The oil that would flow through the pipeline is known as diluted bitumen, or dilbit, and it has become a lighting rod for controversy in the debate over the pipeline, which would send as much as 830,000 barrels every day from the tar sands of Alberta, Canada to refineries as far as Texas. The pipeline would cross six states, sometimes passing through environmentally sensitive terrain where spills would be of special concern.
While bitumen has long been refined into oil, regulation of diluted bitumen has been slow to follow. Federal safety officials, for example, don't know precisely which chemicals shippers mix with bitumen to create dilbit. And even industry groups can't say exactly how corrosive dilbit is. Research is spotty and outdated; there have been no independent scientific studies exploring the relationship between dilbit and pipeline corrosion.
Here's a primer on what is—and isn't—known about dilbit.
What Exactly Is Diluted Bitumen, or Dilbit?
Bitumen is a tar-like type of petroleum that is a byproduct of the oil refining process as well as a naturally occurring substance found in the oil sands of Canada, Venezuela, the United States and other countries. These sands are considered unconventional deposits, meaning that the petroleum doesn't come from the oil wells that have traditionally supplied most of the world's crude. Instead tar sands deposits are mined, usually using strip mining or open pit techniques. The oil can also be extracted by underground heating. In recent years the combination of high oil prices and new technology has made harvesting bitumen extremely profitable. Analysts forecast that capital investment in the oil sands market will reach $45 billion over the next decade.
In its natural state, bitumen is extremely viscous and flows very slowly. To move it through pipelines, oil companies dilute it with chemicals called hydrocarbons to create diluted bitumen, or dilbit. The exact composition and quantity of these hydrocarbons—collectively called diluents—is considered proprietary information and is not shared with regulators.
The bitumen itself contains many of the same chemicals found in regular crude oils, said Carl Weimer, executive director of the independent, non-partisan Pipeline Safety Trust. But he said there are a lot of unanswered questions about the nature of the chemicals added to bitumen to make dilbit. "I think everybody has a good sense of the tar sands itself ... but the diluents used to move it through the pipeline is a whole separate issue."
While the Keystone project has focused the public's attention on Canadian bitumen, plans are also under way to mine bitumen in Utah.
Why Are People Worried?
Multiple reports of ruptures in pipelines that carry dilbit have raised concerns about its safety. Most dramatic was the July 2010 Enbridge Energy pipeline leak, which dumped 843,000 gallons of dilbit into the Kalamazoo River. The cleanup operation has so far involved more than 2,000 personnel, 150,000 feet of boom, 175 heavy spill response trucks, 43 boats and 48 oil skimmers. The cost is expected to exceed $700 million.