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Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring
hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prop ...
gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas
mixture consisting of
methane Methane (, ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth ...
and commonly including varying amounts of other higher
alkanes , the simplest alkane In organic chemistry Organic chemistry is a branch of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding.Clayden, J.; Greeves, N. and Warren, S. (20 ...

alkanes
, and sometimes a small percentage of
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
,
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
, or
helium Helium (from el, ἥλιος, helios Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining" ...

helium
. Natural gas is colorless and odorless, and explosive, so a sulfur-smell (similar to rotten eggs) is usually added for early detection of leaks. Natural gas is formed when layers of decomposing plant and animal matter are exposed to intense heat and pressure under the surface of the Earth over millions of years. The energy that the plants originally obtained from the sun is stored in the form of chemical bonds in the gas. Natural gas is a
fossil fuel A fossil fuel is a hydrocarbon In , a hydrocarbon is an consisting entirely of and . Hydrocarbons are examples of s. Hydrocarbons are generally colourless and hydrophobic with only weak odours. Because of their diverse molecular structure ...
. Natural gas is a
non-renewable A non-renewable resource (also called a finite resource) is a natural resource that cannot be readily replaced by natural means at a quick enough pace to keep up with consumption. An example is carbon-based fossil fuel. The original organic matter ...
hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prop ...
used as a source of energy for heating, cooking, and electricity generation. It is also used as a fuel for vehicles and as a chemical feedstock in the manufacture of
plastics Plastics are a wide range of syntheticA synthetic is an artificial material produced by organic chemistry, organic chemical synthesis. Synthetic may also refer to: In the sense of both "combination" and "artificial" * Synthetic chemical or s ...

plastics
and other commercially important
organic chemicals , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other carbon ...
. The extraction and consumption of natural gas is a major and growing driver of
climate change Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...
. It is a potent
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhou ...
itself when released into the atmosphere, and creates
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
when
burnt Burned or burnt may refer to: * Anything which has undergone combustion * Burned (image), quality of an image transformed with loss of detail in all portions lighter than some limit, and/or those darker than some limit * Burnt (film), ''Burnt'' (fi ...
. Natural gas can be efficiently burned to generate heat and
electricity Electricity is the set of physical Physical may refer to: *Physical examination, a regular overall check-up with a doctor *Physical (album), ''Physical'' (album), a 1981 album by Olivia Newton-John **Physical (Olivia Newton-John song), "Physi ...

electricity
, emitting less waste and toxins at the point of use relative to other fossil and
biomass Biomass is plant or animal material used as fuel to produce electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position ...

biomass
fuels. However,
gas venting Gas venting, more specifically known as natural-gas venting or methane venting, is the intentional and controlled release of gases containing alkane hydrocarbons - predominately methane - into earth's atmosphere. It is a widely used method for ...
and flaring, along with unintended
fugitive emissions Fugitive emissions are leaks and other irregular releases of gases or vapors from a pressurized containment - such as appliances, storage tanks, pipelines, wells, or other pieces of equipment - mostly from industrial activities. In addition to t ...
throughout the
supply chain In commerce, a supply chain is a system of organizations, people, activities, information, and resources involved in supplying a product (business), product or service (business), service to a consumer. Supply chain activities involve the transfo ...

supply chain
, can result in a similar
carbon footprint A carbon footprint is the total greenhouse gas (GHG) emissions caused by an individual, event, organization, service, place or product, expressed as carbon dioxide equivalent. Greenhouse gases, including the carbon-containing gases carbon dio ...

carbon footprint
overall. Natural gas is found in deep underground rock formations or associated with other hydrocarbon reservoirs in
coal bed Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements; chiefly hydrogen, sulfur, oxygen, and nitrogen. ...
s and as
methane clathrate . Methane clathrate (CH4·5.75H2O) or (4CH4·23H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large am ...

methane clathrate
s.
Petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

Petroleum
is another fossil fuel found close to and with natural gas. Most natural gas was created over time by two mechanisms: biogenic and thermogenic. Biogenic gas is created by
methanogenic Methanogenesis or biomethanation is the formation of methane Methane ( or ) is a chemical compound with the chemical formula (one atom of carbon and four atoms of hydrogen). It is a group-14 hydride and the simplest alkane , the simplest ...
organisms in
marshes A marsh is a wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes prevailin ...
,
bogs A bog or bogland is a wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes ...
,
landfills A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste w ...
, and shallow sediments. Deeper in the earth, at greater temperature and pressure, thermogenic gas is created from buried organic material. In petroleum production, gas is sometimes burned as flare gas. Before natural gas can be used as a fuel, most, but not all, must be processed to remove impurities, including water, to meet the specifications of marketable natural gas. The by-products of this processing include
ethane Ethane ( or ) is an Organic compound, organic chemical compound with chemical formula . At Standard conditions for temperature and pressure, standard temperature and pressure, ethane is a colorless, odourless gas. Like many hydrocarbons, ethane ...
,
propane Propane () is a three-carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—making four electrons available to form covalen ...

propane
,
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefy, liquefied gas that quickly vaporizes at room temperature. The n ...

butane
s,
pentane Pentane is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ion ...

pentane
s, and higher molecular weight hydrocarbons, hydrogen sulfide (which may be converted into pure
sulfur Sulfur (in nontechnical British English: sulphur) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: th ...

sulfur
),
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
,
water vapor (99.9839 °C) , - , Boiling point The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating th ...
, and sometimes
helium Helium (from el, ἥλιος, helios Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining" ...

helium
and
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
. Natural gas is sometimes informally referred to simply as "gas", especially when it is being compared to other energy sources, such as oil or coal. However, it is not to be confused with
gasoline Gasoline () or petrol () (see the #Etymology, etymology for naming differences and the use of the term ''gas'') is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignition engine, spark-ignite ...

gasoline
, which is often shortened in colloquial usage to "gas", especially in North America.


History

Natural gas was discovered accidentally in ancient China, as it resulted from the drilling for brines. Natural gas was first used by the Chinese in about 500 BC (possibly even 1000 BC). They discovered a way to transport gas seeping from the ground in crude pipelines of bamboo to where it was used to boil salt water to extract the salt in the Ziliujing District of
Sichuan Sichuan (; , ; alternatively romanized as Szechuan or Szechwan) is a landlocked province A province is almost always an administrative division Administrative division, administrative unitArticle 3(1). , country subdivision, admini ...

