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Combustion of oil shale
Oil shale is a fine-grained sedimentary rock containing significant amounts of kerogen, from which one can extract liquid hydrocarbons. 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 of recoverable oil. 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 to yield a petroleum-like shale oil—a form of non-conventional oil—and combustible shale gas. 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. 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. 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. The industry has foundered in Australia due to its opposition on these grounds. (more...)

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Human respiratory system

A diagram of the human respiratory system, which consists of the airways, the lungs, and the respiratory muscles that mediate the movement of air into and out of the body. Within the alveolar system of the lungs, molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous environment and the blood. Thus, the respiratory system facilitates oxygenation of the blood with a concomitant removal of carbon dioxide and other gaseous metabolic wastes from the circulation.

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