Demonstrators protest the Keystone XL Pipeline in 2011. (AP Photo/Evan Vucci.)
When the Exxon Pegasus pipeline ruptured Friday in Mayflower, Arkansas, tens of thousands of gallons of diluted bitumen were sent forth into a residential neighborhood, and 22 homes had to be evacuated. Since this is the same sort of oil that would be carried by the Keystone XL pipeline, were it to be built, the Arkansas spill is appropriately spurring a conversation about safety. Is Keystone also going to lead to more spills? (There have been twelve on the completed portions of the pipeline already.) And how dangerous is this stuff spilling all over the ground?
But this conversation must start with a simple fact: There are too many known unknowns about diluted bitumen. We don't know exactly what's in it, and the government hasn't fully studied how safe it is to transport.
Bitumen is a form of petroleum that occurs in a solid, or semi-solid, state: It can be sludgy or even be brittle, like rocks. That’s what is buried deep in the Canadian oil sands. In order to transport this bitumen through thousands of miles of pipelines so that it can be refined, it has to first be diluted, so it flows like a liquid.
That diluent is usually a natural gas liquid—but we don’t know for certain what it is. The industry considers its diluent formulas proprietary information and won’t share it with regulators.
When the State Department released its first Environmental Impact Statement on Keystone XL, the EPA gave it an “inadequate” rating in part because it didn’t have any specific information on diluents. “We believe an analysis of potential diluents is important to establish the potential health and environmental impacts of any spilled oil, and responder/worker safety, and to develop response strategies,” the EPA said at the time.
Yet, the second and final Enviromental Impact Statement of Keystone XL released recently by the State Department still had no specific information on dilbit diluents, and evaded the question with some generalities:
The exact composition of the dilbit is not publicly available because the particular type of bitumen and diluents blend produced is variable and is typically a trade secret. The bitumen diluent mixture with bitumen from the oil sands is generally similar to heavy sour crude. […]
Although reported information on dilbit releases is scarce in the literature, once diluents and bitumen are mixed together to form dilbit, they behave as a conventional crude oil. Therefore, this assessment has focused on the impact of crude oil in general, but when applicable, evaluated the specific characteristics (i.e. viscosity) of dilbit. The degree of impact can vary depending on the cause, size, type, volume, location, season, environmental conditions, and the timing and degree of response actions.