Sichuan
. The discovery and identification of natural gas in the Americas happened in 1626. In 1821, William Hart successfully dug the first natural gas well at
Fredonia, New York Fredonia is a village in Chautauqua County, New York, United States. The population was 11,230 as of the 2010 census. Fredonia is in the town of Pomfret south of Lake Erie. The village is the home of the State University of New York at Fredoni ...
, United States, which led to the formation of the Fredonia Gas Light Company. The city of
Philadelphia Philadelphia (colloquially known simply as Philly) is the largest city in the Commonwealth A commonwealth is a traditional English term for a political community founded for the common good In philosophy Philosophy (from , ) is ...

Philadelphia
created the first municipally owned natural gas distribution venture in 1836. By 2009, 66 000 km3 (16,000 cu. mi.) (or 8%) had been used out of the total 850 000 km3 (200,000 cu. mi.) of estimated remaining recoverable reserves of natural gas. Based on an estimated 2015 world consumption rate of about 3400 km3 (815 cu. mi.) of gas per year, the total estimated remaining economically recoverable reserves of natural gas would last 250 years at current consumption rates. An annual increase in usage of 2–3% could result in currently recoverable reserves lasting significantly less, perhaps as few as 80 to 100 years.


Sources


Natural gas

In the 19th century, natural gas was primarily obtained as a by-product of . The small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction from the
reservoir A reservoir (; from French ''réservoir'' ) is most commonly an enlarged natural or artificial lake A lake is an area filled with water, localized in a basin, surrounded by land Land is the solid surface of Earth that is not per ...
to the surface, similar to uncapping a soft drink bottle where the carbon dioxide
effervesce Bubbles of carbon dioxide float to the surface of a Soft drink#Carbonated drinks, carbonated soft drink. Effervescence is the escape of gas from an aqueous solution and the foaming or fizzing that results from that release. The word effervescence ...
s. The gas was often viewed as a by-product, a hazard, and a disposal problem in active oil fields. The large volumes produced could not be utilized until relatively expensive
pipeline Pipeline may refer to: Electronics, computers and computing * Pipeline (computing), a chain of data-processing stages or a CPU optimization found on ** Instruction pipelining, a technique for implementing instruction-level parallelism within a si ...
and storage facilities were constructed to deliver the gas to consumer markets. Until the early part of the 20th century, most natural gas associated with oil was either simply released or burned off at oil fields.
Gas venting Gas venting, more specifically known as natural-gas venting or methane venting, is the intentional and controlled release of gases containing alkane hydrocarbons - predominately methane - into earth's atmosphere. It is a widely used method for ...
and production flaring are still practised in modern times, but efforts are ongoing around the world to retire them, and to replace them with other commercially viable and useful alternatives. Unwanted gas (or stranded gas without a market) is often returned to the reservoir with 'injection' wells while awaiting a possible future market or to re-pressurize the formation, which can enhance oil extraction rates from other wells. In regions with a high natural gas demand (such as the US), pipelines are constructed when it is economically feasible to transport gas from a wellsite to an
end consumer A consumer is a person or a group who intends to order, orders, or uses purchased goods, products, or services Service may refer to: Activities :''(See the Religion section for religious activities)'' * Administrative service, a required part o ...
. In addition to transporting gas via pipelines for use in power generation, other end uses for natural gas include export as
liquefied natural gas Liquefied natural gas (LNG) is natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting of methane and commonly including varying amounts of other higher alkanes, and s ...

liquefied natural gas
(LNG) or conversion of natural gas into other liquid products via
gas to liquidsGas to liquids (GTL) is a refinery process to convert natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts ...
(GTL) technologies. GTL technologies can convert natural gas into liquids products such as gasoline, diesel or jet fuel. A variety of GTL technologies have been developed, including Fischer–Tropsch (F–T), methanol to gasoline (MTG) and syngas to gasoline plus (STG+). F–T produces a synthetic crude that can be further refined into finished products, while MTG can produce synthetic gasoline from natural gas. STG+ can produce drop-in gasoline, diesel, jet fuel and aromatic chemicals directly from natural gas via a single-loop process. In 2011, Royal Dutch Shell's per day F–T plant went into operation in
Qatar Qatar (, , or ; ar, قطر, Qaṭar ; local vernacular pronunciation: ), officially the State of Qatar,) is a country in Western Asia. It occupies the small Qatar Peninsula on the northeastern coast of the Arabian Peninsula, and shares it ...

Qatar
. Natural gas can be "associated" (found in
oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons In organic chemistry, a hydrocarbon is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally ...

oil field
s), or "non-associated" (isolated in
natural gas field A petroleum reservoir or oil and gas reservoir is a subsurface pool of hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any che ...
s), and is also found in
coal bed Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements; chiefly hydrogen, sulfur, oxygen, and nitrogen. ...
s (as
coalbed methane Coalbed methane (CBM or coal-bed methane), coalbed gas, coal seam gas (CSG), or coal-mine methane (CMM) is a form of natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consi ...
). It sometimes contains a significant amount of
ethane Ethane ( or ) is an Organic compound, organic chemical compound with chemical formula . At Standard conditions for temperature and pressure, standard temperature and pressure, ethane is a colorless, odourless gas. Like many hydrocarbons, ethane ...
,
propane Propane () is a three-carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—making four electrons available to form covalen ...

propane
,
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefy, liquefied gas that quickly vaporizes at room temperature. The n ...

butane
, and
pentane Pentane is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ion ...

pentane
—heavier hydrocarbons removed for commercial use prior to the
methane Methane (, ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth ...
being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
,
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
helium Helium (from el, ἥλιος, helios Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining" ...

helium
(rarely), and
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
must also be removed before the natural gas can be transported. Natural gas extracted from oil wells is called casinghead gas (whether or not truly produced up the annulus and through a casinghead outlet) or associated gas. The natural gas industry is extracting an increasing quantity of gas from challenging resource types:
sour gas Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S). Natural gas is usually considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas, which is equivalent to approximat ...
,
tight gas Tight gas is natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes ...
,
shale gas 400px, Total natural gas rig count in the US (including conventional gas drilling) Shale gas is natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of ...
, and
coalbed methane Coalbed methane (CBM or coal-bed methane), coalbed gas, coal seam gas (CSG), or coal-mine methane (CMM) is a form of natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consi ...
. There is some disagreement on which country has the largest proven gas reserves. Sources that consider that Russia has by far the largest proven reserves include the US CIA (47 600 km3), the US Energy Information Administration (47 800 km3), and OPEC (48 700 km3). However, BP credits Russia with only 32 900 km3, which would place it in second place, slightly behind Iran (33 100 to 33 800 km3, depending on the source). With
Gazprom PJSC Gazprom (russian: Газпром, ) is a Russian majority state-owned multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body f ...
, Russia is frequently the world's largest natural gas extractor. Major proven resources (in cubic kilometers) are world 187 300 (2013), Iran 33 600 (2013), Russia 32 900 (2013), Qatar 25 100 (2013), Turkmenistan 17 500 (2013) and the United States 8500 (2013). It is estimated that there are about 900 000 km3 of "unconventional" gas such as shale gas, of which 180 000 km3 may be recoverable. In turn, many studies from
MIT Massachusetts Institute of Technology (MIT) is a private land-grant research university A research university is a university A university ( la, universitas, 'a whole') is an educational institution, institution of higher education, hi ...

