Difference between revisions of "Fuel" - New World Encyclopedia

Latest revision as of 00:50, 18 October 2022

A filling station in Brazil offers both gasoline (left) and alcohol (right).

Fuel is any material that is burned or altered to obtain energy. Fuel releases its energy either through chemical means, such as combustion, or nuclear means, such as nuclear fission or nuclear fusion. An important property of a useful fuel is that its energy can be stored to be released only when needed, and that the release is controlled in such a way that the energy can be harnessed to produce work.

All known life forms, from microorganisms to humans, depend on and use fuels as their sources of energy. Their cells engage in enzyme-mediated chemical processes collectively called metabolism, which converts energy from food or solar power into a form that can be used to sustain life.^[1] Additionally, humans employ various techniques to convert one form of energy into another, producing usable energy for purposes that go far beyond the energy needs of a human body. The application of energy released from fuels ranges from heating to cooking and from powering weapons to the generation of electricity.

A lump of coal.

Energy sources

All currently known fuels ultimately derive their energy from a small number of sources. Fossil fuels, for example, are thought to have been formed from the remains of living matter, which received its energy from the utilization of solar energy through photosynthesis. Solar energy, in turn, is generated by the thermonuclear fusion process at the core of the Sun. The radioactive isotopes used as fuel to power nuclear plants were formed in supernova explosions.

Chemical

Chemical fuels are substances that generate energy by reacting with substances around them, most notably by the process of oxidation. These substances were the first fuels to be known and used by humans and are still the primary type of fuel used today.

Biofuels

Main article: Biofuel

Wood was one of the first fuels used by humans and is still an important energy source in much of the world.

Biofuel can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from biomass. 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 that was employed by humans is wood. Evidence shows controlled fire was used up to 1.5 million years ago at Swartkrans, South Africa. It is unknown which hominid species first used fire, as both Australopithecus and an early species of Homo were present at the sites.^[2] 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 a relatively low energy density of 10–20 MJ/kg, which is less than half that of gasoline.^[3]

Recently biofuels have been developed for use in automotive transport (for example E10 fuel).

Fossil fuels

Main article: Fossil fuel

Coal rail cars in Ashtabula, Ohio.

Fossil fuels are hydrocarbons, primarily coal and petroleum (liquid petroleum or natural gas), thought to be formed from the fossilized remains of dead plants and animals^[4] by exposure to heat and pressure in the Earth's crust over hundreds of millions of years.^[5] In common parlance, the term fossil fuel also includes hydrocarbon-containing natural resources that are not derived entirely from biological sources, such as tar sands. These latter sources are properly known as mineral fuels.

Modern large-scale industrial development is based on fossil fuel use, which has largely supplanted water-driven mills, as well as the combustion of wood or peat for heat. With global modernization in the twentieth and twenty-first centuries, the growth in energy production from fossil fuels, especially gasoline derived from oil, is one of the causes of major regional and global conflicts and environmental issues. A global movement toward the generation of renewable energy is therefore under way to help meet the increased global energy needs.

The burning of fossil fuels by humans is the largest source of emissions of carbon dioxide, which is one of the greenhouse gases that enhances radiative forcing and contributes to global warming. The atmospheric concentration of CO₂, a greenhouse gas, is increasing, raising concerns that solar heat will be trapped and the average surface temperature of the Earth will rise in response.

Nuclear

Nuclear fuel is any material that is consumed to derive nuclear energy. Technically speaking, this definition includes all matter because any element will under the right conditions release nuclear energy. In practice, the only materials commonly referred to as nuclear fuels are those that will produce energy without being placed under extreme duress.

Fission

Nuclear fuel pellets are used to create nuclear energy.

The most common type of nuclear fuel used by humans is heavy fissile elements that can be made to undergo nuclear fission chain reactions in a nuclear fission reactor; nuclear fuel can refer to the material or to physical objects (for example fuel bundles composed of fuel rods) composed of the fuel material, perhaps mixed with structural, neutron moderating, or neutron reflecting materials. The most common fissile nuclear fuels are ²³⁵U and ²³⁹Pu, and the actions of mining, refining, purifying, using, and ultimately disposing of these elements together make up the nuclear fuel cycle, which is important for its relevance to nuclear power generation and nuclear weapons.

