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A fuel is any material that can be made to react with other substances so that it releases energy as
thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concepts, such as the internal energy of a system; heat or sensible heat, which are defined as types of energy transfer (as is ...
or to be used for
work Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking * Work (physics), the product of ...

work
. The concept was originally applied solely to those materials capable of releasing
chemical energy Chemical energy is the potential of 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 having volume. All everyday object ...
but has since also been applied to other sources of heat energy such as
nuclear energy Nuclear energy may refer to: *Nuclear power, the use of sustained nuclear fission or nuclear fusion to generate heat and electricity *Nuclear binding energy, the energy required to split a nucleus of an atom *Nuclear potential energy, the potential ...

nuclear energy
(via
nuclear fission In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which ...

nuclear fission
and
nuclear fusion 400 px, The nuclear binding energy curve. The formation of nuclei with masses up to iron-56 releases energy, as illustrated above. Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei are combined to form one or m ...

nuclear fusion
). The heat energy released by reactions of fuels can be converted into
mechanical energy In physical sciences, mechanical energy is the sum of potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other fact ...
via a
heat engine In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is gove ...

heat engine
. Other times the heat itself is valued for warmth,
cooking Cooking or cookery is the art, science, and craft of using heat to Outline of food preparation, prepare food for consumption. Cooking techniques and ingredients vary widely across the Earth, world, from grilling food over an open fire to using e ...
, or industrial processes, as well as the illumination that accompanies
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
. Fuels are also used in the
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
of
organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multice ...

organism
s in a process known as
cellular respiration 300px, Typical eukaryotic cell Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is a ...

cellular respiration
, where organic
molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms held together by chemical bo ...

molecule
s are oxidized to release usable energy.
Hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , 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 a ...
s and related organic molecules are by far the most common source of fuel used by humans, but other substances, including radioactive metals, are also utilized. Fuels are contrasted with other substances or devices storing potential energy, such as those that directly release
electrical energy Electrical energy is energy derived from electric potential energy or kinetic energy. When used loosely, ''electrical energy'' refers to energy that has been converted ''from'' electric potential energy. This energy is supplied by the combination ...
(such as
batteries Battery may refer to: Energy source * Electric battery, an electrochemical device to provide electrical power ** Automotive battery, a device to provide power to certain functions of an automobile ** List of battery types * Energy storage, inclu ...
and
capacitor A capacitor is a device that stores electrical energy in an electric field. It is a passivity (engineering), passive electronic component with two terminal (electronics), terminals. The effect of a capacitor is known as capacitance. While so ...

capacitor
s) or mechanical energy (such as
flywheel A flywheel is a mechanical device specifically designed to use the conservation of angular momentum so as to efficiently store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia The moment o ...

flywheel
s, springs, compressed air, or water in a reservoir).


History

The first known use of fuel was the
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
of wood or sticks by ''
Homo erectus ''Homo erectus'' (meaning " upright man") is an extinct species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is ofte ...

Homo erectus
'' nearly two million years ago. Throughout most of human history only fuels derived from plants or animal fat were used by humans.
Charcoal Charcoal is a lightweight black carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an elemen ...

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 commonly used as a fuel for
barbecue Barbecue or barbeque (informally BBQ in the UK; Barbie in Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent ...
cooking.
Crude oil Petroleum (), also known as crude oil and oil, is a naturally occurring, yellowish-black liquid found in geological formations beneath the Earth's surface. It is commonly refined into various types of fuels. Components of petroleum are sep ...
was
distilled Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation. Dry distillation is the heating of solid materials to produce gaseous prod ...
by Persian chemists, with clear descriptions given in Arabic handbooks such as those of
Muhammad ibn Zakarīya Rāzi Abū Bakr Muḥammad ibn Zakariyyāʾ al-Rāzī ( ar, أبو بكر محمد بن زكرياء الرازي, also known by his Persian name Rāzī and by his Latinization (literature), Latinized name Rhazes), 864 or 865 – 925 or 935 C ...
. He described the process of distilling crude oil/petroleum into
kerosene Kerosene, paraffin, or lamp oil is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from el, κηρός (''keros'' ...