MIT
,
Black & Veatch Black & Veatch is the largest engineering firm in the Kansas City metropolitan area. Founded in 1915 in Kansas City, Missouri it is now headquartered in Overland Park, Kansas It is a global engineering, procurement, construction (Engineering, procu ...
and the DOE predict that natural gas will account for a larger portion of electricity generation and heat in the future. The world's largest gas field is the offshore
South Pars / North Dome Gas-Condensate field The South Pars/North Dome field is a natural-gas condensate field located in the Persian Gulf. It is by far the world's largest natural gas field,International Energy Agency, IEA, World Energy Outlook 2008 - Chapter 12 - Natural gas resources and pr ...
, shared between Iran and Qatar. It is estimated to have of natural gas and of natural gas condensates. Because natural gas is not a pure product, as the reservoir pressure drops when non-associated gas is extracted from a field under supercritical (pressure/temperature) conditions, the higher molecular weight components may partially condense upon isothermic depressurizing—an effect called retrograde condensation. The liquid thus formed may get trapped as the pores of the gas reservoir get depleted. One method to deal with this problem is to re-inject dried gas free of condensate to maintain the underground pressure and to allow re-evaporation and extraction of condensates. More frequently, the liquid condenses at the surface, and one of the tasks of the gas plant is to collect this condensate. The resulting liquid is called natural gas liquid (NGL) and has commercial value.


Shale gas

Shale gas is natural gas produced from
shale Shale is a fine-grained, clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defi ...

shale
. Because shale has matrix permeability too low to allow gas to flow in economical quantities, shale gas wells depend on fractures to allow the gas to flow. Early shale gas wells depended on natural fractures through which gas flowed; almost all shale gas wells today require fractures artificially created by
hydraulic fracturing Hydraulic fracturing, also called fracking, hydrofracking, and hydrofracturing, is a well stimulation technique involving the fracturing of bedrock Formation (geology), formations by a pressurized liquid. The process involves the high-pressur ...
. Since 2000, shale gas has become a major source of natural gas in the United States and Canada. Because of increased shale gas production the United States was in 2014 the number one natural gas producer in the world. The production of shale gas in the United States has been described as a "shale gas revolution" and as "one of the landmark events in the 21st century." Following the increased production in the United States, shale gas exploration is beginning in countries such as Poland, China, and South Africa. Chinese geologists have identified the
Sichuan Basin The Sichuan Basin (), formerly transliterated as the Szechwan Basin, sometimes called the Red Basin, is a Sedimentary basin, lowland region in southwestern China. It is surrounded by mountains on all sides and is drained by the upper Yangtze River ...
as a promising target for shale gas drilling, because of the similarity of shales to those that have proven productive in the United States. Production from the Wei Wei 201 well is 1×104–2×104 m3 per day. In late 2020, China National Petroleum Corporation claimed daily production of 20 million cubic meters of gas from its Changning-Weiyuan demonstration zone.


Town gas

Town gas Coal gas is a flammable gaseous fuel made from coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, ...
is a flammable gaseous fuel made by the destructive distillation of
coal Coal is a combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , ...

coal
. It contains a variety of calorific gases including
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
,
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom. It is the simplest molecule of the oxocarbon family. In ...

carbon monoxide
,
methane Methane (, ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth ...
, and other volatile
hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prop ...
s, together with small quantities of non-calorific gases such as
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
and
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
, and is used in a similar way to natural gas. This is a historical technology and is not usually economically competitive with other sources of fuel gas today. Most town "gashouses" located in the eastern US in the late 19th and early 20th centuries were simple by-product coke ovens that heated bituminous coal in air-tight chambers. The gas driven off from the coal was collected and distributed through networks of pipes to residences and other buildings where it was used for cooking and lighting. (Gas heating did not come into widespread use until the last half of the 20th century.) The
coal tar Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas Coal gas is a flammable gaseous fuel Fuel gas is any one of a number of fuels that under ordinary conditions are gaseous. Many fuel gases are c ...
(or
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous The viscosity of a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or externa ...

asphalt
) that collected in the bottoms of the gashouse ovens was often used for roofing and other waterproofing purposes, and when mixed with sand and gravel was used for paving streets.


Crystallized natural gas – hydrates

Huge quantities of natural gas (primarily methane) exist in the form of under sediment on offshore continental shelves and on land in arctic regions that experience
permafrost Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean The ocean (also the or the world ocean) is the body of that covers approximately 70.8% of the surfa ...

permafrost
, such as those in
Siberia Siberia (; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of R ...

Siberia
. Hydrates require a combination of high pressure and low temperature to form. In 2010, the cost of extracting natural gas from crystallized natural gas was estimated to be as much as twice the cost of extracting natural gas from conventional sources, and even higher from offshore deposits. In 2013, Japan Oil, Gas and Metals National Corporation (JOGMEC) announced that they had recovered commercially relevant quantities of natural gas from methane hydrate.


Processing

The image below is a schematic block flow diagram of a typical natural gas processing plant. It shows the various unit processes used to convert raw natural gas into sales gas pipelined to the end user markets. The block flow diagram also shows how processing of the raw natural gas yields byproduct sulfur, byproduct ethane, and natural gas liquids (NGL) propane, butanes and natural gasoline (denoted as pentanes +).


