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Two unconventional sources of oil: oil shales and tar sands

As explained earlier, petroleum under pressure from underground rocks fills pockets in the rocks. But in addition, some muds trap petroleum as they form into shales, resulting in a dense rock filled with oil. The oil is tightly bound within the rock and can be released only if the shale is heated to 900°F. At this temperature, a ton of shale may yield as much as 14 gallons, and three tons of shale would be needed for each barrel of oil. Heating three tons of rock to 900° takes a lot of energy and leaves behind a lot of crushed rock. Much of this rock is obtained from surface mines, and even more energy is needed afterward to restore the damaged land—restore it as much as possible, that is. Not only are oil shales a highly polluting energy source, destructive to the land, but also their net energy yield is low compared to conventional sources of oil.

Tar sands (sometimes also called oil sands) are geologically similar to oil shales, but the petroleum impregnates sand or clay rather than mud. Again, the petroleum is so completely mixed with the inorganic material that one can't pump the oil out. The sand has to be mined, primarily by strip mining, and then washed with hot water. As with oil shales, a mess remains—in this case dirty water as well as tons of sandy rock. Tar sands are said to yield as much as one barrel for about every two tons processed.

Those who believe there is a lot more oil out there than 1–3 trillion barrels are basing their estimates partly on what could be gotten from oil shale and tar sands. An estimated 3 trillion barrels of oil exist in oil shales and about the same in tar sands. Together, these massive but difficult-to-use sources could triple the amount of oil available, if all of it could be recovered.

Much of the world's known tar sands and oil shales are in North America. The United States has two-thirds of the known world oil shale, and it is estimated to contain 2 trillion barrels of oil. Some 90% of U.S. oil shale is in the Green River formation underlying parts of Colorado, Utah, and Wyoming and extends over 17,000 square miles, an area larger than Maryland.23 Canada has an estimated 3 trillion barrels of oil in tar sands, most of it in a single huge area near Alberta now called the Athabasca Oil Sands. Since so much energy is required to get the oil out of these rocks, the net yield would not be nearly as great as from conventional oil wells. Still, the government of Alberta states that tar sands yield six times the amount of energy required to process them.24

Oil shales and tar sands are already causing major environmental controversies, since so much oil exists in them, and since mining and refining it are so polluting. Mining the 2 trillion barrels of petroleum from U.S. oil shales would leave behind 9 trillion tons of waste rock—an amount equal to the weight of 24 million Empire State Buildings. To put this into perspective, in 2007, all the freight transported in the United States weighed 21 billion tons. So it would take all the freight transportation available in the United States about 424 years to move that much waste rock.25

Three tar sands mines are operating today: Suncor (opened in 1967), Syncrude (since 1978), and Muskeg River of Shell Canada (opened in 2003). They are producing 1 million barrels a day26 and have affected 120 square miles.27 Mining Athabasca Oil Sands takes 2.2 to 5 barrels of water for every barrel of oil.28 Water used for this processing comes from the Athabasca River, which starts in the beautiful Canadian Rockies as the outflow from the Athabasca Glacier. The government of Alberta states that only 3% of the average annual outflow of the glacier is required to process the sands,29 but environmental groups estimate that it will require a quarter of Alberta's freshwater.30 This water would end up in holding ponds, contaminated by toxic chemicals from the mining and processing: mercury, arsenic, and a variety of organic compounds that are carcinogenic.31

Effluents from present tar sand operations are being blamed for human and wildlife ailments,32 and the holding ponds present an even greater hazard. According to Professor David Schindler of the University of Alberta, a leading aquatic ecologist, "If any of those tailings ponds were ever to breach and discharge into the river, the world would forever forget about the Exxon Valdez."33

Currently, oil production from Athabasca Oil Sands costs between $15 and $26 a barrel, compared with about $1 per barrel from Saudi Arabia's wells. But when oil prices exceeded $130 a barrel in 2008, mining those tar sands began to sound like economic sense—except for the pollution (at the time of this writing, oil is $72 a barrel).

Oil shales are not yet in commercial development, but Shell Oil Corporation has invested many millions of dollars in attempts to develop this petroleum source.34 The near future will bring a major battle over North American tar sands and oil shales since they offer huge profits at great environmental costs.

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