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Bitumen and Oil Sands

Bitumen is the preferred geologic term for the sticky, highly viscous semi-solid hydrocarbon present in most natural petroleum. It is alternatively called pitch, resin, and asphaltum.

Bitumen is not the same thing as tar, which is a thermo-plastic made by the destructive distillation of coal. Bitumen is a naturally occurring hydrocarbon and has mostly replaced tar as the binding agent in asphalt-based roads. Bitumen generally contains a mixture of large polycyclic aromatic hydrocarbons. The versions of these hydrocarbons present in bitumen are generally extremely large, made up of multiple rings, and have exceptionally low hydrogen to carbon ratios. With liquid hydrocarbons having a ratio of hydrogen to carbon of approximately 2:1, it is easy to see why bitumen with a ratio of 1:2 or 1:3 is so viscous. Bitumen will not flow unless heat or mixed with lighter crudes to reduce viscosity.

Bitumen is exceptionally difficult to extract, with most processes requiring some level of physical mining as opposed to pump extraction. Bitumen crude is found impregnated in sedimentary rock, much of which is located in Canada. This rock is often referred to as “oil sand” or “tar sand.” The Athabasca oil sands are the largest bitumen deposits in Canada. They are only accessible to surface mining. Venezuela and the United States contain the second and third largest deposits of oil sands respectively. Venezuela’s deposits are less viscous and easier to extract, but their technology is behind that of Canada and the United States, so they actually produce less petroleum from their reserves. If all deposits in Canada are upgraded to crude, it is estimated that the country could supply the rest of the world with oil for roughly 200 years.

Transport of bitumen in the form of asphalt for road construction usually occurs at temperatures of 150 C (300 F). Sometimes diesel or kerosene are mixed with asphalt in order to retain liquidity and then separated out immediately before use. In trucks that carry asphalt for road work, all aspects of the vehicle that contain or pump asphalt must be heated. In addition, the nozzles for spraying the asphalt are often flushed with chemicals to dissolve deposits.

Bitumen has been used for a number of purposes over the centuries including as mortar between bricks, base material for statues, as waterproofing, and in roadways. In modern uses, it makes up 5% of the products in asphalt cement used in roadways. Roofing accounts for the majority of the remaining bitumen use, though it has niche applications in sound-deadening materials for computers, dishwashers, and cars. With recent increases in crude oil prices, it has become profitable to upgrade bitumen to synthetic crude.