A fuel is any material that can be made to react with other substances so that it releases energy as heat energy or to be used for work. The concept was applied to those materials capable of releasing chemical energy but has since been applied to other sources of heat energy such as nuclear energy; the heat energy released by reactions of fuels is converted into mechanical energy via a heat engine. Other times the heat itself is valued for warmth, cooking, or industrial processes, as well as the illumination that comes with combustion. Fuels are used in the cells of organisms in a process known as cellular respiration, where organic molecules are oxidized to release usable energy. Hydrocarbons and related oxygen-containing molecules are by far the most common source of fuel used by humans, but other substances, including radioactive metals, are utilized. Fuels are contrasted with other substances or devices storing potential energy, such as those that directly release electrical energy or mechanical energy.
The first known use of fuel was the combustion of wood or sticks by Homo erectus nearly two million years ago. Throughout most of human history fuels derived from plants or animal fat were only used by humans. Charcoal, a wood derivative, has been used since at least 6,000 BCE for melting metals, it was only supplanted by coke, derived from coal, as European forests started to become depleted around the 18th century. Charcoal briquettes are now used as a fuel for barbecue cooking. Coal was first used as a fuel around 1000 BCE in China. With the energy in the form of chemical energy that could be released through combustion, but the concept development of the steam engine in the United Kingdom in 1769, coal came into more common use as a power source. Coal was used to drive ships and locomotives. By the 19th century, gas extracted from coal was being used for street lighting in London. In the 20th and 21st centuries, the primary use of coal is to generate electricity, providing 40% of the world's electrical power supply in 2005.
Fossil fuels were adopted during the Industrial Revolution, because they were more concentrated and flexible than traditional energy sources, such as water power. They have become a pivotal part of our contemporary society, with most countries in the world burning fossil fuels in order to produce power; the trend has been towards renewable fuels, such as biofuels like alcohols. Chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of combustion. Most of the chemical energy released in combustion was not stored in the chemical bonds of the fuel, but in the weak double bond of molecular oxygen. Chemical fuels are divided in two ways. First, by their physical properties, as a solid, liquid or gas. Secondly, on the basis of their occurrence: primary and secondary. Thus, a general classification of chemical fuels is: Solid fuel refers to various types of solid material that are used as fuel to produce energy and provide heating released through combustion.
Solid fuels include wood, peat, hexamine fuel tablets, pellets made from wood, wheat and other grains. Solid-fuel rocket technology uses solid fuel. Solid fuels have been used by humanity for many years to create fire. Coal was the fuel source which enabled the industrial revolution, from firing furnaces, to running steam engines. Wood was extensively used to run steam locomotives. Both peat and coal are still used in electricity generation today; the use of some solid fuels is restricted or prohibited in some urban areas, due to unsafe levels of toxic emissions. The use of other solid fuels as wood is decreasing as heating technology and the availability of good quality fuel improves. In some areas, smokeless coal is the only solid fuel used. In Ireland, peat briquettes are used as smokeless fuel, they are used to start a coal fire. Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy producing kinetic energy, it is the fumes of liquid fuels.
Most liquid fuels in widespread use are derived from the fossilized remains of dead plants and animals by exposure to heat and pressure inside the Earth's crust. However, there are several types, such as hydrogen fuel, jet fuel and bio-diesel which are all categorized as a liquid fuel. Emulsified fuels of oil-in-water such as orimulsion have been developed a way to make heavy oil fractions usable as liquid fuels. Many liquid fuels play a primary role in the economy; some common properties of liquid fuels are that they are easy to transport, that can be handled easily. They are easy to use for all engineering applications, home use. Fuels like kerosene are rationed in some countries, for example available in government subsidized shops in India for home use. Conventional diesel is similar to gasoline in that it is a mixture of aliphatic hydrocarbons extracted from petroleum. Kerosene is used in kerosene lamps and as a fuel for cooking and small engines. Natural gas, composed chiefly of methane, can only exist as a liquid at low temperatures, which limits its direct use as a liquid fuel in most applications.