Depletion

As of mid-2020, natural gas production in the US has peaked three times, with current levels exceeding both previous peaks. It reached 24.1 trillion cubic feet per year in 1973, followed by a decline, and reached 24.5 trillion cubic feet in 2001. After a brief drop, withdrawals increased nearly every year since 2006 (owing to the shale gas boom), with 2017 production at 33.4 trillion cubic feet and 2019 production at 40.7 trillion cubic feet. After the third peak in December 2019, extraction continued to fall from March onward due to decreased demand caused by the COVID-19 pandemic in the US. The 2021 global energy crisis was driven by a global surge in demand as the world quit the economic recession caused by COVID-19, particularly due to strong energy demand in Asia.


Storage and transport

Because of its low density, it is not easy to store natural gas or to transport it by vehicle. Natural gas pipelines are impractical across oceans, since the gas needs to be cooled down and compressed, as the friction in the pipeline causes the gas to heat up. Many are close to reaching their capacity, prompting some politicians representing northern states to speak of potential shortages. The large trade cost implies that natural gas markets are globally much less integrated, causing significant price differences across countries. In
Western Europe Western Europe is the western region of Europe Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical r ...

Western Europe
, the gas pipeline network is already dense. New pipelines are planned or under construction in
Eastern Europe Eastern Europe is the eastern region of Europe Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical reg ...

Eastern Europe
and between gas fields in
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

Russia
,
Near East The Near East ( ar, الشرق الأدنى, al-Sharq al-'Adnā, he, המזרח הקרוב, arc, ܕܢܚܐ ܩܪܒ, fa, خاور نزدیک, Xāvar-e nazdik, tr, Yakın Doğu) is a geographical term which roughly encompasses a transcontinental ...
and
Northern Africa North Africa or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in th ...

Northern Africa
and Western Europe. Whenever gas is bought or sold at custody transfer points, rules and agreements are made regarding the gas quality. These may include the maximum allowable concentration of

,

and . Usually sales quality gas that has been treated to remove contamination is traded on a "dry gas" basis and is required to be commercially free from objectionable odours, materials, and dust or other solid or liquid matter, waxes, gums and gum forming constituents, which might damage or adversely affect operation of equipment downstream of the custody transfer point.
LNG carrier An LNG carrier is a tank ship designed for transporting liquefied natural gas (LNG). As the LNG market grows rapidly, the fleet of LNG carriers continues to experience tremendous growth. History The first LNG carrier ''Methane Pioneer'' (), cl ...
s transport liquefied natural gas (LNG) across oceans, while
tank truck A tank truck, gas truck, fuel truck, or tanker truck (United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located ...
s can carry liquefied or compressed natural gas (CNG) over shorter distances. Sea transport using CNG carrier ships that are now under development may be competitive with LNG transport in specific conditions. Gas is turned into liquid at a
liquefaction In materials science The interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of two or more academic discipline An academic discipline or academic field is a subdivision of knowledge that is Educ ...
plant, and is returned to gas form at
regasification 220px, Regasification terminal of Tokyo Gas in Yokohama Regasification is a process of converting liquefied natural gas (LNG) at −162 °C (−260 °F) temperature back to natural gas at atmospheric temperature. LNG gasification plants can be loc ...

regasification
plant at the terminal. Shipborne regasification equipment is also used. LNG is the preferred form for long distance, high volume transportation of natural gas, whereas pipeline is preferred for transport for distances up to over land and approximately half that distance offshore. CNG is transported at high pressure, typically above . Compressors and decompression equipment are less capital intensive and may be economical in smaller unit sizes than liquefaction/regasification plants. Natural gas trucks and carriers may transport natural gas directly to end-users, or to distribution points such as pipelines. In the past, the natural gas which was recovered in the course of recovering
petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

petroleum
could not be profitably sold, and was simply burned at the oil field in a process known as flaring. Flaring is now illegal in many countries. Additionally, higher demand in the last 20–30 years has made production of gas associated with oil economically viable. As a further option, the gas is now sometimes re- injected into the formation for enhanced oil recovery by pressure maintenance as well as miscible or immiscible flooding. Conservation, re-injection, or flaring of natural gas associated with oil is primarily dependent on proximity to markets (pipelines), and regulatory restrictions. Natural gas can be indirectly exported through the absorption in other physical output. A recent study suggests that the expansion of shale gas production in the US has caused prices to drop relative to other countries. This has caused a boom in energy intensive manufacturing sector exports, whereby the average dollar unit of US manufacturing exports has almost tripled its energy content between 1996 and 2012. A "master gas system" was invented in Saudi Arabia in the late 1970s, ending any necessity for flaring. Satellite and nearby infra-red camera observations, however, shows that flaring and venting are still happening in some countries. Natural gas is used to generate electricity and heat for desalination. Similarly, some landfills that also discharge methane gases have been set up to capture the methane and generate electricity. Natural gas is often stored underground inside depleted gas reservoirs from previous gas wells, salt domes, or in tanks as liquefied natural gas. The gas is injected in a time of low demand and extracted when demand picks up. Storage nearby end users helps to meet volatile demands, but such storage may not always be practicable. With 15 countries accounting for 84% of the worldwide extraction, access to natural gas has become an important issue in international politics, and countries vie for control of pipelines. In the first decade of the 21st century,
Gazprom PJSC Gazprom (russian: Газпром, ) is a Russian majority state-owned multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body f ...
, the state-owned energy company in Russia, engaged in disputes with Ukraine and Belarus over the price of natural gas, which have created concerns that gas deliveries to parts of Europe could be cut off for political reasons. The United States is preparing to export natural gas.


Floating liquefied natural gas

Floating liquefied natural gas (FLNG) is an innovative technology designed to enable the development of offshore gas resources that would otherwise remain untapped due to environmental or economic factors which currently make them impractical to develop via a land-based LNG operation. FLNG technology also provides a number of environmental and economic advantages: * Environmental – Because all processing is done at the gas field, there is no requirement for long pipelines to shore, compression units to pump the gas to shore, dredging and jetty construction, and onshore construction of an LNG processing plant, which significantly reduces the environmental footprint. Avoiding construction also helps preserve marine and coastal environments. In addition, environmental disturbance will be minimised during decommissioning because the facility can easily be disconnected and removed before being refurbished and re-deployed elsewhere. * Economic – Where pumping gas to shore can be prohibitively expensive, FLNG makes development economically viable. As a result, it will open up new business opportunities for countries to develop offshore gas fields that would otherwise remain stranded, such as those offshore East Africa. Many gas and oil companies are considering the economic and environmental benefits of floating liquefied natural gas (FLNG). There are currently projects underway to construct five FLNG facilities. Petronas is close to completion on their FLNG-1 at Daewoo Shipbuilding and Marine Engineering and are underway on their FLNG-2 project at Samsung Heavy Industries. Shell Prelude is due to start production 2017. The Browse LNG project will commence Front-end loading, FEED in 2019.