kerosene
, as well as other hydrocarbon compounds, in his ''Kitab al-Asrar'' (''Book of Secrets''). Kerosene was also produced during the same period from
oil shale Oil shale is an organic-rich fine-grained sedimentary rock Sedimentary rocks are types of Rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at the Earth's surface, followed ...

oil shale
and
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

bitumen
by heating the rock to extract the oil, which was then distilled. Rāzi also gave the first description of a
kerosene lamp A kerosene lamp (also known as a paraffin lamp in some countries) is a type of lighting device that uses kerosene as a fuel. Kerosene lamps have a Candle wick, wick or gas mantle, mantle as light source, protected by a glass chimney or globe; l ...

kerosene lamp
using crude mineral oil, referring to it as the "naffatah". The streets of
Baghdad Baghdad (; ar, بَغْدَاد ) is the capital of Iraq Iraq ( ar, ٱلْعِرَاق, '; ku, عێراق '), officially the Republic of Iraq ( ar, جُمْهُورِيَّة ٱلْعِرَاق '; ku, کۆماری عێراق '), is a ...

Baghdad
were paved with
tar Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal Coal is a combustible black or brownish-bl ...

tar
, derived from petroleum that became accessible from natural fields in the region. In the 9th century,
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 were exploited in the area around modern
Baku Baku (, ; az, Bakı, ) is the capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase or capitals (or more formally ''majuscule'') and sm ...
,
Azerbaijan Azerbaijan (, ; az, Azərbaycan ), officially the Republic of Azerbaijan ( az, Azərbaycan Respublikası ), is a country in the Transcaucasia, Caucasus region of Eurasia. Located at the crossroads of Eastern Europe and Western Asia, it is boun ...
. These fields were described by the Arab geographer Abu al-Hasan 'Alī al-Mas'ūdī in the 10th century, and by
Marco Polo Marco Polo (; ; ; September 15, 1254January 8, 1324) was a Republic of Venice, Venetian merchant, explorer, and writer who travelled through Asia along the Silk Road between 1271 and 1295. His travels are recorded in ''The Travels of Marco P ...

Marco Polo
in the 13th century, who described the output of those wells as hundreds of shiploads. With the energy in the form of
chemical energy Chemical energy is the potential of 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 having volume. All everyday object ...
that could be released through combustion, but the concept development of the
steam engine from Stott Park Bobbin Mill, Cumbria, England A steam engine is a heat engine In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energ ...

steam engine
in the United Kingdom in 1769, coal came into more common use as a power source. Coal was later used to drive ships and
locomotive File:R707-loco-victorian-railways.jpg, upright=1.2, An Victorian Railways R class, R class steam locomotive number R707 as operated by the Victorian Railways of Rail transport in Australia, Australia A locomotive or engine is a rail transport ...

locomotive
s. 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 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 In physics, motion is the phenomenon in which an object changes its positio ...

electricity
, providing 40% of the world's electrical power supply in 2005. Fossil fuels were rapidly 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, but are falling out of favor due to the
global warming 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 event ...

global warming
and related effects that are caused from burning them. Currently the trend has been towards renewable fuels, such as
biofuels Biofuel is fuel that is produced through contemporary processes from biomass, rather than by the very slow geological processes involved in the formation of fossil fuels, such as oil. Since biomass technically can be used as a fuel directly (e.g ...
like alcohols.


