Natural Gas

Basics

Natural gas, a fossil fuel comprised mostly of methane, can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) to fuel cars and trucks.

(LNG) is natural gas that has been cooled to about -260°F for shipment and/or storage as a liquid. In this compact form, natural gas can be shipped in special tankers to receiving terminals in the United States and other importing countries.

Hydraulic fracturing of shale rock formations is a new technology used to extract natural gas by pumping liquids under high pressure into a well to fracture the rock and allow gas to escape from tiny pockets in the rock.

Natural-gas-fueled power plants basically involves three main sections. The compressor, which draws air into the engine, pressurizes it, and feeds it to the combustion chamber at speeds of hundreds of miles per hour. The combustion system injects a steady stream of fuel into combustion chambers where it mixes with the air. The combustion produces a high temperature, high pressure gas stream that enters and expands through the turbine section, which spins the rotating blades. A recuperator often captures waste heat in the turbine exhaust system to preheat the compressor discharge air before it enters the combustion chamber.

Power plants use several methods to convert gas to electricity. One method is to burn the gas in a boiler to produce steam, which is then used by a steam turbine to generate electricity. A more common approach is to burn the gas in a combustion turbine to generate electricity. Another technology is called “combined cycle” and achieves a higher efficiency by using the same fuel source twice.

Opportunities

• Nearly 87% of U.S. natural gas used is domestically produced. Some is imported from Canada and shipped to the United States in pipelines.
• Hydraulic fracturing is a new technique used in conjunction with horizontal drilling, which enables gas producers to extract shale gas economically and has greatly reduced the amount of area that has to be disturbed to produce each cubic foot of natural gas.
• Its abundance and ease of extraction in the U.S. makes it inexpensive.
• We can also use machines called “digesters” that turn today’s organic material into natural gas. This process replaces waiting for millions of years for the gas to form naturally.
• It can be used to power vehicles.
• It emits 60-90% less smog-producing pollutants than other fossil fuels.
• Natural gas emits 30-40% less greenhouse gas emissions than other fossil fuels.

Challenges

• Natural gas is a nonrenewable resource.
• Natural gas is made up mostly of methane, which is a very potent greenhouse gas. Some methane leaks into the atmosphere from coalmines, oil and gas wells, and natural gas storage tanks, pipelines, and processing plants.
• The process of extraction, treatment, and transport of the natural gas to the power plant generates additional emissions.
• Without using controversial hydraulic fracturing techniques, natural gas does not flow to the well rapidly, and commercial quantities cannot be produced economically.
• The fracturing of wells requires large amounts of water. In some areas of the country, significant use of water for shale gas production may affect the availability of water for other uses, and can affect aquatic habitats. Hydrofracturing also produces large amounts of wastewater, which may contain dissolved chemicals and other contaminants that require treatment before disposal or reuse.
• The injection of wastewater into the subsurface can cause earthquakes that are large enough to be felt and may cause damage.

Future Trends

U.S. natural gas production and consumption were nearly in balance through 1986. After that, consumption began to outpace production, and imports of natural gas rose to meet U.S. demand for the fuel. Production increased from 2006 through 2010, when it reached the highest recorded annual total since 1973. The increases in production were the result of more efficient, cost-effective drilling techniques, notably in the production of natural gas from shale formations.

Texas’ natural gas marketed production was 30% as of 2010.

About 25% of energy used in the United States came from natural gas in 2010. The United States used 24.64 trillion cubic feet (Tcf) of natural gas in 2010.