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Natural gas
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Natural gas

Natural gas is a gas produced by the anaerobic decay of organic material. It is usually found in oil fields, but is also generated in swamps and marshes (where it is called swamp gas or marsh gas), in landfill sites, and during digestion in animals (see flatulence).

The primary component of natural gas is methane (CH4), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane (C2H6), propane (C3H8) and butane (C4H10), as well as other gases, in varying amounts. Hydrogen sulphide (H2S) is a common contaminant, which must be removed prior to most uses.

Natural gas is important as a major source for electricity generation through the use of gas turbines and steam turbines. Environmentally, natural gas burns cleaner than other fossil fuels, although it does produce greenhouse gases and is ultimately unsustainable. Its extraction and transportation can generate additional pollution.

The major difficulty in the use of natural gas is transportation. Natural gas pipelines are economical, but are impractical across oceans. Liquefied natural gas tankers are also used, but have higher cost and safety problems. In many cases, as with oil fields in Saudi Arabia, the natural gas which is recovered in the course of recovering petroleum cannot be profitably sold, and is simply burned at the oil field (known as flaring). This wasteful practice is now illegal in many countries, especially since it adds greenhouse gas pollution to the atmosphere, and since a profitable method may be found in the future. The gas is instead re-injected back into the ground for possible later recovery, and to assist oil pumping by keeping underground pressures higher.

Natural gas is often stored as compressed natural gas or CNG, for use in rural homes without connections to pipedd-in public utility services, or with portable grills. CNG (and LPG) is used as a clean alternative to other automobile fuels.

In any form, a strong bad scent (such as ethyl mercaptan) is deliberately added to the otherwise colorless and odorless gas, so that leaks can be detected by the smell before an explosion occurs. In miness, sensors are used and mining apparatus has been specifically developed to avoid ignition sources (e.g. the Davy lamp)

One experimental idea is to use the methane gas that is naturally produced from landfills to supply power to cities. Tests have shown that methane gas could be a financially sustainable power source.

Energy content

Combustion of one hundred cubic feet (1 ccf) of commercial quality natural gas typically yields approximately 1 therm (1000 british thermal units, 30 kWh). One cubic meter yields 38 MJ (10.6 kWh).

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