Chemical

Chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. 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 (natural fuel)'' and ''secondary (artificial fuel)''. Thus, a general classification of chemical fuels is:


Solid fuel

Solid fuel refers to various types of
solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

solid
material that are used as fuel to produce
energy In physics, energy is the physical quantity, quantitative physical property, property that must be #Energy transfer, transferred to a physical body, body or physical system to perform Work (thermodynamics), work on the body, or to heat it. En ...

energy
and provide
heating File:Pelletkessel in Wohnhaus.JPG, upHot water central heating unit, using wood as fuel A central heating system provides warmth to the number of spaces within a building and optionally also able to heat water heating, domestic hot water from one ...

heating
, usually released through combustion. Solid fuels include
wood Wood is a porous and fibrous structural tissue found in the Plant stem, stems and roots of trees and other woody plants. It is an organic materiala natural composite material, composite of cellulose fibers that are strong in tension and embe ...

wood
,
charcoal Charcoal is a lightweight black carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an elemen ...

charcoal
,
peat Peat (), also known as turf (), is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. The peatland ecosystem covers and ...
,
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata (Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country located mostly in the southern half o ...

coal
,
hexamine fuel tablet A hexamine fuel tablet (or heat tablet, Esbit) is a form of solid fuel Solid fuel refers to various forms of solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a so ...
s, and pellets made from wood (see
wood pellets Pellet fuels (or pellets) are biofuel Biofuel is fuel that is produced through contemporary processes from biomass, rather than by the very slow geological processes involved in the formation of fossil fuels, such as oil. Since biomass technical ...

wood pellets
),
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can ...

corn
,
wheat Wheat is a grass widely Agriculture, cultivated for its seed, a cereal grain which is a worldwide staple food. The Taxonomy of wheat, many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat (''T. aest ...

wheat
,
rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eate ...

rye
and other
grains A grain is a small, hard, dry seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction Reproduction (or procreation or breeding) is the biological pro ...
.
Solid-fuel rocket A solid-propellant rocket or solid rocket is a rocket A rocket (from it, rocchetto, , bobbin/spool) is a projectile that spacecraft, aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmospher ...
technology also uses solid fuel (see
solid propellants Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical r ...
). Solid fuels have been used by humanity for many years to
create fire
create fire
. Coal was the fuel source which enabled the
industrial revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Mainland or continental Europe is the contiguous continent of Europe, excluding its surrounding islands. It can also be ...
, from firing
furnace A furnace, referred to as a heater or boiler in British English, is a heating unit used to heat up an entire building. Furnaces are mostly used as a major component of a central heating system. The name derives from Latin Latin (, or , ) i ...

furnace
s, to running
steam engine from Stott Park Bobbin Mill, Cumbria, England A steam engine is a heat engine In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energ ...

steam engine
s. Wood was also extensively used to run
steam locomotive A steam locomotive is a rail vehicle A railroad car, railcar (American English, American and Canadian English), railway wagon, railway carriage, railway truck, railwagon, railcarriage or railtruck (British English and International Union o ...

steam locomotive
s. Both peat and coal are still used in
electricity generation Electricity generation is the process of generating electric power from sources of primary energy. For electric utility, utilities in the electric power industry, it is the stage prior to its Electricity delivery, delivery (Electric power transmiss ...
today. The use of some solid fuels (e.g. coal) 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
smokeless coal
is often the only solid fuel used. In Ireland, peat
briquette A briquette (; also spelled briquet) is a compressed block of coal dust or other combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_t ...
s are used as smokeless fuel. They are also used to start a coal fire.


Liquid fuels

Liquid fuels are combustible or energy-generating molecules that can be harnessed to create
mechanical energy In physical sciences, mechanical energy is the sum of potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other fact ...
, usually producing
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion (physics), motion. It is defined as the work (physics), work needed to accelerate a body of a given mass from rest to its stated velocity. Having gaine ...
. They must also take the shape of their container; the fumes of liquid fuels are flammable, not the fluids. 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 fuelHydrogen fuel is a zero carbon fuel burned with oxygen. It can be used in fuel cells or internal combustion engines. It has begun to be used in commercial fuel cell vehicles, such as passenger cars, and has been used in fuel cell buses for many ...
(for automotive uses),
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), o ...

