of top soil before machinery simply scoops up the sands underneath and transports them away for processing. As many deposits are found deep underground, deep-mining techniques are becoming more prevalent. This utilises a technique called ‘steam-assisted gravity drainage’ by pumping water at 305°C directly into the tar-sands below, turning it into liquid which can then be pumped to the surface. Whilst the strip mining has a has a larger footprint on the landscape, both methods require huge quantities of water and energy in extraction, and both produce a highly impure mixture which is expensive and energy intensive to refine. This energy required for processing is commonly supplied by burning gas or dirty-burning Petroleum coke, a by-product of the refining process[17].
Where are the tar sands?
The Alberta tar sands in North America. (Image: Public domain)
Around 80% of tar sands reserves, and the vast majority of the current industrial operation, are located in Canada’s Alberta province, with the majority of the resource lying in the Athabasca field[18]. The Alberta tar sands hold total reserves of 1350 billion barrels of oil[11]: more oil than has been used in total by humans to-date and more oil than remaining ‘conventional’ sources are estimated to hold. The part of Canada covered by the tar sands is larger than England and Wales combined[21] and the current operations are already the largest single capital project on earth[3].
Why is this happening now?
Tar sands, along with oil shales and heavy oil, are considered an ‘unconventional’ oil – this is to differentiate them from contrast to ‘conventional’ sources of oil which are found inside porous rocks. Unconventional sources of oil like tar sands were often bypassed by major investment due to their high cost of extraction. However, as oil prices have risen higher and the long-term availability of conventional sources has been brought into question, unconventional sources of oil are coming into favour with investors. Furthermore, countries in the rich north, seeing their own supplies in steep decline, are wary of becoming dependent on imports from the Middle East and Russia. Interests in the high-income countries look to Canada’s tar sands to provide an alternative, more politicly comfortable supply of fossil fuels. Canada has already become the largest supplier of oil to the US[3] and total investment is expected to reach £47 billion over the next ten years[1]. As conventional sources dwindle and prices rise, tars sands are expected to continue their astonishing expansion, with output as much as four times 2007 levels by 2020[23] unless alternative action is taken.
Want more?
Read about the local impacts of the tar sands
Read about the global impacts of the tar sands
