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Summer 2013 Vol. 13 Number 1

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Diluted Bitumen

A Crude Oil Like Any Other?

Diluted bitumen is a substance that is often referred to by many names -- dilbit, synbit, tar sands oil. Although it has traveled through pipelines in the U.S. for more than 30 years, few people outside the oil industry had heard of it until recently.

Diluted bitumen is a type of heavy crude oil that is imported from the oil sands region of western Canada. As the name indicates, the substance consists of bitumen -- a dense and viscous form of petroleum -- diluted with lighter oils so it can flow through pipelines. Diluted bitumen is transported through the existing Keystone Pipeline System, and would also be transported through its proposed expansion, the Keystone XL pipeline.

With diluted bitumen imports on the rise, Congress passed legislation in January 2012 calling upon the secretary of transportation to determine whether transporting this heavy crude increases the risk of a pipeline release. The U.S. Department of Transportation asked the National Research Council to convene an expert committee to analyze one aspect of the risk: whether pipelines transporting diluted bitumen have a greater likelihood of accidental release when compared with pipelines transporting other crude oils. The committee was not asked to assess whether the consequences of a diluted bitumen release differ from those of other crude oil releases.

After thorough research of incident statistics, data on the chemical and physical properties, and consultations with experts in pipeline operations and failure mechanisms, the Research Council committee concluded that transporting diluted bitumen through pipelines does not increase the likelihood of release. The study committee took into account many possibilities -- from internal corrosion to operator error to extremes in operating pressures and temperatures -- and found no aspect of diluted bitumen's transport by pipeline makes it more likely than other crude oils to cause an accidental release.

Diluted bitumen does not have physical or chemical properties that are outside the range of other crude oils. Shipments of this substance do not differ from other crudes in flow rate, pressure, or operating temperature. And there is no evidence that pipeline operators manage or maintain their systems any differently when transporting diluted bitumen. In short, diluted bitumen behaves in the pipeline just like other similar crude oils, the committee found.

Though this specific question has been answered, it appears this once obscure form of crude oil will continue to draw attention and is set to remain in the spotlight for the foreseeable future. --  Lorin Hancock

Effects of Diluted Bitumen on Crude Oil Transmission Pipelines: TRB Special Report 311. Committee for a Study of Pipeline Transportation of Diluted Bitumen; Transportation Research Board; Board on Chemical Sciences and Technology, Division on Earth and Life Studies; Board on Energy and Environmental Systems, Division on Engineering and Physical Sciences (2013, approx. 112 pp.; ISBN 978-0-309-28675-6; available from National Academies Press, tel. 1-800-624-6242).

Mark Barteau, DTE Energy Professor of Advanced Energy Research, and director of the Energy Institute, University of Michigan, Ann Arbor, chaired the committee. The study was funded by the Pipeline and Hazardous Materials Safety Administration of the U.S. Department of Transportation.

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Copyright 2013 by the National Academy of Sciences