ethanol
,
jet fuel Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel 250px, At some airports, underground fuel pipes allow refueling without the need for tank trucks. Trucks carry the necessary hoses and pumping equipment, ...
and
bio-diesel Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with an ...
, which are all categorized as liquid fuels. Emulsified fuels of oil in water, such as
orimulsion Orimulsion is a registered trademark name for a bitumen-based fuel that was developed for industrial use by Intevep, the Research and Development Affiliate of Petroleos de Venezuela SA (PDVSA), following earlier collaboration on oil emulsions with ...
, have been developed as a way to make heavy oil fractions usable as liquid fuels. Many liquid fuels play a primary role in transportation and the economy. Some common properties of liquid fuels are that they are easy to transport and can be handled easily. They are also relatively easy to use for all engineering applications and in home use. Fuels like
kerosene Kerosene, paraffin, or lamp oil is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from el, κηρός (''keros'' ...

kerosene
are rationed in some countries, for example in government-subsidized shops in India for home use. Conventional
diesel Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engine ...
is similar to
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-ignited ...

gasoline
in that it is a mixture of aliphatic hydrocarbons extracted from
petroleum Petroleum (), also known as crude oil and oil, is a #Latent heat of vaporization, naturally occurring, yellowish-black liquid found in geological formations beneath the Earth, Earth's surface. It is commonly refined into various types of fuels. ...

petroleum
. Kerosene is used in
kerosene lamp A kerosene lamp (also known as a paraffin lamp in some countries) is a type of lighting device that uses kerosene as a fuel. Kerosene lamps have a Candle wick, wick or gas mantle, mantle as light source, protected by a glass chimney or globe; l ...

kerosene lamp
s and as a fuel for cooking, heating, and small engines.
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 sometimes a small percentage of carbon dioxide ...

Natural gas
, composed chiefly of
methane Methane (, ) is a chemical compound with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics an ...
, can only exist as a liquid at very low temperatures (regardless of pressure), which limits its direct use as a liquid fuel in most applications.
LP gas Tank cars in a Canadian train for carrying liquefied petroleum gas by rail. Liquefied petroleum gas (LPG or LP gas), is a flammable , Germany Image:Tu braunschweig 750 grad ofen.jpg, 250px, Germany, German test apparatus for determining co ...
is a mixture of
propane Propane () is a three- carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas Natural gas (also called fossil gas; sometimes ju ...

propane
and
butane Butane () or ''n''-butane is an alkane , the simplest alkane In organic chemistry, an alkane, or paraffin (a historical trivial name In chemistry, a trivial name is a nonsystematic name for a chemical substance. That is, the name is not rec ...
, both of which are easily compressible gases under standard atmospheric conditions. It offers many of the advantages of
compressed natural gas Compressed natural gas is a fuel gas made of petrol which is mainly composed of methane (CH4), Gas compression, compressed to less than 1% of the volume it occupies at atmospheric pressure#Standard atmospheric pressure, standard atmospheric pressur ...
(CNG) but is denser than air, does not burn as cleanly, and is much more easily compressed. Commonly used for cooking and space heating, LP gas and compressed propane are seeing increased use in motorized vehicles. Propane is the third most commonly used motor fuel globally.


Fuel gas

Fuel gas is any one of a number of fuels that are
gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an appl ...

gas
eous under ordinary conditions. Many fuel gases are composed of
hydrocarbons 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. (2012) ''Organic Chemistry ...
(such as
methane Methane (, ) is a chemical compound with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics an ...
or
propane Propane () is a three- carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas Natural gas (also called fossil gas; sometimes ju ...

propane
),
hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

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 ...
, or mixtures thereof. Such gases are sources of potential
heat energy In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is go ...
or
light energy Light or visible light is electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ...

light energy
that can be readily transmitted and distributed through pipes from the point of origin directly to the place of consumption. Fuel gas is contrasted with liquid fuels and from solid fuels, though some fuel gases are liquefied for storage or transport. While their gaseous nature can be advantageous, avoiding the difficulty of transporting solid fuel and the dangers of spillage inherent in liquid fuels, it can also be dangerous. It is possible for a fuel gas to be undetected and collect in certain areas, leading to the risk of a
gas explosion A gas explosion is an explosion An explosion is a rapid expansion in volume associated with an extremely vigorous outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Supersonic exp ...
. For this reason,
odorizer An odorizer is a device that adds an odorant to a gas. The most common type is one that adds a mercaptan liquid into natural gas distribution systems so that leaks can be readily detected. Other types have been used for carbon dioxide fire ex ...
s are added to most fuel gases so that they may be detected by a distinct smell. The most common type of fuel gas in current use 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 sometimes a small percentage of carbon dioxide ...

natural gas
.


