Gasoline and diesel fuel extracted and refined from Canadian oil sands will release about 20 percent more carbon into the atmosphere over the oil’s lifetime than fuel from conventional crude sources in the Unied States, according to a study by the U.S. Department of Energy’s Argonne National Laboratory; the University of California, Davis; and Stanford University.The researchers used a life-cycle, or “well-to-wheels,” approach, gathering publicly available data on 27 large Canadian oil sands production facilities. The study, published in the journal Environmental Science and Technology, found the additional carbon impact of Canadian oil sands was largely related to the energy required for extraction and refining.