Uses

Natural gas is primarily used in the northern hemisphere. North America and Europe are major consumers.


Mid-stream natural gas

Often well head gases require removal of various hydrocarbon molecules contained within the gas. Some of these gases include heptane,
pentane Pentane is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ion ...

pentane
,
propane Propane () is a three-carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—making four electrons available to form covalen ...

propane
and other hydrocarbons with molecular weights above
methane Methane (, ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth ...
(). The natural gas transmission lines extend to the natural gas processing plant or unit which removes the higher molecular weighted hydrocarbons to produce natural gas with energy content between . The processed natural gas may then be used for residential, commercial and industrial uses. Natural gas flowing in the distribution lines is called mid-stream natural gas and is often used to power engines which rotate compressors. These compressors are required in the transmission line to pressurize and repressurize the mid-stream natural gas as the gas travels. Typically, natural gas powered engines require natural gas to operate at the rotational name plate specifications. Several methods are used to remove these higher molecular weighted gases for use by the natural gas engine. A few technologies are as follows: * Joule–Thomson effect, Joule–Thomson skid * Cryogenic or chiller system * Chemical enzymology system


Power generation

Natural gas is a major source of electricity generation through the use of cogeneration, gas turbines and steam turbines. Natural gas is also well suited for a combined use in association with renewable energy sources such as wind or solar energy, solar and for alimenting Load profile, peak-load power stations functioning in tandem with hydroelectric plants. Most grid peaking power plants and some off-grid engine-generators use natural gas. Particularly high efficiencies can be achieved through combining gas turbines with a steam turbine in combined cycle mode. Natural gas burns more cleanly than other fuels, such as oil and coal. Because burning natural gas produces both water and carbon dioxide, it produces less carbon dioxide per unit of energy released than coal, which produces mostly carbon dioxide. Burning natural gas produces only about half the carbon dioxide per kilowatt-hour (kWh) that
coal Coal is a combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , ...

coal
does. For transportation, burning natural gas produces about 30% less carbon dioxide than burning
petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

petroleum
. The US Energy Information Administration reports the emissions in million Tonne, metric tons of carbon dioxide in the world for 2012: * Natural gas: 6,799 * Petroleum: 11,695 * Coal: 13,787 Coal-fired electric power generation emits around of carbon dioxide for every megawatt-hour (MWh) generated, which is almost double the carbon dioxide released by natural gas-fired generation. Because of this higher carbon efficiency of natural gas generation, as the fuel mix in the United States has changed to reduce coal and increase natural gas generation, carbon dioxide emissions have unexpectedly fallen. Those measured in the first quarter of 2012 were the lowest of any recorded for the first quarter of any year since 1992. Combined cycle power generation using natural gas is currently the cleanest available source of power using hydrocarbon fuels, and this technology is widely and increasingly used as natural gas can be obtained at increasingly reasonable costs. Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not Natural gas prices, price-competitive. Locally produced electricity and heat using natural gas powered Combined Heat and Power plant (CHP or Cogeneration plant) is considered energy efficient and a rapid way to cut carbon emissions. Natural gas generated power has increased from 740 TWh in 1973 to 5140 TWh in 2014, generating 22% of the worlds total electricity, approximately half as much as generated with coal. Efforts around the world to reduce the use of coal has led some regions to Fossil fuel phase-out#Switch to natural gas, switch to natural gas.


Domestic use

Natural gas dispensed in a residential setting can generate temperatures in excess of making it a powerful domestic cooking and heating fuel. In much of the developed world it is supplied through pipes to homes, where it is used for many purposes including ranges and ovens, gas-heated clothes dryers, HVAC, heating/air conditioning, cooling, and central heating. Heaters in homes and other buildings may include boilers, Furnace (house heating), furnaces, and water heating, water heaters. Both North America and Europe are major consumers of natural gas. Domestic appliances, furnaces, and boilers use low pressure, usually 6 to 7 inch of water, inches of water (6" to 7" WC), which is about 0.25 psig. The pressures in the supply lines vary, either utilization pressure (UP, the aforementioned 6" to 7" WC) or elevated pressure (EP), which may be anywhere from 1 psig to 120 psig. Systems using EP have a pressure regulator, regulator at the service entrance to step down the pressure to UP. Natural Gas Piping Systems inside buildings are often designed with pressures of 2 to 5 psi (13.8 to 34.5 kPa), and have downstream pressure regulators to reduce pressure as needed. The maximum allowable operating pressure for natural gas piping systems within a building is based on NFPA 54: National Fuel Gas Code, except when approved by the Public Safety Authority or when insurance companies have more stringent requirements. Generally, natural gas system pressures are not allowed to exceed 5 psig (34.5 kPa) unless all of the following conditions are met: * The AHJ will allow a higher pressure. * The distribution pipe is welded. (Note: 2. Some jurisdictions may also require that welded joints be radiographed to verify continuity). * The pipes are closed for protection and placed in a ventilated area that does not allow gas accumulation. * The pipe is installed in the areas used for industrial processes, research, storage or mechanical equipment rooms. Generally, a maximum liquefied petroleum gas pressure of 20 psig (138 kPa) is allowed, provided the building is used specifically for industrial or research purposes and is constructed in accordance with NFPA 58: Liquefied Petroleum Gas Code, Chapter 7. A seismic earthquake valve operating at a pressure of 55 psig (3.7 bar) can stop the flow of natural gas into the site wide natural gas distribution piping network (that runs (outdoors underground, above building roofs, and or within the upper supports of a canopy roof). Seismic earthquake valves are designed for use at a maximum of 60 psig. In Australia, natural gas is transported from gas processing facilities to regulator stations via Transmission pipelines. Gas is then regulated down to distributed pressures and the gas is distributed around a gas network via gas mains. Small branches from the network, called services, connect individual domestic dwellings, or multi-dwelling buildings to the network. The networks typically range in pressures from 7 kPa (low pressure) to 515 kPa (high pressure). Gas is then regulated down to 1.1 kPa or 2.75 kPa, before being metered and passed to the consumer for domestic use. Natural gas mains are made from a variety of materials: historically cast iron, though more modern mains are made from steel or polyethylene. In the US compressed natural gas (CNG) is available in some rural areas as an alternative to less expensive and more abundant LPG (liquefied petroleum gas), the dominant source of rural gas. It is used in homes lacking direct connections to public utility provided gas, or to fuel portable Grill (cooking), grills. Natural gas is also supplied by independent natural gas suppliers through Natural Gas Choice programs throughout the United States.


