Does tar sand oil increase the risk of pipeline spills?

Does tar sand oil increase the risk of pipeline spills?

click link

snip

This article originally appeared on Scientific American.


An oil flood through an Arkansas subdivision on March 29 is just the most recent example of pipeline problems in the U.S. In recent weeks, months and years diesel has leaked from a pipeline into wetlands near Salt Lake City; oil has spilled into the Yellowstone River in Montana; and about 20,000 barrels of oil have spewed into the Kalamazoo River in Michigan. The question: Is the problem the pipelines themselves or what they carry?

The answer may be an unfortunate combination of the two. Certainly, the infrastructure has issues. The U.S. is crisscrossed by more than four million kilometers of such pipelines, many decades old. These pipelines spring hundreds of leaks every year, most small. The pipelines can fail for reasons ranging from a backhoe inadvertently striking one to the slow but steady weakening from corrosion. “It’s not a matter of if, but when,” says Susan Connolly, a resident of Marshall, Mich., right near where the Kalamazoo River spill occurred in 2010 as a result of external corrosion.

Critics charge that pipelines carrying diluted bitumen, or “dilbit”—a heavy oil extracted from tar sands mined in northern Alberta—pose a special risk because, compared with more conventional crude, they must operate at higher temperatures, which have been linked to increased corrosion. These pipelines also have to flow at higher pressures that may contribute to rupture as well. Environmental group Natural Resources Defense Council (NRDC) notes that pipelines in the upper Midwest that routinely carry oil from tar sands have spilled 3.6 times more oil per pipeline mile than the U.S. average. The Arkansas and Kalamazoo accidents both involved dilbit.

The chemistry of the tar sands oil could contribute to corrosion as well. In processing, the tar sands are boiled to separate the bitumen from the surrounding sand and water, and then mixed with diluent—light hydrocarbons produced along with natural gas—to make the oil less viscous and able to flow. But even so, the resulting dilbit is among the lowest in hydrogen as well as the most viscous, sulfurous and acidic form of oil produced today.