Natural gas provides 24% of our energy. Unlike oil, almost two-thirds of which is imported from foreign sources, our natural gas comes primarily from North America. The annual volume of consumption is projected to rise from 22.5 trillion cubic feet (tcf) in 2009 to about 23.5 tcf in 2030. New activity in Alaska will supply some of that, but most will likely come from the lower 48 states and the Gulf of Mexico. The nation imports less than 3% of its natural gas from outside North America, mostly in the form of liquefied natural gas, or gas cooled to its liquid phase for easier transportation. According to EIA, new estimates of unconventional domestic natural gas sources—primarily in natural gas shales—will result in a marked decrease in imports over the next two decades.
Natural gas is used to heat more than half the homes in the United States.
Global consumption of natural gas in 2006 was 104 tcf. Known world reserves of conventional natural gas total about 6,000 tcf with perhaps another one-tenth of that amount still undiscovered. At that rate, known reserves will be adequate for nearly 60 years. Natural gas shales, a potentially enormous unconventional source of this fossil fuel, could dramatically change this picture. However, estimates regarding the potential of gas shales vary greatly and it is not yet clear how much they will contribute to our supply.
Natural gas is used to heat more than half the homes in the United States and is also a raw material in a variety of common products, such as paints, fertilizers, plastics, medicines, and antifreeze. Propane, which powers many kitchen stoves and outdoor grills as well as home heating systems, is derived from natural gas. Natural gas is also used to generate 21% of our electricity. (See Our Energy System for an overview of how natural gas is used in the United States.)
Natural gas is often described as “clean burning” because it produces fewer undesirable by-products than gasoline. Like all fossil fuels, its combustion emits carbon dioxide, but at about half the rate of coal. In natural gas combined cycle, or NGCC, power plants, we now have technology that takes the waste heat from a natural gas turbine and uses it to power a steam turbine, resulting in a power plant that is as much as 60% efficient.