Biofuels

Biofuel can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from
biomass Biomass is plant or animal material used as fuel to produce electricity or heat. Examples are wood, energy crops and waste from forests, yards, or farms. Since biomass technically can be used as a fuel directly (e.g. wood logs), some people use t ...
. Biomass can also be used directly for heating or power—known as ''biomass fuel''. Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants. Many different plants and plant-derived materials are used for biofuel manufacture. Perhaps the earliest fuel employed by humans is wood. Evidence shows controlled fire was used up to 1.5 million years ago at
Swartkrans Swartkrans is a fossil-bearing cave designated as a South African National Heritage Site, located about from Johannesburg Johannesburg ( , also ; ; Zulu language, Zulu and xh, eGoli), informally known as Jozi, Joburg, or "The City of G ...
, South Africa. It is unknown which hominid species first used fire, as both ''
Australopithecus ''Australopithecus'' (, ; ; singular: australopith) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genera ''Homo'' (which includes modern humans), ''Paranthropus'', and ''Kenyanthropus'' evo ...
'' and an early species of ''
Homo ''Homo'' () is the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, virus ...
'' were present at the sites. As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources. Wood has an
energy density In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through S ...

energy density
of 10–20
MJ
MJ
/ kg. Recently biofuels have been developed for use in automotive transport (for example
bioethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entiti ...
and
biodiesel Biodiesel is a form of diesel fuel Diesel fuel in general is any liquid fuel specifically designed for use in diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine An internal combustion e ...

biodiesel
), but there is widespread public debate about how carbon efficient these fuels are.


Fossil fuels

Fossil fuels are
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , 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 a ...
s, primarily
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata (Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country located mostly in the southern half o ...

coal
and
petroleum Petroleum (), also known as crude oil and oil, is a #Latent heat of vaporization, naturally occurring, yellowish-black liquid found in geological formations beneath the Earth, Earth's surface. It is commonly refined into various types of fuels. ...

petroleum
( liquid petroleum or
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 sometimes a small percentage of carbon dioxide ...

natural gas
), formed from the
fossilized remains
fossilized remains
of ancient plants and animals by exposure to high heat and pressure in the absence of oxygen in the
Earth's crust 350px, Plates in the crust of Earth Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), ...
over hundreds of millions of years. Commonly, the term fossil fuel also includes hydrocarbon-containing
natural resource , Malaysia is an example of undisturbed natural resource. Waterfalls provide spring water for humans, animals and plants for survival and also habitat for marine organisms. The water current can be used to turn turbines for hydroelectric generat ...
s that are not derived entirely from biological sources, such as
tar sands Tar sandstone from United_States.html"_;"title="California,_United_States">California,_United_States_ Oil_sands,_tar_sands,_crude_bitumen,_or_bituminous_sands,_are_a_type_of_unconventional_oil.html" ;"title="United_States_.html" ;"title="Un ...
. These latter sources are properly known as ''mineral fuels''. Fossil fuels contain high percentages of
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 covalent bond, covalent chemical bonds. ...
and include coal, petroleum, and natural gas. They range from volatile materials with low carbon:
hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

hydrogen
ratios like
methane Methane (, ) is a chemical compound with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics an ...
, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like
anthracite Anthracite, also known as hard coal, is a hard, compact variety of coal that has a lustre (mineralogy)#Submetallic lustre, submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of ...

anthracite
coal. Methane can be found in hydrocarbon fields, alone, associated with oil, or in the form of
methane clathrates . 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 A clathrate is a chemical substance A chemical substance i ...
. Fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the Earth's crust over millions of years. This biogenic theory was first introduced by German scholar
Georg Agricola Georgius Agricola (; born Georg Pawer or Georg Bauer; 24 March 1494 – 21 November 1555) was a German Humanist scholar, mineralogist Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal struct ...