LP gas is a mixture of propane and butane, both of which are compressible gases under standard atmospheric conditions. It offers many of the advantages of compressed natural gas (CN
North Karelia is a region in eastern Finland. It borders the regions of Kainuu, Northern Savonia, Southern Savonia and South Karelia, as well as Russia; the city of Joensuu is the capital of North Karelia. North Karelia is renowned among public health officials. In the 1960s Finland led industrialized nations in heart disease mortality rates. In 1972 a long-term project was undertaken; the resulting improvement in public health is still considered remarkable, a model for the rest of the nation. The region of North Karelia is made up of 13 municipalities; the coat of arms of North Karelia is composed of the arms of Karelia. Institutions of higher education in North Karelia include: University of Eastern Finland North Karelia University of Applied Sciences Riveria Vocational Education and Training Results of the Finnish parliamentary election, 2011 in North Karelia: Social Democratic Party 26.4% Centre Party 26.2% True Finns 23.1% National Coalition Party 10.5% Green League 5.4% Left Alliance 4.2% Christian Democrats 2.8% North Karelia Visitkarelia.fi - Information about travel and other fields in North Karelia Video about travelling in North Karelia Pielis.ru – travel information about North Karelia region and City of Joensuu
Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or engine turning a propeller, or less in pump-jets, an impeller. Marine engineering is the discipline concerned with the engineering design process of marine propulsion systems. Manpower, in the form of paddles, sail were the first forms of marine propulsion. Rowed galleys, some equipped with sail played an important early role; the first advanced mechanical means of marine propulsion was the marine steam engine, introduced in the early 19th century. During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 1950s, produce steam to propel warships and icebreakers. Electric motors using electric battery storage have been used for propulsion on submarines and electric boats and have been proposed for energy-efficient propulsion.
Development in liquefied natural gas fueled engines are gaining recognition for their low emissions and cost advantages. Stirling engines, which are more efficient, smoother running producing less harmful emissions than diesel engines, propel a number of small submarines, its design has yet to be upscaled for larger surface ships. Until the application of the coal-fired steam engine to ships in the early 19th century, oars or the wind were the principal means of watercraft propulsion. Merchant ships predominantly used sail, but during periods when naval warfare depended on ships closing to ram or to fight hand-to-hand, galley were preferred for their manoeuvrability and speed; the Greek navies that fought in the Peloponnesian War used triremes, as did the Romans at the Battle of Actium. The development of naval gunnery from the 16th century onward vaulted broadside weight ahead of manoeuvrability. In modern times, human propulsion is found on small boats or as auxiliary propulsion on sailboats.
Human propulsion includes the push pole and pedals. Propulsion by sail consists of a sail hoisted on an erect mast, supported by stays, controlled by lines made of rope. Sails were the dominant form of commercial propulsion until the late nineteenth century, continued to be used well into the twentieth century on routes where wind was assured and coal was not available, such as in the South American nitrate trade. Sails are now used for recreation and racing, although innovative applications of kites/royals, rotorsails, wingsails and SkySails's own kite buoy-system have been used on larger modern vessels for fuel savings; the development of piston-engined steamships was a complex process. Early steamships were fueled by wood ones by coal or fuel oil. Early ships used stern or side paddle wheels; the first commercial success accrued to Robert Fulton's North River Steamboat in US in 1807, followed in Europe by the 45-foot Comet of 1812. Steam propulsion progressed over the rest of the 19th century.
Notable developments include the steam surface condenser, which eliminated the use of sea water in the ship's boilers. This, along with improvements in boiler technology, permitted higher steam pressures, thus the use of higher efficiency multiple expansion engines; as the means of transmitting the engine's power, paddle wheels gave way to more efficient screw propellers. Multiple expansion steam engines became widespread in the late 19th century; these engines exhausted steam from a high pressure cylinder to a lower pressure cylinder, giving a large increase in efficiency. Steam turbines were fueled by coal or fuel oil or nuclear power; the marine steam turbine developed by Sir Charles Algernon Parsons raised the power-to-weight ratio. He achieved publicity by demonstrating it unofficially in the 100-foot Turbinia at the Spithead Naval Review in 1897; this facilitated a generation of high-speed liners in the first half of the 20th century, rendered the reciprocating steam engine obsolete. In the early 20th century, heavy fuel oil came into more general use and began to replace coal as the fuel of choice in steamships.
