Every day more than one million barrels of oil flow to refineries in the United States from western Canada’s oil sands region. Producers hope to quadruple that amount in the next decade, arguing that oil from a friendly neighbor will deliver an extra degree of national security.
But this oil is no ordinary crude oil, and it carries with it risks that we’re only beginning to understand. Its core ingredient — bitumen — is not pumped from wells but is strip-mined or boiled loose underground.