Georg Agricola
in 1556 and later by
Mikhail Lomonosov Mikhail Vasilyevich Lomonosov (; russian: Михаил (Михайло) Васильевич Ломоносов, p=mʲɪxɐˈil vɐˈsʲilʲjɪvʲɪtɕ , a=Ru-Mikhail Vasilyevich Lomonosov.ogg; – ) was a Russian polymath A polymath ( e ...

Mikhail Lomonosov
in the 18th century. It was estimated by the
Energy Information Administration The U.S. Energy Information Administration (EIA) is a principal agency of the Federal Statistical System of the United States, U.S. Federal Statistical System responsible for collecting, analyzing, and disseminating energy information to promote s ...
that in 2007 primary sources of energy consisted of petroleum 36.0%, coal 27.4%, natural gas 23.0%, amounting to an 86.4% share for fossil fuels in primary
energy consumption Energy consumption is the amount of energy or power used. Biology In the body, energy consumption is part of energy homeostasis. It derived from food energy. Energy consumption in the body is a product of the basal metabolic rate and the physi ...
in the world. Non-fossil sources in 2006 included
hydroelectric Hydroelectricity, or hydroelectric power, is electricity produced from hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machin ...
6.3%, 8.5%, and others ( geothermal,
solar Solar may refer to: Astronomy * Of or relating to the Sun. ** A solar telescope 175px, The Swedish 1-m Solar Telescope at Roque de los Muchachos Observatory, La Palma in the Canary Islands. A solar telescope is a special purpose telescope used ...

solar
, tidal,
wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, ...

wind
,
wood Wood is a porous and fibrous structural tissue found in the Plant stem, stems and roots of trees and other woody plants. It is an organic materiala natural composite material, composite of cellulose fibers that are strong in tension and embe ...
,
waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance which is discarded after primary use, or is worthless, defective and of no use. A by-product by contrast is a joint product of relatively minor Value (economics), e ...
) amounting to 0.9%. World energy consumption was growing about 2.3% per year. Fossil fuels are
non-renewable resources 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 ...
because they take millions of years to form, and reserves are being depleted much faster than new ones are being made. So we must conserve these fuels and use them judiciously. The production and use of fossil fuels raise environmental concerns. A global movement toward the generation of
renewable energy Renewable energy is energy that is collected from renewable resource File:Global Vegetation.jpg, Global vegetation A renewable resource, also known as a flow resource, is a natural resource which will replenish to replace the portion resour ...
is therefore under way to help meet increased energy needs. The burning of fossil fuels produces around 21.3 billion
tonnes The tonne ( or ; symbol: t) is a Metric_units#Mass, metric unit of mass equal to 1,000 kilograms. It is commonly referred to as a metric ton in the United States. It is equivalent to approximately international avoirdupois pound, pound ...
(21.3
gigatonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass in the International System of Units (SI), the current metric system, having the unit symbol kg. I ...
s) of
carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalent bond, covalently double bonded to two oxygen atoms. It occurs naturally in At ...

carbon dioxide
(CO2) per year, but it is estimated that natural processes can only absorb about half of that amount, so there is a net increase of 10.65 billion tonnes of atmospheric carbon dioxide per year (one tonne of atmospheric carbon is equivalent to 44/12 or 3.7 tonnes of carbon dioxide). Carbon dioxide is one of the
greenhouse gas A greenhouse gas (GHG or GhG) is a gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformat ...
es that enhances
radiative forcing Radiative forcing is the change in energy flux in the atmosphere caused by Climate variability and change, natural or Human impact on the environment#Impacts on climate, anthropogenic factors of climate change as measured by watts / metre2. It is ...
and contributes to
global warming 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 event ...

global warming
, causing the average surface temperature of the Earth to rise in response, which the vast majority of climate scientists agree will cause major
adverse effects An adverse effect is an undesired harmful effect resulting from a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, t ...
. Fuels are a source of energy.