Its great advantages were convenience, reduced manpower by removal of the need for trimmers and stokers, reduced space needed for fuel bunkers. In the second half of the 20th century, rising fuel costs led to the demise of the steam turbine. Most new ships since around 1960 have been built with diesel engines; the last major passenger ship built with steam turbines was Fairsky, launched in 1984. Many steam ships were re-engined to improve fuel efficiency. One high-profile example was the 1968 built Queen Elizabeth 2 which had her steam turbines replaced with a diesel-electric propulsion plant in 1986. Most new-build ships with steam turbines are specialist vessels such as nuclear-powered vessels, certain merchant vessels where the cargo can be used as bunker fuel. New LNG carriers continue to be built with steam turbines; the natural gas is stored in a liquid state in cryogenic vessels aboard these ships, a small amount of'boil off' gas is needed to maintain the pressure and temperature inside the vessels within operating limits.
The'boil off' gas provides the fuel for the ship's boilers, which provide steam for the tu
An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, provide safe waterways for other boats and ships. Although the term refers to ice-breaking ships, it may refer to smaller vessels, such as the icebreaking boats that were once used on the canals of the United Kingdom. For a ship to be considered an icebreaker, it requires three traits most normal ships lack: a strengthened hull, an ice-clearing shape, the power to push through sea ice. Icebreakers clear paths by pushing straight into frozen-over pack ice; the bending strength of sea ice is low enough that the ice breaks without noticeable change in the vessel's trim. In cases of thick ice, an icebreaker can drive its bow onto the ice to break it under the weight of the ship. A buildup of broken ice in front of a ship can slow it down much more than the breaking of the ice itself, so icebreakers have a specially designed hull to direct the broken ice around or under the vessel; the external components of the ship's propulsion system are at greater risk of damage than the vessel's hull, so the ability of an icebreaker to propel itself onto the ice, break it, clear the debris from its path is essential for its safety.
Ice-strengthened ships were used in the earliest days of polar exploration. These were wooden and based on existing designs, but reinforced around the waterline with double planking to the hull and strengthening cross members inside the ship. Bands of iron were wrapped around the outside. Sometimes metal sheeting was placed at the bows, at the stern, along the keel; such strengthening was designed to help the ship push through ice and to protect the ship in case it was "nipped" by the ice. Nipping occurs when ice floes around a ship are pushed against the ship, trapping it as if in a vise and causing damage; this vise-like action is caused by the force of tides on ice formations. The first boats to be used in the polar waters were those of the indigenous Arctic people, their kayaks are small human-powered boats with a covered deck, one or more cockpits, each seating one paddler who strokes a single or double-bladed paddle. Such boats, of course, have no icebreaking capabilities, but they are light and well fit to carry over the ice.
In the 9th and 10th centuries, the Viking expansion reached the North Atlantic, Greenland and Svalbard in the Arctic. Vikings, operated their ships in the waters that were ice-free for most of the year, in the conditions of the Medieval Warm Period. In the 11th century, in North-Russia started settling the coasts of the White Sea, named so for being ice-covered for over half of a year; the mixed ethnic group of the Karelians and the Russians in the North-Russia that lived on the shores of the Arctic Ocean became known as Pomors. They developed a special type of small one- or two-mast wooden sailing ships, used for voyages in the ice conditions of the Arctic seas and on Siberian rivers; these earliest icebreakers were called kochi. The koch's hull was protected by a belt of ice-floe resistant flush skin-planking along the variable water-line, had a false keel for on-ice portage. If a koch became squeezed by the ice-fields, its rounded bodylines below the water-line would allow for the ship to be pushed up out of the water and onto the ice with no damage.
In the 19th century, similar protective measures were adopted to modern steam-powered icebreakers. Some notable sailing ships in the end of the Age of Sail featured the egg-shaped form like that of Pomor boats, for example the'Fram, used by Fridtjof Nansen and other great Norwegian Polar explorers. Fram was the wooden ship to have sailed farthest north and farthest south, one of the strongest wooden ship built. An early ship designed to operate in icy conditions was a 51-metre wooden paddle steamer, City Ice Boat No. 1, built for the city of Philadelphia by Vandusen & Birelyn in 1837. The ship was powered by two 250-horsepower steam engines and its wooden paddles were reinforced with iron coverings. With its rounded shape and strong metal hull, the Russian Pilot of 1864 was an important predecessor of modern icebreakers with propellers; the ship was built on the orders of shipbuilder Mikhail Britnev. It had the bow altered to achieve an ice-clearing capability; this allowed Pilot to push herself on the top of the ice and break it.
