Gas
Gas: Character and Composition
Natural gas is an odourless, colourless, gaseous hydrocarbon mixture made up of methane (CH4) and a small percentage of other light hydrocarbons. Methane is a compound composed of a molecule of one carbon atom and four hydrogen atoms. Small quantities of nitrogen, oxygen, carbon dioxide, sulphur compounds, and water may also be found in "pipeline" natural gas.
How Gas is Formed
Natural gas was formed millions of years ago by the underground decomposition of organic matter, namely dead plants and animals. If the organic matter is buried deeply enough, much of the carbon and hydrogen is converted to methane, the major component of natural gas. Large volumes of methane can be trapped in the subsurface of the earth at places where the right geological conditions occurred at the right times.
Natural gas is found in sandstone, limestone, and other porous rocks beneath the earth’s surface, often in association with crude oil. The heavier hydrocarbons in natural gas can be extracted, through compression or absorption processes, to yield LPG (propane or butane), natural gasoline, and raw materials for petrochemical manufacture.
Use
Because of its high heating value and clean-burning characteristics, natural gas is widely used as a fuel in residential, commercial and industrial applications. It is the dominant energy used for home heating in most of the developed world. In 1998, there were more than 1 million new residential natural gas customers in the US, increasing the nation-wide total to about 56 million homes. The use of natural gas is also widespread in electric power generation and cooling, and as a transportation fuel. Natural gas is the cleanest burning fossil fuel, producing primarily carbon dioxide, water vapour and small amounts of nitrogen oxides. Other fossil fuels are coal and oil.
Measurement
Natural gas is measured and sold in cubic feet (volume) or in British thermal units (heat content). Heat from all energy sources can be measured and converted back and forth between British thermal units (Btu) and metric units.
One Btu is the heat required to raise the temperature of one pound of water one degree Fahrenheit. Ten burning kitchen matches release 10 Btu. One cubic foot of natural gas has about 1031 Btu. A box 10 feet deep, 10 feet long, and 10 feet wide would hold one thousand cubic feet of natural gas. Pipeline companies buy natural gas in thousands of cubic feet or Mcf. M = one thousand.