Energy

The amount of energy from different types of fuel depends on the stoichiometric ratio, the chemically correct air and fuel ratio to ensure complete combustion of fuel, and its
specific energy Specific energy or massic energy is energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, it ...

specific energy
, the energy per unit mass. 1  ≈ 0.28 
kWh The kilowatt-hour ( SI symbol: kW⋅h or kW h; commonly written as kWh) is a unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, ...
≈ 0.37  HPh.


Nuclear

Nuclear fuel is any material that is consumed to derive
nuclear energy Nuclear energy may refer to: *Nuclear power, the use of sustained nuclear fission or nuclear fusion to generate heat and electricity *Nuclear binding energy, the energy required to split a nucleus of an atom *Nuclear potential energy, the potential ...

nuclear energy
. Technically speaking, all matter can be a nuclear fuel because any element under the right conditions will release nuclear energy, but the materials commonly referred to as nuclear fuels are those that will produce energy without being placed under extreme duress. Nuclear fuel is a material that can be 'burned' by
nuclear fission In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which ...

nuclear fission
or to derive nuclear energy. ''Nuclear fuel'' can refer to the fuel itself, or to physical objects (for example bundles composed of fuel rods) composed of the fuel material, mixed with structural, neutron moderating, or neutron reflecting materials. Most nuclear fuels contain heavy
fissile In nuclear engineering Nuclear engineering is the branch of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, veh ...
elements that are capable of nuclear fission. When these fuels are struck by neutrons, they are in turn capable of emitting neutrons when they break apart. This makes possible a self-sustaining
chain reaction A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback Positive feedback (exacerbating feedback, self-reinforcing feedback) is a pro ...
that releases energy with a controlled rate in a
nuclear reactor A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclea ...

nuclear reactor
or with a very rapid uncontrolled rate in a
nuclear weapon A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission, fissi ...
. The most common fissile nuclear fuels are
uranium-235 Uranium-235 (235U) is an Isotopes of uranium, isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear fission, fission chain reaction. It is the only f ...

uranium-235
(235U) and
plutonium-239 Plutonium-239 (239Pu, Pu-239) is an isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but differe ...
(239Pu). The actions of mining, refining, purifying, using, and ultimately disposing of nuclear fuel together make up the
nuclear fuel cycle The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission ...

nuclear fuel cycle
. Not all types of nuclear fuels create power from nuclear fission.
Plutonium-238 Plutonium-238 (238Pu) is a radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the sma ...

Plutonium-238
and some other elements are used to produce small amounts of nuclear power by
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

radioactive decay
in
radioisotope thermoelectric generator A radioisotope thermoelectric generator (RTG, RITEG) is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive Radioactive decay (also known as nuclear decay, radi ...
s and other types of atomic batteries. Also, light
nuclide A nuclide (or nucleide, from atomic nucleus, nucleus, also known as nuclear species) is a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state. The word ''nuclide'' was coi ...

nuclide
s such as
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleu ...

tritium
(3H) can be used as fuel for
nuclear fusion 400 px, The nuclear binding energy curve. The formation of nuclei with masses up to iron-56 releases energy, as illustrated above. Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei are combined to form one or m ...

nuclear fusion
. Nuclear fuel has the highest
energy density In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through S ...

energy density
of all practical fuel sources.


Fission

The most common type of nuclear fuel used by humans is heavy
fissile In nuclear engineering Nuclear engineering is the branch of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, veh ...
elements that can be made to undergo
nuclear fission In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which ...

nuclear fission
chain reactions in a ; ''nuclear fuel'' can refer to the material or to physical objects (for example fuel bundles composed of
fuel rod Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission. Most nuclear fuels contain heavy fissile actinide elements that are capable of Fissile mate ...
s) composed of the fuel material, perhaps mixed with structural, neutron moderating, or neutron reflecting materials.