Britnev fashioned the bow of his ship after the shape of old Pomor boats, navigating icy waters of the White Sea and Barents Sea for centuries. Pilot was used between 1864–1890 for navigation in the Gulf of Finland between Kronstadt and Oranienbaum thus extending the summer navigation season by several weeks. Inspired by the success of Pilot, Mikhail Britnev built a second similar vessel Boy in 1875 and a third Booy in 1889; the cold winter of 1870–1871 caused the Elbe River and the port of Hamburg to freeze over, causing a prolonged halt to navigation and huge commercial losses. Carl Ferdinand Steinhaus resused the altered bow Pilot's design from Britnev to make his own icebreaker, Eisbrecher I; the first true modern sea-going icebreaker was built at the turn of the 20th century. Icebreaker Yermak, was built in 1897 at the Armstrong Whitworth naval yard in England under contract from the Imperial Russian Navy; the ship borrowed the main principles from Pilot and applied them to the creation of the first polar icebreaker, able to run over and crush pack ice.
The ship displaced 5,000 tons, its steam-reciprocating engines delivered 10,000 horsepower. The ship was deco
Liquefied natural gas
Liquefied natural gas is natural gas, cooled down to liquid form for ease and safety of non-pressurized storage or transport. It takes up about 1/600th the volume of natural gas in the gaseous state, it is odorless, non-toxic and non-corrosive. Hazards include flammability after vaporization into a gaseous state and asphyxia; the liquefaction process involves removal of certain components, such as dust, acid gases, helium and heavy hydrocarbons, which could cause difficulty downstream. The natural gas is condensed into a liquid at close to atmospheric pressure by cooling it to −162 °C. Natural gas is converted to LNG for transport over the seas where laying pipelines is not feasible technically and economically. LNG achieves a higher reduction in volume than compressed natural gas so that the energy density of LNG is 2.4 times greater than that of CNG or 60 percent that of diesel fuel. This makes LNG cost efficient in marine transport over long distances. However, CNG carrier ships can be used economically up to medium distances in marine transport.
Specially designed cryogenic sea vessels or cryogenic road tankers are used for LNG transport. LNG is principally used for transporting natural gas to markets, where it is regasified and distributed as pipeline natural gas, it can be used in natural gas vehicles, although it is more common to design vehicles to use CNG. LNG's high cost of production and the need to store it in expensive cryogenic tanks have hindered widespread commercial use. Despite these drawbacks, on energy basis LNG production is expected to hit 10% of the global crude production by 2020; the heating value depends on the source of gas, used and the process, used to liquefy the gas. The range of heating value can span +/- 10 to 15 percent. A typical value of the higher heating value of LNG is 50 MJ/kg or 21,500 BTU/lb. A typical value of the lower heating value of LNG is 19,350 BTU/lb. For the purpose of comparison of different fuels the heating value may be expressed in terms of energy per volume, known as the energy density expressed in MJ/litre.
The density of LNG is 0.41 kg/litre to 0.5 kg/litre, depending on temperature and composition, compared to water at 1.0 kg/litre. Using the median value of 0.45 kg/litre, the typical energy density values are 22.5 MJ/litre or 20.3 MJ/litre. The energy density of LNG is 2.4 times greater than that of CNG which makes it economical to transport natural gas by ship in the form of LNG. The energy density of LNG is comparable to propane and ethanol but is only 60 percent that of diesel and 70 percent that of gasoline. Experiments on the properties of gases started early in the seventeenth century. By the middle of the seventeenth century Robert Boyle had derived the inverse relationship between the pressure and the volume of gases. About the same time, Guillaume Amontons started looking into temperature effects on gas. Various gas experiments continued for the next 200 years. During that time there were efforts to liquefy gases. Many new facts on the nature of gases had been discovered. For example, early in the nineteenth century Cagniard de la Tour had shown there was a temperature above which a gas could not be liquefied.
