Blogs & Comment

Diluted bitumen: the key sticking point for Keystone XL?

Concerns about dilbit.

Reports that the rupture of an Exxon pipeline in Arkansas carrying Canadian heavy crude have “sunk” the Keystone’s chances are, as they say, grossly exaggerated. A Pew poll predating the accident showed that 66 per cent of Americans support TransCanada’s project to link Canada’s oilsands to Texas refineries and, I argued earlier this week, there’s no reason why they should change their minds.

The accident, though, will likely shift the U.S. debate over Keystone away from whether or not building the pipeline would have any significant impact on greenhouse gases (the U.S. State Department says it won’t, environmentalists disagree), to whether or not Western Canada’s oil is a particularly hazardous fuel. The array of claims around Alberta’s crude is wide and varied: on the one hand, anti-Keystone groups contend that dilbit — i.e. diluted bitumen, thick oilsand crude mixed with light hydrocarbons that will allow it to flow through a pipeline — is more corrosive than other types of oil and sinks in water rather than floating, which makes it harder to clean rivers and lakes after a spill. On the other hand, TransCanada maintains that “oil is oil,” as spokesperson Shawn Howard wrote in an email pointing to a wealth of studies in both Canada and the U.S. that found no evidence dilbit is more corrosive than other heavy crude oils. Also, according to information posted on TransCanada’s website, dilbit floats in clear water, though it will sink if it becomes mixed with dirt or in turbulent waters, like any other crude. The American Petroleum Institute has come to similar conclusions.

So, which is it? U.S.-based pipeline safety consultant Richard Kuprewicz offered a more nuanced take. Dilbit can carry a higher risk of corrosion, but only if the pipeline is operating “at a higher temperature,” Kuprewicz, president of Accufacts Inc., wrote in an email exchange. It’s also important to note that “dilbit” is a catch-all term for diluted bitumen mixtures whose composition varies based on the quality of the oilsand crude itself as well as chemicals used by producers to dilute it (the mix is generally a trade secret). “Slight composition changes in the bitumen and/or the dilbit can change the viscosity and or the gravity,” said Kuprewicz, leading to “severe” pressure fluctuations that can quickly lead to a rupture in pipelines with cracking risks. (TransCanada, for its part, uses strict quality control to minimize differences among dilbit batches it receives from producers, according to Howard.)  That said, modern steel pipelines are much better equipped than older pipelines to avoid such failures, Kuprewicz added.

Stressing that diluted bitumen doesn’t behave exactly the same as other convention heavy crude oils, Kuprewicz also said that an oil spill response “may have to be considerably different for dilbit.”

The definitive answer on Canada’s watered-down bitumen will likely come in this summer when a Congressionally mandated National Academies of Sciences (NAS) study on the risks of piping oilsand crude is due out. The NAS is charged with suggesting new pipeline regulations if it deems current safety requirements inadequate.

The Exxon spill could very well make that report a key determinant of the White House’s stance on Keystone. And that, in turn, would considerably delay an approval, especially if NAS recommends new rules — which might or might not be essentially the same as the 57 safety specifications above the federal standard to which TransCanada has already agreed.

One thing is for sure, an open and transparent study should at least put the dilbit question to rest once and for all.

Erica Alini is a California-based reporter and a regular contributor to, where she covers the U.S. economy. Follow her on Twitter: @ealini.