unconventional oil

Heavy oils, in abundant supply, are no doubt going to make up a large part of our oil consumption in the not so far future. They are very hard to produce, and generally require heat to mobilize the sticky, tar-like substance. The most commonly used method is steam flooding, where steam is injected into the oil reservoir. But it takes energy to create the steam, which is typically produced by burning gas. Voila: a large carbon footprint.