There was a major push in the mid to late nineteenth century to liquefy all gases. A number of scientists including Michael Faraday, James Joule, William Thomson, did experiments in this area. In 1886 Karol Olszewski liquefied the primary constituent of natural gas. By 1900 all gases had been liquefied except helium, liquefied in 1908; the first large scale liquefaction of natural gas in the U. S. was in 1918 when the U. S. government liquefied natural gas as a way to extract helium, a small component of some natural gas. This helium was intended for use in British dirigibles for World War I; the liquid natural gas was not stored, but regasified and put into the gas mains. The key patents having to do with natural gas liquefaction were in the mid-1930s. In 1915 Godfrey Cabot patented a method for storing liquid gases at low temperatures, it consisted of a Thermos bottle type design. In 1937 Lee Twomey received patents for a process for large scale liquefaction of natural gas; the intention was to store natural gas as a liquid so it could be used for shaving peak energy loads during cold snaps.
Because of large volumes it is not practical to store natural gas, as a gas, near atmospheric pressure. However, if it can be liquefied it can be stored in a volume 600 times smaller; this is a practical way to store it but the gas must be kept at −260 °F. There are two processes for liquefying natural gas in large quantities; the first is the cascade process, in which the natural gas is cooled by another gas which in turn has been cooled by still another gas, hence named the "cascade" process. There are two cascade cycles prior to the liquid natural gas cycle; the other method is the Linde process, with a variation of the Linde process, called the Claude process, being sometimes used. In this process, the gas is cooled regeneratively by continually passing it through an orifice until it is cooled to temperatures at which it liquefies; the cooling of gas by expanding it through an orifice was developed by James Joule and William Thomson and is known as th
In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object. Energy is a conserved quantity; the SI unit of energy is the joule, the energy transferred to an object by the work of moving it a distance of 1 metre against a force of 1 newton. Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field, the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, the thermal energy due to an object's temperature. Mass and energy are related. Due to mass–energy equivalence, any object that has mass when stationary has an equivalent amount of energy whose form is called rest energy, any additional energy acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy. For example, after heating an object, its increase in energy could be measured as a small increase in mass, with a sensitive enough scale.
Living organisms require exergy to stay alive, such as the energy. Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy; the processes of Earth's climate and ecosystem are driven by the radiant energy Earth receives from the sun and the geothermal energy contained within the earth. The total energy of a system can be subdivided and classified into potential energy, kinetic energy, or combinations of the two in various ways. Kinetic energy is determined by the movement of an object – or the composite motion of the components of an object – and potential energy reflects the potential of an object to have motion, is a function of the position of an object within a field or may be stored in the field itself. While these two categories are sufficient to describe all forms of energy, it is convenient to refer to particular combinations of potential and kinetic energy as its own form. For example, macroscopic mechanical energy is the sum of translational and rotational kinetic and potential energy in a system neglects the kinetic energy due to temperature, nuclear energy which combines utilize potentials from the nuclear force and the weak force), among others.
The word energy derives from the Ancient Greek: translit. Energeia, lit.'activity, operation', which appears for the first time in the work of Aristotle in the 4th century BC. In contrast to the modern definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness and pleasure. In the late 17th century, Gottfried Leibniz proposed the idea of the Latin: vis viva, or living force, which defined as the product of the mass of an object and its velocity squared. To account for slowing due to friction, Leibniz theorized that thermal energy consisted of the random motion of the constituent parts of matter, although it would be more than a century until this was accepted; the modern analog of this property, kinetic energy, differs from vis viva only by a factor of two. In 1807, Thomas Young was the first to use the term "energy" instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described "kinetic energy" in 1829 in its modern sense, in 1853, William Rankine coined the term "potential energy".
The law of conservation of energy was first postulated in the early 19th century, applies to any isolated system. It was argued for some years whether heat was a physical substance, dubbed the caloric, or a physical quantity, such as momentum. In 1845 James Prescott Joule discovered the generation of heat; these developments led to the theory of conservation of energy, formalized by William Thomson as the field of thermodynamics. Thermodynamics aided the rapid development of explanations of chemical processes by Rudolf Clausius, Josiah Willard Gibbs, Walther Nernst, it led to a mathematical formulation of the concept of entropy by Clausius and to the introduction of laws of radiant energy by Jožef Stefan. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time. Thus, since 1918, theorists have understood that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time.
