Natural gas is a mixture of combustible gases formed underground by the decomposition of organic materials in plant and animal. It is usually found in areas where oil is present, although there are several large underground reservoirs of natural gas where there is little or no oil. Natural gas is widely used for heating and cooking, as well as for a variety of industrial applications.
Natural gas was known to early man in the form of seepages from rocks and springs. Sometimes, lightning or other sources of ignition would cause these gas seepages to burn, giving rise to stories of fire issuing from the ground. In about 900 B.C. natural gas was drawn from wells in China. The gas was burned, and the heat was used to evaporate seawater in order to produce salt. By the first century, the Chinese had developed more advanced techniques for tapping underground reservoirs of natural gas, which allowed them to drill wells as deep as 4,800 ft (1,460 m) in soft soil. They used metal drilling bits inserted through sections of hollowed-out bamboo pipes to reach the gas and bring it to the surface.
The Romans also knew about natural gas, and Julius Caesar was supposed to have witnessed a "burning spring" near Grenoble, France. Religious temples in early Russia were built around places where burning natural gas seepages formed "eternal flames."
In the United States, the first intentional use of natural gas occurred in 1821 when William Hart drilled a well to tap a shallow gas pocket along the bank of Canadaway Creek near Fredonia, New York. He piped the gas through hollowed logs to a nearby building where he burned it for illumination. In 1865, the Fredonia Gas, Light, and Waterworks Company became the first natural gas company in the United States. The first long-distance gas pipeline ran 25 mi (40 km) from a gas field to Rochester, New York, in 1872. It too used hollowed logs for pipes. The development of the Bunsen burner by Robert Bunsen in 1885 led to an interest in using natural gas as a source of heating and cooking, in addition to its use for lighting. In 1891, a high-pressure gas deposit was tapped in central Indiana, and a 120 mi (192 km) pipeline was built to bring the gas to Chicago, Illinois.
Despite these early efforts, the lack of a good distribution system for natural gas limited its use to local areas where the gas was found. Most of the gas that came to the surface as part of oil drilling in more remote areas was simply vented to the atmosphere or burned off in giant flares that illuminated the oil fields day and night. By the 1910s, oil companies realized that this practice was costing them potential profits and they began an aggressive program to install gas pipelines to large metropolitan areas across the United States. It wasn't until after World War II that this pipeline program had reached enough cities and towns to make natural gas an attractive alternative to electricity and coal.
By 2000, there were over 600 natural gas processing plants in the United States connected to more than 300,000 mi (480,000 km) of main transportation pipelines. Worldwide, there are also significant deposits of natural gas in the former Soviet Union, Canada, China, and the Arabian Gulf countries of the Middle East.
Raw natural gas is composed of several gases. The main component is methane. Other components include ethane, propane, butane, and many other combustible hydrocarbons. Raw natural gas may also contain water vapor, hydrogen sulfide, carbon dioxide, nitrogen, and helium.
During processing, many of these components may be removed. Some—such as ethane, propane, butane, hydrogen sulfide, and helium—may be partially or completely removed to be processed and sold as separate commodities. Other components—such as water vapor, carbon dioxide, and nitrogen—may be removed to improve the quality of the natural gas or to make it easier to move the gas over great distances through pipelines.
The resulting processed natural gas contains mostly methane and ethane, although there is no such thing as a "typical" natural gas. Certain other components may be added to the processed gas to give it special qualities. For example, a chemical known as mercaptan is added to give the gas a distinctive odor that warns people of a leak.
The methods used to extract, process, transport, store, and distribute natural gas depend on the location and composition of the raw gas and the location and application of the gas by the end users. Here is a typical sequence of operations used to produce natural gas for home heating and cooking use.
Natural gas burns readily in air and can explode violently if a large quantity is suddenly ignited. Entire buildings have been leveled by powerful blasts resulting from natural gas leaks. In other cases, people have suffocated in closed rooms that slowly filled with natural gas. Because natural gas is odorless, foul-smelling mercaptan is added to the gas so that even a small leak will be immediately noticeable. To protect high-pressure underground gas pipelines, a bright yellow plastic tape is buried in the ground a few feet above the pipeline to warn people who might be digging in the area. That way, they will uncover the tape before they actually strike the pipeline below. Warning signs are also placed at ground level along the entire length of the pipeline as an additional precaution.
Because natural gas is clean burning, it is being considered as an alternative fuel for motor vehicles. Compressed natural gas (CNG) cars and trucks are already on the road in many areas. Companies using industrial processes that require high temperatures are also turning to natural gas instead of other fuels in order to reduce the air pollution emitted by their plants. This includes companies involved in manufacturing steel, glass, ceramics, cement, paper, chemicals, aluminum, and processed foods.
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Tussing, Arlon R., and Bob Tippee. The Natural Gas Industry: Evolution, Structure, and Economics. 2nd ed. Tulsa, OK: PennWell Publishing, 1995.
Natural Gas Information and Educational Resources. http://www.naturalgas.org (November 1, 2000).
Pacific Gas and Electric Company. "How Our Gas System Works." http://www.pge.com/006_news/006c2gassys.shtml (November 12, 2000).
— Chris Cavette