The oil sands — a growing source of U.S. supply — have long been in environmentalists’ crosshairs over their emissions and the impact of extraction projects on Canada’s boreal forests.
Two environmental groups — the Sierra Club and the Southern Alliance for Clean Energy — in June sued the Pentagon for violating the 2007 law by purchasing fuel from refineries that process oil sands.
But Graham came away from the mid-September visit to Canada impressed by the projects and accused environmentalists of overstating the ecological footprint of oil sands, which are a large energy source in the hands of a U.S. ally.
Oil sands bring higher carbon emissions than many other grades of oil, but exactly how much more has been disputed for years and depends on what phases of the fuel cycle are analyzed.
The energy-intensive production of oil sands — which must be separated from clay, water and sand — belches far more carbon than producing conventional oil.
But the difference shrinks when other phases of fuel development and use are thrown into the equation.
A recent study by the prominent industry consulting firm Cambridge Energy Research Associates concluded that oil sands result in emissions that are, on average, 6 percent higher than the average crude oil used in the U.S. The figure is based on a so-called lifecycle analysis, which considers production, transport, refining and use in engines.