In Alberta, Canada lie vast reserves of bitumen, known as "Tar Sands". Essentially this is shale and sand with a high oil content that can, with a high input of energy, be refined in to liquid oil that can be refined in to petrol, diesel, aviation fuel, gas, etc.
Theoretically, this is an answer to the shortage of oil that North America faces, but it comes at a very high cost. Besides the threat of oil spills, conventional oil production is relatively unobtrusive as it's pumped from vast underground reservoirs. Tar sands however are the complete opposite.
It's like open cast mining on a vast scale. Vast tracts of pristine wilderness disappear, water courses are heavily polluted, there's severe localised air pollution and devastating effects on both wildlife and humans. The energy required to refine tar sands in to oil is immense.
A new film called "Toxic Fuels" is being released on March 15th, supported by The Co-Operative Bank. Have a look at the website here: http://toxicfuels.com/
This is a trailer for the film: