It's hard to imagine a source of energy that is even dirtier than oil, but in fact there is: tar sands.

President Obama in an early visit to Canada (now the leading exporter of oil to the U.S.) has both environmentalists and oil executives wondering and worrying about what he is going to say in regards to the expanding tar sands operation in northern Alberta when he arrives on Thursday. Some call the tar sands operation a "pillar" of North American energy independence, an oil reserve second only to Saudi Arabia. But many scientists doubt the continued feasibility of the operation saying it might it be "the greatest environmental disaster in human civilization." 

Extracting bitumen, the tar-like substance found deep underneath a region famous for its pristine arboreal forest, is a complex and energy-intensive process, requiring enormous quantities of fresh water and deforestation. The region affected is approximately the size of Florida (140,000 square km), and though a great deal of bitumen is locked in the sands, only about 10 percdent (an estimated 174 billion barrels) can be extracted in total.  And with that extraction comes devastating environmental impacts.

First off, the tar sands process requires a total clearcut of the forest. That in itself causes an enormous amount of CO2 to be released into the atmosphere. The tar sands are now the second-largest cause of global deforestation after Brazil (which is primarily cutting down its forests to produce biodiesel crops), and the fastest-growing cause of greenhouse gas emissions in Canada.

Then begins the excavation and processing. Compared to surface mining for tar-soaked sand, drilling for oil looks almost "eco-friendly." Once hauled to the surface, the process of extracting the bitumen requires a great deal of energy in the form of natural gas, approximately 1200 BTU's for every 6000 BTU's created in a process called "hydrocracking," which sounds hi-tech, but is more or less the same steam-driven process invented in the early 20th century.

That brings us to the water. For every gallon of oil extracted, 3-5 gallons of water are required in the process. This will mean diverting more than 7 percent of Canada's fresh water supply to the oil and gas industry. When the water has done its job, it is dumped into tailings ponds loaded with toxic chemicals and heavy metals. Canada has very poor standards when it comes to preserving water quality, and many tests have shown that toxicity levels dramatically rise in the water table, causing increased rates of cancer in neighboring regions.

None of these more obvious impacts, and other impacts like soil erosion, endangered wildlife, ecosystem stability and long-term impacts on human health are factored into the cost of tar sand oil. So for this reason, Forest Ethics in conjunction with two Native Tribes in the region, have taken out full page ads in USA Today this week (right).

As Chief Allan Adam of the Athabasca Chipewyan First Nation said:

"Both the federal and provincial governments have failed our aboriginal community for the sake of money, for the sake of corporate interests, and for the sake of increasing energy exports to the United States. We are seeing disheartening toxicity levels in our animal life and have now received confirmation of unacceptable cancer rates to people in our community.  As a people who have been here for thousands of years, we are sad that no one will listen and that government sits back and issues denials and publicity campaigns without substance."

Forest Ethics is currently running a petition to Barack Obama and Canada's Prime Minister Stephen Harper. You can sign it here.

To learn more about the Alberta Tar Sands, I highly encourage the in-depth report written by Don Woynillowicz of World Watch Institute.