Fusion

Fuels that produce energy by the process of
nuclear fusion 400 px, The nuclear binding energy curve. The formation of nuclei with masses up to iron-56 releases energy, as illustrated above. Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei are combined to form one or m ...

nuclear fusion
are currently not utilized by humans but are the main source of fuel for
star A star is an astronomical object consisting of a luminous spheroid of plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark ...

star
s. Fusion fuels tend to be light elements such as
hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

hydrogen
which will combine easily. Energy is required to start fusion by raising temperature so high all materials would turn into plasma, and allow nuclei to collide and stick together with each other before repelling due to electric charge. This process is called fusion and it can give out energy. In stars that undergo nuclear fusion, fuel consists of
atomic nuclei The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger-Marsden experiments, Geiger–Marsden gold foil experiment. After the d ...
that can release energy by the absorption of a
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
or
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

neutron
. In most stars the fuel is provided by hydrogen, which can combine to form
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
through the proton-proton chain reaction or by the
CNO cycle The CNO cycle (for carbon–nitrogen–oxygen; sometimes called Bethe–Weizsäcker cycle after Hans Albrecht Bethe and Carl Friedrich von Weizsäcker) is one of the two known sets of nuclear fusion, fusion nuclear reaction, reactions by which st ...

CNO cycle
. When the hydrogen fuel is exhausted, nuclear fusion can continue with progressively heavier elements, although the net energy released is lower because of the smaller difference in nuclear binding energy. Once
iron-56 Iron-56 (56Fe) is the most common isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different ...

iron-56
or
nickel-56 Naturally occurring nickel Nickel is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms ...
nuclei are produced, no further energy can be obtained by nuclear fusion as these have the highest nuclear binding energies. The elements then on use up energy instead of giving off energy when fused. Therefore, fusion stops and the star dies. In attempts by humans, fusion is only carried out with hydrogen (isotope of 2 and 3) to form helium-4 as this reaction gives out the most net energy. Electric confinement (
ITER ITER is an international nuclear fusion 400 px, The nuclear binding energy curve. The formation of nuclei with masses up to iron-56 releases energy, as illustrated above. Nuclear fusion is the process by which two or more atoms are combin ...
), inertial confinement (heating by laser) and heating by strong electric currents are the popular methods.


Liquid fuels for transportation

Most transportation fuels are liquids, because vehicles usually require high
energy density In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through S ...

energy density
. This occurs naturally in liquids and solids. High energy density can also be provided by an
internal combustion engine An internal combustion engine (ICE) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, t ...

internal combustion engine
. These engines require clean-burning fuels. The fuels that are easiest to burn cleanly are typically liquids and gases. Thus, liquids meet the requirements of being both energy-dense and clean-burning. In addition, liquids (and gases) can be pumped, which means handling is easily mechanized, and thus less laborious. As there is a general movement towards a low carbon economy, the use of liquid fuels such as hydrocarbons is coming under scrutiny.


See also

*
Alcohol fuel upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain of carbon atoms (R) In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemic ...
*
Alternative fuels Alternative fuels, known as non-conventional and advanced fuels, are any materials or substances that can be used as fuels, other than conventional fuels like; '' fossil fuels'' (petroleum Petroleum (), also known as crude oil and oil, is ...
* Ammonia * Bitumen-based fuel * Cryogenic fuel * Fossil fuel phase-out * Fuel card * Fuel cell * Fuel container * Fuel management systems * Fuel oil * Fuel poverty * Filling station * Hydrogen economy * Hypergolic fuel * List of energy topics * Low-carbon economy * Marine fuel management * Propellant * Recycled fuel * World energy resources and consumption


Footnotes


References

*


Further reading

*  .
Council Directive 80/1268/EEC Fuel consumption of motor vehicles
{{Authority control Fuels, Energy development