Natural gas is a fossil fuel composed almost entirely of methane, but does contain small amounts of other gases, including ethane, propane, butane and pentane. Methane is composed of a molecule of one carbon atom and four hydrogen atoms.
Natural gas is used extensively in residential, commercial and industrial applications.
It is the dominant energy used for home heating with with about 55 percent of American homes using gas. In 1998, there were more than 1 million new residential natural gas customers, increasing the nationwide total to about 56 million homes. The use of natural gas is also rapidly increasing in electric power generation and cooling, and as a transportation fuel. Natural gas is the cleanest burning fossil fuel, producing primarily carbon dioxide, water vapor and small amounts of nitrogen oxides. Other fossil fuels are coal and oil, which together with natural gas, account for about 88 percent of U.S. energy consumption.