Transportation

CNG is a cleaner and also cheaper alternative to other automobile fuels such as
gasoline Gasoline () or petrol () (see the #Etymology, etymology for naming differences and the use of the term ''gas'') is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignition engine, spark-ignite ...

gasoline
(petrol). By the end of 2014, there were over 20 million natural gas vehicles worldwide, led by Iran (3.5 million), China (3.3 million), Pakistan (2.8 million), Argentina (2.5 million), India (1.8 million), and Brazil (1.8 million). The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines. Gasoline/petrol vehicles converted to run on natural gas suffer because of the low compression ratio of their engines, resulting in a cropping of delivered power while running on natural gas (10–15%). CNG-specific engines, however, use a higher compression ratio due to this fuel's higher octane number of 120–130. Besides use in road vehicles, CNG can also be used in aircraft. Compressed natural gas has been used in some aircraft like the Aviat Aircraft Husky 200 CNG and the Chromarat VX-1 KittyHawk LNG is also being used in aircraft.
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

Russia
n aircraft manufacturer Tupolev for instance is running a development program to produce LNG- and
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
-powered aircraft. The program has been running since the mid-1970s, and seeks to develop LNG and hydrogen variants of the Tupolev Tu-204, Tu-204 and Tupolev Tu-334, Tu-334 passenger aircraft, and also the Tupolev Tu-330, Tu-330 cargo aircraft. Depending on the current market price for jet fuel and LNG, fuel for an LNG-powered aircraft could cost 5,000 Russian ruble, rubles (US$100) less per tonne, roughly 60%, with considerable reductions to
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom. It is the simplest molecule of the oxocarbon family. In ...

carbon monoxide
,
hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prop ...
and nitrogen oxide emissions. The advantages of liquid methane as a jet engine fuel are that it has more specific energy than the standard kerosene mixes do and that its low temperature can help cool the air which the engine compresses for greater volumetric efficiency, in effect replacing an intercooler. Alternatively, it can be used to lower the temperature of the exhaust.


Fertilizers

Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production.


Hydrogen

Natural gas can be used to produce
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
, with one common method being the hydrogen reformer. Hydrogen has many applications: it is a primary feedstock for the chemical industry, a hydrogenating agent, an important commodity for oil refineries, and the fuel source in hydrogen vehicles.


Animal and fish feed

Protein rich animal and fish feed is produced by feeding natural gas to Methylococcus capsulatus bacteria on commercial scale.


Other

Natural gas is also used in the manufacture of textile, fabrics, glass, steel, plastics, paint, synthetic oil, and other products. The first step in the valorization of natural gas components is usually the of the alkane into olefin. The oxidative dehydrogenation of ethane leads to ethylene which can be converted forther to ethylene epoxide, ethylene glycol, acetaldehyde or other olefins. Propane can be converted to propylene or can be oxidized to acrylic acid and acrylonitrile.


Environmental effects


Greenhouse gas effect of natural gas release

Human activity is responsible for about 60% of all methane emissions and for most of the resulting increase in atmospheric methane.Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang (2013
"Anthropogenic and Natural Radiative Forcing"
Table 8.7 on page 714. In: ''Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change''. Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
Anthropogenic and Natural Radiative Forcing
/ref> Natural gas is intentionally released or is otherwise known to leak during the extraction, storage, transportation, and distribution of fossil fuels. Globally, this accounts for an estimated 33% of anthropogenic
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhou ...
warming. The decomposition of municipal solid waste (a source of landfill gas) and wastewater account for an additional 18% of such emissions. These estimates include substantial uncertainties which should be reduced in the near future with improved Earth observation satellite, satellite measurements, such as those planned fo
MethaneSAT
After release to the atmosphere, methane is removed by gradual oxidation to carbon dioxide and water by hydroxyl radicals () formed in the troposphere or stratosphere, giving the overall chemical reaction + 2 → + 2. While the lifetime of atmospheric methane is relatively short when compared to carbon dioxide, with a half-life of about 7 years, it is more efficient at trapping heat in the atmosphere, so that a given quantity of methane has 84 times the global-warming potential of carbon dioxide over a 20-year period and 28 times over a 100-year period. Natural gas is thus a potent greenhouse gas due to the strong radiative forcing of methane in the short term, and the continuing effects of carbon dioxide in the longer term. Targeted efforts to reduce warming quickly by reducing anthropogenic methane emissions is a climate change mitigation strategy supported by the Global Methane Initiative.


Greenhouse gas emissions

When refined and burned, natural gas can produce 25–30% less carbon dioxide per joule delivered than oil, and 40–45% less than coal. It can also produce potentially fewer toxic pollutants than other hydrocarbon fuels. However, compared to other major fossil fuels, natural gas causes more emissions in relative terms during the production and transportation of the fuel, meaning that the life cycle greenhouse gas emissions are about 47 % higher than the direct emissions from the site of consumption. In terms of the warming effect over 100 years, natural gas production and use comprises about one fifth of human greenhouse gas emissions, and this contribution is growing rapidly. Globally, natural gas use emitted about 7.8 billion tons of in 2018 (including flaring), while coal and oil use emitted 14.7 and 12.4 billion tons, respectively. In 2019 45 megatonnes of methane was released. According to an updated version of the Special Report on Emissions Scenarios#B2, Special Report on Emissions Scenario, by 2030 natural gas would be the source of 11 billion tons a year because demand is increasing 1.9% per year. The continued financing and construction of new gas pipelines indicates that huge emissions of fossil greenhouse gases could be locked-in for 40 to 50 years into the future. In the U.S. state of Texas alone, five new long-distance gas pipelines have been under construction, with the first entering service in 2019, and the others scheduled to come online during 2020–2022. To reduce its greenhouse emissions, the Netherlands is subsidizing a transition away from natural gas for all homes in the country by 2050. In Amsterdam, no new residential gas accounts have been allowed since 2018, and all homes in the city are expected to be converted by 2040 to use the excess heat from adjacent industrial buildings and operations. Some cities in the United States have started prohibiting gas hookups for new houses, with state laws passed and under consideration to either require electrification or prohibit local requirements. The UK government is also experimenting with alternative home heating technologies to meet its climate goals. To preserve their businesses, natural gas utilities in the United States have been lobbying for laws preventing local electrification ordinances, and are promoting renewable natural gas and hydrogen fuel.