Fusion

Fuels that produce energy by the process of nuclear fusion are currently not utilized by man but are the main source of fuel for stars, the most powerful energy sources in nature. Fusion fuels tend to be light elements such as hydrogen which will combine easily.

In stars that undergo nuclear fusion, fuel consists of atomic nuclei that can release energy by the absorption of a proton or neutron. In most stars the fuel is provided by hydrogen, which can combine together to form helium through the proton-proton chain reaction or by the 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 or nickel-56 nuclei are produced, no further energy can be obtained by nuclear fusion as these have the highest nuclear binding energies.^[6]

Historical use

Scientists think that the first use of fuel was the combustion of wood or sticks by Homo erectus about two million years ago.^[7] Throughout the majority of human history, fuels derived from plants or animal fat were the only ones available for human use. Charcoal, a wood derivative, has been used since at least 6000 B.C.E. for smelting metals. It was only supplanted by coke, derived from coal, as the forests started to become depleted around the eighteenth century. Charcoal briquettes are now commonly used as a fuel for barbecue cooking.^[8]

Coal was first used as a fuel around 1000 B.C.E. in China. With the development of the steam engine in 1769, coal came into more common use as a power source. Coal was later used to drive ships and locomotives. By the nineteenth century, gas extracted from coal was being used for street lighting in London. In the twentieth century, the primary use of coal is for the generation of electricity, providing 40 percent of the world's electrical power supply in 2005.^[9]

Notes

↑ "Metabolism." Encyclopaedia Britannica.
↑ Rincon, Paul. 2004. Bones hint at first use of fire BBC News. Retrieved January 13, 2008.
↑ Elert, Glenn. 2007. Chemical Potential Energy The Physics Hypertextbook. Retrieved January 13, 2008.
↑ Novaczek, Irene. Canada's Fossil Fuel Dependency Elements. Retrieved January 13, 2008.
↑ Fossil fuel EPA. Retrieved January 13, 2008.
↑ Fewell, M.P. 1995. The atomic nuclide with the highest mean binding energy American Journal of Physics. 63:7:653-658. Retrieved January 13, 2008.
↑ Leakey, Richard. 1994. Origin of Humankind. New York, NY: Basic Books. ISBN 0465031358
↑ Hall, Loretta. 2007. Charcoal Briquette How Products Are Made. Retrieved January 13, 2008.
↑ History of Coal Use World Coal Institute. Retrieved January 13, 2008.

References
ISBN links support NWE through referral fees

Barbir, Frano. PEM Fuel Cells: Theory and Practice. Boston, MA: Elsevier Academic Press, 2005. ISBN 0120781425
Pfeiffer, Dale A. Eating Fossil Fuels: Oil, Food And the Coming Crisis in Agriculture. Gabriola Island, BC: New Society Publishers, 2006. ISBN 0865715653
Ratcliff, Brian, et. al. Chemistry 1. Cambridge, UK: Cambridge University Press, 2000. ISBN 0521787785

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Fuel ^history

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[1] "Metabolism." Encyclopaedia Britannica.

[2] Rincon, Paul. 2004. Bones hint at first use of fire BBC News. Retrieved January 13, 2008.

[3] Elert, Glenn. 2007. Chemical Potential Energy The Physics Hypertextbook. Retrieved January 13, 2008.

[4] Novaczek, Irene. Canada's Fossil Fuel Dependency Elements. Retrieved January 13, 2008.

[5] Fossil fuel EPA. Retrieved January 13, 2008.

[6] Fewell, M.P. 1995. The atomic nuclide with the highest mean binding energy American Journal of Physics. 63:7:653-658. Retrieved January 13, 2008.

[7] Leakey, Richard. 1994. Origin of Humankind. New York, NY: Basic Books. ISBN 0465031358

[8] Hall, Loretta. 2007. Charcoal Briquette How Products Are Made. Retrieved January 13, 2008.

[9] History of Coal Use World Coal Institute. Retrieved January 13, 2008.