In 1843, James Prescott Joule independently discovered the mechanical equivalent in a series of experiments. The most famous of them used the "Joule apparatus": a descending weight, attached to a string, caused rotation of a paddle immersed in water insulated from heat transfer, it showed that the gravitational potential energy lost by the weight in descending was equal to the internal energy gained by the water through friction with the paddle. In the International System of Units, the unit of energy is the joule, named after James Prescott Joule, it is a derived unit. It is equal to the energy expended in applying a force of one newton through a distance of one metre; however energy is expressed in many other units not part of the SI, such as ergs, British Thermal Units, kilowatt-hours and kilocalories, which require a conversion factor when expressed in SI units. The SI unit of energy rate is the watt, a joule per second. Thus, one joule is one watt-second, 3600 joules equal one wa
Natural gas is a occurring hydrocarbon gas mixture consisting of methane, but including varying amounts of other higher alkanes, sometimes a small percentage of carbon dioxide, hydrogen sulfide, or helium. It 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 obtained from the sun is stored in the form of chemical bonds in the gas. Natural gas is a occurring hydrocarbon used as a source of energy for heating and electricity generation, it is used as a fuel for vehicles and as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals. Natural gas is called a non-renewable resource. Natural gas is found in deep underground rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates. Petroleum is another fossil fuel found in close proximity to and with natural gas. Most natural gas was created over time by two mechanisms: thermogenic.
Biogenic gas is created by methanogenic organisms in marshes, bogs 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 burnt as flare gas; the World Bank estimates that over 150 cubic kilometers of natural gas are flared or vented annually. Before natural gas can be used as a fuel, 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, butanes and higher molecular weight hydrocarbons, hydrogen sulfide, carbon dioxide, water vapor, sometimes helium and nitrogen. Natural gas is informally referred to as "gas" when compared to other energy sources such as oil or coal. However, it is not to be confused with gasoline in North America, where the term gasoline is shortened in colloquial usage to gas. 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 BCE. 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; the discovery and identification of natural gas in the Americas happened in 1626. In 1821, William Hart dug the first natural gas well at Fredonia, New York, United States, which led to the formation of the Fredonia Gas Light Company; the state of Philadelphia created the first municipally owned natural gas distribution venture in 1836. By 2009, 66 000 km³ had been used out of the total 850 000 km³ of estimated remaining recoverable reserves of natural gas. Based on an estimated 2015 world consumption rate of about 3400 km³ 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 recoverable reserves lasting less as few as 80 to 100 years.
In the 19th century, natural gas was obtained as a by-product of producing oil, since the small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction from the reservoir to the surface, similar to uncapping a soft drink bottle where the carbon dioxide effervesces. Unwanted natural gas was a disposal problem in the active oil fields. If there was not a market for natural gas near the wellhead it was prohibitively expensive to pipe to the end user. In the 19th century and early 20th century, unwanted gas was burned off at oil fields. Today, unwanted gas associated with oil extraction is returned to the reservoir with'injection' wells while awaiting a possible future market or to repressurize the formation, which can enhance extraction rates from other wells. In regions with a high natural gas demand, pipelines are constructed when it is economically feasible to transport gas from a wellsite to an end consumer. In addition to transporting gas via pipelines for use in power generation, other end uses for natural gas include export as liquefied natural gas or conversion of natural gas into other liquid products via gas to liquids technologies.
GTL technologies can convert natural gas into liquids products such as diesel or jet fuel. A variety of GTL technologies have been developed, including Fischer–Tropsch, methanol to gasoline and syngas to gasoline plus. 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, jet fuel and aromatic chemicals directly from natural gas via a single-loop process. In 2011, Royal Dutch Shell's 140,000 barrels per day F–T plant went into operation in Qatar. Natural gas can be "associated", or "non-associated", is found in coal beds, it sometimes contains a significant amount of ethane, propane and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen and hydrogen sulfide must be removed before the natural gas can be transported. Natural gas extracted from oil wells is called casinghead gas (whether or not produced up the a