Other pollutants

Natural gas produces far lower amounts of sulfur dioxide and NOx, nitrogen oxides than other fossil fuels. The pollutants due to natural gas combustion are listed below:


Radionuclides

Natural gas extraction also produces radioactive isotopes of polonium (Po-210), lead (Pb-210) and radon (Rn-220). Radon is a gas with initial activity from 5 to 200,000 becquerels per cubic meter of gas. It decays rapidly to Pb-210 which can build up as a thin film in gas extraction equipment.


Safety concerns

The natural gas extraction workforce face unique health and safety challenges and is recognized by the National Institute for Occupational Safety and Health (NIOSH) as a priority industry sector in the National Occupational Research Agenda (NORA) to identify and provide intervention strategies regarding occupational health and safety issues.


Production

Some gas fields yield
sour gas Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S). Natural gas is usually considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas, which is equivalent to approximat ...
containing
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
(), a toxic compound when inhaled. Amine gas treating, an industrial scale process which removes acidic
gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas
eous components, is often used to remove hydrogen sulfide from natural gas. Extraction of natural gas (or oil) leads to decrease in pressure in the oil reservoir, reservoir. Such decrease in pressure in turn may result in subsidence, sinking of the ground above. Subsidence may affect ecosystems, waterways, sewer and water supply systems, foundations, and so on.


Fracking

Releasing natural gas from subsurface porous rock formations may be accomplished by a process called
hydraulic fracturing Hydraulic fracturing, also called fracking, hydrofracking, and hydrofracturing, is a well stimulation technique involving the fracturing of bedrock Formation (geology), formations by a pressurized liquid. The process involves the high-pressur ...
or "fracking". It is estimated that hydraulic fracturing will eventually account for nearly 70% of natural gas development in North America. Since the first commercial hydraulic fracturing operation in 1949, approximately one million wells have been hydraulically fractured in the United States. The production of natural gas from hydraulically fractured wells has utilized the technological developments of directional and horizontal drilling, which improved access to natural gas in tight rock formations. Strong growth in the production of unconventional gas from hydraulically fractured wells occurred between 2000 and 2012. In hydraulic fracturing, well operators force water mixed with a variety of chemicals through the wellbore casing into the rock. The high pressure water breaks up or "fracks" the rock, which releases gas from the rock formation. Sand and other particles are added to the water as a proppant to keep the fractures in the rock open, thus enabling the gas to flow into the casing and then to the surface. Chemicals are added to the fluid to perform such functions as reducing friction and inhibiting corrosion. After the "frack," oil or gas is extracted and 30–70% of the frack fluid, i.e. the mixture of water, chemicals, sand, etc., flows back to the surface. Many gas-bearing formations also contain water, which will flow up the wellbore to the surface along with the gas, in both hydraulically fractured and non-hydraulically fractured wells. This produced water often has a high content of salt and other dissolved minerals that occur in the formation. The volume of water used to hydraulically fracture wells varies according to the hydraulic fracturing technique. In the United States, the average volume of water used per hydraulic fracture has been reported as nearly 7,375 gallons for vertical oil and gas wells prior to 1953, nearly 197,000 gallons for vertical oil and gas wells between 2000 and 2010, and nearly 3 million gallons for horizontal gas wells between 2000 and 2010. Determining which fracking technique is appropriate for well productivity depends largely on the properties of the reservoir rock from which to extract oil or gas. If the rock is characterized by low-permeability – which refers to its ability to let substances, i.e. gas, pass through it, then the rock may be considered a source of
tight gas Tight gas is natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes ...
. Fracking for shale gas, which is currently also known as a source of unconventional gas, involves drilling a borehole vertically until it reaches a lateral shale rock formation, at which point the drill turns to follow the rock for hundreds or thousands of feet horizontally. In contrast, conventional oil and gas sources are characterized by higher rock permeability, which naturally enables the flow of oil or gas into the wellbore with less intensive hydraulic fracturing techniques than the production of tight gas has required. The decades in development of drilling technology for conventional and unconventional oil and gas production have not only improved access to natural gas in low-permeability reservoir rocks, but also posed significant adverse impacts on environmental and public health. The US EPA has acknowledged that toxic, carcinogenic chemicals, i.e. benzene and ethylbenzene, have been used as gelling agents in water and chemical mixtures for high volume horizontal fracturing (HVHF). Following the hydraulic fracture in HVHF, the water, chemicals, and frack fluid that return to the well's surface, called flowback or produced water, may contain radioactive materials, heavy metals, natural salts, and hydrocarbons which exist naturally in shale rock formations. Fracking chemicals, radioactive materials, heavy metals, and salts that are removed from the HVHF well by well operators are so difficult to remove from the water they're mixed with, and would so heavily water pollution, pollute the water cycle, that most of the flowback is either recycled into other fracking operations or injected into deep underground wells, eliminating the water that HVHF required from the hydrologic cycle. Historically low gas prices have delayed the nuclear renaissance, as well as the development of solar thermal energy.


Added odor

Natural gas in its native state is colorless and almost odor, odorless. In order to assist consumers in detecting leaks, an odorizer with a scent similar to rotten eggs, tert-Butylthiol (t-butyl mercaptan), is added. Sometimes a related compound, tetrahydrothiophene, thiophane, may be used in the mixture. Situations in which an odorant that is added to natural gas can be detected by analytical instrumentation, but cannot be properly detected by an observer with a normal sense of smell, have occurred in the natural gas industry. This is caused by odor masking, when one odorant overpowers the sensation of another. As of 2011, the industry is conducting research on the causes of odor masking.


Risk of explosion

List of pipeline accidents, Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and other structures are most frequently affected when an internal leak builds up gas inside the structure. Frequently, the blast is powerful enough to significantly damage a building but leave it standing. In these cases, the people inside tend to have minor to moderate injuries. Occasionally, the gas can collect in high enough quantities to cause a deadly explosion, destroying one or more buildings in the process. Many building codes now forbid the installation of gas pipes inside cavity walls or below floor boards to mitigate against this risk. Gas usually dissipates readily outdoors, but can sometimes collect in dangerous quantities if flow rates are high enough. From 1994 through 2013, the United States had 745 serious incidents with gas distribution, causing 278 fatalities and 1,059 injuries, with $110,658,083 in property damage. However, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is low.


