How is Natural Gas Produced?
Across the world, the majority of the natural gas is produced in the major oil producing countries like Qatar, the United States, Australia, and Russia. These countries export Natural Gas (in liquified form at -260 Deg. F), to other countries. Natural gas is primarily made up of methane, with low concentrations of other hydrocarbons, water, carbon dioxide, nitrogen, oxygen, and some sulfur compounds.
Production Methods:
1] Conventional Natural Gas Production
Natural gas is extracted from subsurface rock formations via drilling. Advances in hydraulic fracturing technologies have enabled access to large volumes of natural gas from shale.
The vast majority of natural gas in the world is considered a fossil fuel because it is made from sources formed over millions of years by the action of heat and pressure on organic materials. Conventional natural gas is found in subsurface rock formations and is extracted through a well drilled into that formation. In recent years, an increasingly large proportion of domestic natural gas is produced from low-permeability formations, such as shale. Extracting natural gas from these tight formations uses hydraulic fracturing or “fracking” technology to increase permeability and enable the gas to be extracted.
Once extracted, the gas is separated from free liquids, such as crude oil, hydrocarbon condensate, water, and entrained solids. The separated gas is further processed to meet specified requirements. For example, natural gas for transmission companies must meet certain pipeline quality specifications with respect to water content, hydrocarbon dew point, heating value, and hydrogen sulfide content.
2] Renewable Natural Gas Production
Chemically identical to conventional natural gas, renewable natural gas (RNG) is the purified product used as a vehicle fuel, which is produced by purifying biogas produced from decaying organic materials. Biomethane, which is another term for this processed pipeline-quality fuel, refers to purified biogas and is interchangeable with traditional natural gas but is often used in non-vehicle applications. Like conventional natural gas, RNG can be compressed (CNG) or liquefied (LNG) for use in vehicles. Learn more about CNG and LNG.
Renewable natural gas (RNG) is a pipeline-quality gas that is fully interchangeable with conventional natural gas and thus can be used in natural gas vehicles. RNG is essentially biogas (the gaseous product of the decomposition of organic matter) that has been processed to purity standards. Like conventional natural gas, RNG can be used as a transportation fuel in the form of compressed natural gas (CNG) or liquefied natural gas (LNG). RNG qualifies as an advanced biofuel under the Renewable Fuel Standard.
Biomethane, which is another term for this purified pipeline-quality fuel, refers to biogas that has also been cleaned and conditioned to remove or reduce non-methane elements. Biogas is produced from various biomass sources through a biochemical process, such as anaerobic digestion, or through thermochemical means, such as gasification. With minor cleanup, biogas can be used to generate electricity and heat and is used as a replacement for traditional natural gas to generate combined electricity and heating for power plants—not in vehicle applications.
To fuel vehicles, biogas must be processed to a higher purity standard. This process is called conditioning or upgrading, and involves the removal of water, carbon dioxide, hydrogen sulfide, and other trace elements. The resulting RNG, or biomethane, has a higher content of methane than raw biogas, which makes it comparable to conventional natural gas and thus a suitable energy source in applications that require pipeline-quality gas, such as vehicle applications.
For a comprehensive list of projects that are upgrading gas for pipeline injection or use as vehicle fuel, see the Renewable Natural Gas Database developed and maintained by Argonne National Laboratory.
Biogas from Landfills
Biogas recovery systems at livestock operations can be used to produce RNG. Animal manure is collected and delivered to an anaerobic digester to stabilize and optimize methane production. The resulting biogas can be processed into RNG and used to fuel natural gas vehicles or produce electricity.
As of 2023, there were about 470 anaerobic digester systems operating at commercial livestock farms in the United States. Most of these facilities use biogas for electricity generation. A few farms are using biogas to produce transportation fuel, including Calgren Dairy Fuels in California and Fair Oaks Farms in Indiana. EPA’s AgSTAR database provides more information about the use of such systems in the United States.
Biogas from Livestock Operations
Biogas recovery systems at livestock operations can be used to produce RNG. Animal manure is collected and delivered to an anaerobic digester to stabilize and optimize methane production. The resulting biogas can be processed into RNG and used to fuel natural gas vehicles or produce electricity.
As of 2023, there were about 470 anaerobic digester systems operating at commercial livestock farms in the United States. Most of these facilities use biogas for electricity generation. A few farms are using biogas to produce transportation fuel, including Calgren Dairy Fuels in California and Fair Oaks Farms in Indiana. EPA’s AgSTAR database provides more information about the use of such systems in the United States.
How Does the United States of America produce Biogas from Wastewater Treatment?
Biogas can be produced by digesting the solids removed in the wastewater treatment process. According to EPA estimates, this biogas potential is about 1 cubic foot of digester gas per 100 gallons of wastewater. Energy generated at U.S. wastewater treatment plants (WWTPs) could potentially meet 12% of the national electricity demand, according to a study released by the National Association of Clean Water Agencies, the Water Environment Research Foundation, and the Water Environment Federation. This could spur some production of RNG for vehicle use as well.
There are more than 16,000 WWTPs in the United States, but only about 1,200 have anaerobic digesters and of those, 860 have the equipment to use their biogas on site. The City of Longmont Wastewater Treatment Plant in Colorado is an example of a plant that uses biogas to produce RNG for use in vehicles.
Other Sources of Biogas
Other sources of biogas include organic waste from industrial, institutional, and commercial entities, such as food manufacturing and wholesalers, supermarkets, restaurants, hospitals, and educational facilities.
Biogas can also be produced from lignocellulosic material (such as crop residues, woody biomass, and dedicated energy crops) via thermochemical conversions, co-digestion, and dry fermentation. These technologies are underway in Europe, with limited applications in the United States.