Tar sands or oil sands are a dense mixture of sand, clay, and a viscous form of petroleum known as bitumen. The term “oil shale” applies to various types of rocks which do not technically contain petroleum and often contain no actual shale, despite the name. Both materials can be converted into synthetic crude oil through different processes; tar sands can be refined directly into petroleum products in some cases. The Alberta province of Canada currently produces an equivalent of 1.2 million barrels of oil in bitumen—the majority of which is exported to the United States. Production had been projected by some to more than double by 2015, prior to the recent drop in global oil prices. Oil shale deposits are concentrated in the Green River basin of Colorado, Wyoming, and Utah, but costs and technical barriers have prevented commercial-scale oil shale development to date.
This briefing was the second in a series on alternative transportation fuels. The first briefing focused on liquid coal; future topics include biofuels and electricity.
On May 5, the Environmental and Energy Study Institute (EESI) held a briefing to examine the economic, energy, environmental, and national security issues associated with fuels derived from hydrocarbon deposits known as “tar sands” (the term “oil sands” is also widely used, especially in Canada) and “oil shale.” North America has among the world’s largest concentrations of both of these deposits. Canadian oil sands have already become a significant fuel source, while commercial oil shale development is much less advanced. The future development of these resources face a number of questions regarding production costs, energy inputs, greenhouse gas emissions, and potential impacts on land and water resources. This briefing reviewed the range of costs, benefits, and impacts associated with these fuels, and their implications for policy decisions.
- Tar sands and oil shale are different fossil hydrocarbons from which transportation fuels can be made. The hydrocarbon in oil shale is not oil but a waxy hydrocarbon known as keragen that is rock-like at room temperature. The hydrocarbon in tar sands is a highly viscous hydrocarbon known as bitumen which is semi-solid at room temperature. The term “oil sands” is often used interchangeably with “tar sands”, as the raw material for both is bitumen, but tar is actually derived from man-made processes.
- Alberta oil sands hold the equivalent of more oil than Iraq’s total reserves, and ten times the amount of U.S. reserves. Colorado’s oil shale is estimated to hold over 800 billion barrels’ worth.
- An important difference between oil sands and oil shale is that oil shale must be heated to a much higher temperature (near 900 degrees Fahrenheit) in order to extract and process the hydrocarbon; oil sands will begin to liquefy at approximately 200 degrees Fahrenheit.
- Oil sands and oil shale extraction both require an on-site source of large amounts of energy. One estimate suggested production of one million barrels per day (approximately five percent of U.S. consumption in 2008) would require between seven and 12 full-size conventional power plants—coal or nuclear—to produce electricity or steam for extraction.
- The life-cycle greenhouse gas emissions (GHG) for oil sands and oil shale are significantly greater compared to typical values for conventional oil products--approximately 15 and 50 percent respectively.
- Oil sands and oil shale extraction requires four barrels worth of water for each extracted barrel of fuel. Water availability from the Colorado River would be a significant constraint to oil shale development in the western United States, particularly if future precipitation levels decline as projected. Water quality issues are more dominant for oil sands development; large tailing ponds full of mining refuse have raised concerns about the impacts on the Athabasca River in Alberta.
- Most current oil sands fuel is produced by mining surface deposits with open-pit or strip mining methods, however, only 20 percent of Alberta’s reserves are suited to surface mining. The other 80 percent are deeper “in situ” deposits that require heating with steam or other means to allow pumping liquid material to the surface.
- Open-pit and in-situ extraction of both oil sands and oil shale involve a significant land-clearing and infrastructure footprint that can fragment undisturbed areas. Alberta’s boreal forest provides important habitat for dozens of North American migratory birds, caribou, and other northern wildlife species.
- The energy security benefits of oil sands are significant but should not be overstated. Projected imports of one to three million barrels per day would not be sufficient to eliminate U.S. imports from certain countries of concern, such as Saudi Arabia, Nigeria, or Venezuela.