Description and History
Natural gas is a fossil fuel consisting primarily of methane, a colorless, odorless gas that is burned for electricity or heat. Although natural gas often occurs with petroleum, it has not been used commercially nearly as long as petroleum.
It is inherently more difficult to recover an underground gas vs. liquid. Thus, records of natural gas usage are very sparse before the 19th century. Gas encountered while mining other fossil fuels was either vented or burned in place for safety. In that century, though, a few gas companies emerged in in Europe and North America to tap wells and pipe natural gas short distances for lighting. For a while, electric lighting and gas competed.
With electric lighting spreading at the beginning of the 20th century, the use of natural gas again diminished. But, piping technology improved in the 1920s and especially during World War II. Networks of gas pipes spread after the war within cities and across longer distances. Natural gas began to be a practical energy source for heating and manufacturing, if not illumination.
Mining and Production
Natural gas occurs in pockets above underground oil fields, dissolved within coal seams, and occasionally by itself. In many parts of the world, gas is still simply burned off at the tops of oil derricks. Elsewhere, though, it is immediately separated from any other fossil fuels and treated like the valuable commodity it is.
Natural gas, as recovered, is a mixture. It must be dried, filtered, and separated into components – not just methane, but ethane, propane, and a few heavier organics. Each of these can be sold separately. The methane is also odorized for safety to make gas leaks detectable.
Properties and Uses
Methane is a very clean-burning fuel, though found in shorter supply than either oil or coal. As a gas, it is also more difficult to transport. Natural gas therefore tends to be more expensive than other fossil fuels.
Nevertheless, in regions with well-developed piping systems, gas is the preferred choice for heating and various home appliances. It can be compressed and cooled into a liquid, allowing its transfer by tanker truck or ship over greater distances. Liquid natural gas also powers vehicles such as buses.
Gas can also be used to drive steam turbines for generating electricity. This is relatively more expensive than other methods, so it tends to be kept on standby for meeting peak power needs.
Methane is a useful building block of organic chemistry. As the smallest hydrocarbon, it is the input to much of the plastics industry. It is also important in making hydrogen and ammonia, which lead to further chemistry.