The oil derived from Canada's tar sands is more acidic than other forms of petroleum. So does this mean that diluted bitumen (or "dilbit") is more corrosive when flowing through a pipeline? The answer is no, according to the U.S. National Academy of Sciences' National Research Council.
A review of U.S. pipeline ruptures over the last 30 years, along with chemical analyses of the dilbit itself and other factors, show that the tarry stuff is no worse for pipelines than other forms of oil. Or, as chemical engineer Mark Barteau of the University of Michigan put it in the press release announcing the finding: "There's nothing extraordinary about pipeline shipments of diluted bitumen to make them more likely than other crude oils to cause releases."
The key appears to be the fact that the higher total acids in dilbit are not any more corrosive at pipeline operating temperatures of around 65 degrees Celsius, which was also the conclusion of studies by the Albertan government. Dilbit is more corrosive, however, at temperatures above 100 degrees C, the kinds of temperatures found in the refinery where the dilbit presumably ends up.
The finding also only applies to long-distance transportation pipelines, not the kinds of pipelines that carry tar sands oil around the mine or underground melting facilities in Alberta itself. Those pipelines are more susceptible to corrosion and other causes of ruptures thanks, in large part, to the sharp grit still in the tar sands oil at that point. The sand in tar sands wears away wears away the interior walls of these pipelines on a regular basis, so much so that oil sands producers turn the pipelines in place on a regular basis like rotating the tires on a car.
And the finding does not address the question of whether dilbit spills might be worse for the environment than leaks of more conventional crudes. Dilbit has some unique properties that make it more likely to sink in water, among other potential challenges. The residents of Mayflower, Ark. and Kalamazoo, Mich., the locations of major dilbit spills from pipelines, found this out the hard way.
Regardless, the largest environmental problem with tar sands oil isn't ruptures or spills, it's the invisibly accumulating greenhouse gases released during production and when the resulting fuels are burned to move our cars, trucks and airplanes around the world. You can learn more about the problem of this "greenhouse goo" in the July issue of Scientific American. So we can safely move dilbit through pipelines most likely, but to what end?