While the U.S. Environmental Protection Agency (EPA) continues to consider (and inspire much public debate) whether the life-cycle greenhouse gas intensity of renewable corn-based and cellulosic biofuels meet the low-carbon requirements of the Renewable Fuel Standard, the State Department has given the go-ahead to build a pipeline across the U.S.-Canadian border to import much higher carbon petroleum from Canada. On August 20, the U.S. State Department approved the Alberta Clipper Project, an oil pipeline that would deliver petroleum from Alberta, Canada, to refineries in the upper U.S. Midwest. This followed a two-year period of environmental review and public comment.

Canada is the United States' top foreign oil supplier. According to the U.S. Energy Information Agency , 95 percent of Canada’s proven oil reserves are in the form of oil sands. In 2008, the U.S. imported about one million barrels of oil per day from Canada.

Producing oil from tar sands requires a lot more energy and water than producing conventional oil. The oil sands must be strip-mined, transported, and heated to separate the oil from the rock. The process destroys vast tracts of boreal forest and habitat, disrupts migratory paths, and fowls watersheds and airsheds. On September 14, Greenpeace released a report entitled “Dirty Oil: How Tar Sands Are Fueling the Global Climate Crisis.” The report is highly critical of the high carbon-intensity and other harmful environmental impacts of increasing petroleum production from oil sands at a time when the U.S. and Canada should be reducing their carbon footprints, climate impacts, and oil dependence.