Oil shale, a fine-grained sedimentary rock, contains significant amounts of kerogen (a solid mixture of organic chemical compounds), from which one can extract liquid hydrocarbons. The name oil shale has been described as a promotional misnomer, since the rock is not necessarily a shale and its kerogen is not crude oil; it requires more processing than crude oil, which affects its economic viability as a crude oil substitute.[1][2] Deposits of oil shale are located around the world, including major deposits in the United States. Global deposits are estimated as equivalent to 2.8 trillion to 3.3 trillion barrels (450×109 to 520×109 m3) of recoverable oil.[2][3][4][5]
The chemical process of pyrolysis can convert the kerogen in oil shale into synthetic crude oil. When heated to a sufficiently high temperature a vapor is driven off which can be distilled (retorted) to yield a petroleum-like shale oil—a form of non-conventional oil—and combustible shale gas (shale gas can also refer to gas occurring naturally in shales). Oil shale can also be burnt directly as a low-grade fuel for power generation and heating purposes, and can be used as a raw material in the chemical and construction materials industries.[6][2]
Oil shale has gained attention as an energy resource as the price of conventional sources of petroleum has risen, and as a way for some areas to secure independence from external suppliers of energy.[7][8] The oil shale industry is well-established in Estonia, China, and Brazil, and the United States is taking steps in that direction. At the same time oil shale mining and processing involves a number of environmental issues, such as land use, waste disposal, water use and waste water management, and air pollution.[9][10] The industry has foundered in Australia due to its opposition on these grounds.