Risk of carbon monoxide inhalation

Natural gas heating systems may cause carbon monoxide poisoning if unvented or poorly vented. In 2011, natural gas furnaces, space heaters, water heaters and stoves were blamed for 11 carbon monoxide deaths in the US. Another 22 deaths were attributed to appliances running on liquified petroleum gas, and 17 deaths on gas of unspecified type. Improvements in natural gas furnace designs have greatly reduced CO poisoning concerns. Carbon monoxide detector, Detectors are also available that warn of carbon monoxide or explosive gases such as methane and propane.


Energy content, statistics, and pricing

Quantities of natural gas are measured in normal cubic meters (cubic meter of gas at "normal" temperature and pressure ) or Standard cubic foot, standard cubic feet (cubic foot of gas at "standard" temperature and pressure ), . The higher heating value, gross heat of combustion of commercial quality natural gas is around , but this can vary by several percent. This is about (assuming a density of , an approximate value). Except in the European Union, the U.S., and Canada, natural gas is sold in gigajoule retail units. LNG (liquefied natural gas) and LPG (liquefied petroleum gas) are traded in metric tonnes (1,000 kg) or million BTU as spot deliveries. Long term natural gas distribution contracts are signed in cubic meters, and LNG contracts are in metric tonnes. The LNG and LPG is transported by specialized LNG carrier, transport ships, as the gas is liquified at cryogenic temperatures. The specification of each LNG/LPG cargo will usually contain the energy content, but this information is in general not available to the public. In the Russian Federation,
Gazprom PJSC Gazprom (russian: Газпром, ) is a Russian majority state-owned multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body f ...
sold approximately of natural gas in 2008. In 2013 they produced of natural and associated gas. Gazprom supplied Europe with of gas in 2013. In August 2015, possibly the largest natural gas discovery in history was made and notified by an Italian gas company ENI. The energy company indicated that it has unearthed a Giant oil and gas fields, "supergiant" gas field in the Mediterranean Sea covering about . This was named the Zohr Field, Zohr gas field and could hold a potential of natural gas. ENI said that the energy is about . The Zohr Field, Zohr field was found in the deep waters off the northern coast of Egypt and ENI claims that it will be the largest ever in the Mediterranean and even the world.


European Union

Gas prices for end users vary greatly across the European Union, EU. A single European energy market, one of the key objectives of the EU, should level the prices of gas in all EU member states. Moreover, it would help to resolve supply and global warming issues, as well as strengthen relations with other Mediterranean countries and foster investments in the region.


United States

In United States customary units, US units, of natural gas produces around . The actual heating value when the water formed does not condense is the lower heating value, net heat of combustion and can be as much as 10% less. In the United States, retail sales are often in units of therms (th); 1 therm = 100,000 BTU. Gas sales to domestic consumers are often in units of 100 standard cubic feet (scf). Gas meters measure the volume of gas used, and this is converted to therms by multiplying the volume by the energy content of the gas used during that period, which varies slightly over time. The typical annual consumption of a single family residence is 1,000 therms or one Residential Customer Equivalent (RCE). Wholesale transactions are generally done in decatherms (Dth), thousand decatherms (MDth), or million decatherms (MMDth). A million decatherms is a trillion BTU, roughly a billion cubic feet of natural gas. The price of natural gas varies greatly depending on location and type of consumer. In 2007, a price of $7 per 1000 cubic feet () was typical in the United States. The typical caloric value of natural gas is roughly 1,000 BTU per cubic foot, depending on gas composition. This corresponds to around $7 per million BTU or around $7 per gigajoule (GJ). In April 2008, the wholesale price was $10 per 1000 cubic feet ($10/million BTU). The residential price varies from 50% to 300% more than the wholesale price. At the end of 2007, this was $12–$16 per 1000 cubic feet (). Natural gas in the United States is traded as a futures contract on the New York Mercantile Exchange. Each contract is for 10,000 million BTU or . Thus, if the price of gas is $10/million BTU on the NYMEX, the contract is worth $100,000.


Canada

Canada uses metric units, metric measure for internal trade of petrochemical products. Consequently, natural gas is sold by the gigajoule (GJ), cubic meter (m3) or thousand cubic meters (E3m3). Distribution infrastructure and meters almost always meter volume (cubic foot or cubic meter). Some jurisdictions, such as Saskatchewan, sell gas by volume only. Other jurisdictions, such as Alberta, gas is sold by the energy content (GJ). In these areas, almost all meters for residential and small commercial customers measure volume (m3 or ft3), and billing statements include a multiplier to convert the volume to energy content of the local gas supply. A gigajoule (GJ) is a measure approximately equal to half a barrel (250 lbs) of oil, or 1 million BTUs, or of gas. The energy content of gas supply in Canada can vary from depending on gas supply and processing between the wellhead and the customer.


As an asset class for investors

Research conducted by the World Pensions Council (WPC) suggests that large US and Canadian pension funds and Asian and MENA area Sovereign wealth fund, SWF investors have become particularly active in the fields of natural gas and natural gas infrastructure, a trend started in 2005 by the formation of Scotia Gas Networks in the UK by OMERS and Ontario Teachers' Pension Plan.


Adsorbed natural gas (ANG)

Natural gas may be stored by adsorbing it to the porous solids called sorbents. The optimal condition for methane storage is at room temperature and atmospheric pressure. Pressures up to 4 MPa (about 40 times atmospheric pressure) will yield greater storage capacity. The most common sorbent used for ANG is activated carbon (AC), primarily in three forms: Activated Carbon Fiber (ACF), Powdered Activated Carbon (PAC), and activated carbon monolith.


See also

* Associated petroleum gas * Energy transition * Gas oil ratio * Natural gas by country * Peak gas * Power to gas * Renewable natural gas * World energy resources and consumption


References


Further reading

* Blanchard, Charles. ''The Extraction State: A History of Natural Gas in America'' (U of Pittsburgh Press, 2020
online review
* Mincicova V.S. (2021
Possible Medium-Term Scenarios of Dynamics of Russia’s Energy Resource Exports After the Economic Crisis of 2020
In: Shakirova O.G., Bashkov O.V., Khusainov A.A. (eds) Current Problems and Ways of Industry Development: Equipment and Technologies. Lecture Notes in Networks and Systems, vol 200. Springer, Cham. https://doi.org/10.1007/978-3-030-69421-0_92


External links


Global Fossil Infrastructure Tracker
{{DEFAULTSORT:Natural Gas Natural gas, Chinese inventions Fuel gas Fossil fuels