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@@ Line 1: / Line 1: @@
+{{Copyedited}}{{Images OK}}{{Submitted}}{{Approved}}{{Paid}}
 [[Image:Alcohol fuel pump in Brazil.jpg|thumb|300px|A filling station in Brazil offers both gasoline (left) and alcohol (right).]]
-[[Image:Coal.jpg|150px|thumb|A lump of coal.]]
+'''Fuel''' is any material that is burned or altered to obtain energy. Fuel releases its energy either through chemical means, such as [[combustion]], or nuclear means, such as [[nuclear fission]] or [[nuclear fusion]]. An important property of a useful fuel is that its energy can be stored to be released only when needed, and that the release is controlled in such a way that the energy can be harnessed to produce [[Mechanical work|work]].
+{{toc}}
+All known life forms, from [[microorganism]]s to [[human]]s, depend on and use fuels as their sources of energy. Their [[Cell (biology)|cell]]s engage in [[enzyme]]-mediated chemical processes collectively called ''[[metabolism]]'', which converts energy from [[food]] or solar power into a form that can be used to sustain life.<ref>"Metabolism." ''Encyclopaedia Britannica''.</ref> Additionally, humans employ various techniques to convert one form of energy into another, producing usable energy for purposes that go far beyond the energy needs of a [[human body]]. The application of energy released from fuels ranges from [[heat]]ing to [[cooking]] and from powering [[weapon]]s to the generation of [[Electric power|electricity]].
+[[Image:Coal.jpg|200px|thumb|A lump of coal.]]
-'''Fuel''' is any material that is capable of releasing [[energy]] when its chemical or physical structure is altered. The release of energy takes place either by chemical means, such as by burning the fuel, or nuclear means, such as [[nuclear fission]]* or [[nuclear fusion]]* of the fuel. For a fuel to be useful, it should be possible to store its energy and to release it when needed. Moreover, one should be able to control the release such that the energy can be harnessed to produce [[work]].
+==Energy sources==
+All currently known fuels ultimately derive their energy from a small number of sources. [[Fossil fuel]]s, for example, are thought to have been formed from the remains of living matter, which received its energy from the utilization of [[solar energy]] through [[photosynthesis]]. Solar energy, in turn, is generated by the [[thermonuclear fusion]] process at the core of the [[Sun]]. The [[radioactive]] [[isotope]]s used as fuel to power nuclear plants were formed in [[supernova]] explosions.
-All [[carbon]]-based life forms&mdash;from [[microorganism]]s to [[animal]]s and [[human]]s&mdash;depend on and use fuels as their source of energy. Their [[Cell (biology)|cell]]s engage in [[enzyme]]-mediated chemical processes collectively called ''[[metabolism]]'' that converts energy from [[food]] or the [[Sun]] into a form that can be used to sustain life. <ref>"Metabolism," ''Encyclopaedia Britannica'', retrieved August 17, 2006.</ref> Furthermore, people employ a variety of techniques to convert energy from one form into another, thereby producing energy that can be used for purposes that go well beyond the energy needs of the [[human body]]*. The energy released from fuels can serve a wide range of purposes, such as [[heat]]ing, [[cooking]], [[transportation]], powering [[weapon]]s, and generating [[Electric power|electricity]].
+== Chemical ==
+Chemical fuels are substances that generate energy by reacting with substances around them, most notably by the process of oxidation. These substances were the first fuels to be known and used by [[human]]s and are still the primary type of fuel used today.
-==Extraction of energy from fuel==
+=== Biofuels ===
+{{main|Biofuel}}
+[[Image:Buying fuelwood.jpeg|thumb|right|250px|Wood was one of the first fuels used by humans and is still an important energy source in much of the world.]]
-Chemical energy is stored in the chemical structure of a fuel. When the chemical structure of the fuel is altered, this [[chemical energy]]* is converted into other forms of energy and released. The amount of energy stored in a fuel can be expressed in various ways. For example, "[[fuel value]]*" is used to quantify the [[potential energy]]* of a fuel.
+[[Biofuel]] can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from [[biomass]]. 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.
-The most efficient method for releasing energy from [[fossil fuel]]s is by burning them in [[oxygen]]. In this process, known as ''[[combustion]]'', the fuel reacts with [[oxygen]] and releases energy as [[heat]]. In the fields of [[chemistry]] and [[fire safety]], anything that is capable of [[combustion|burning]] is called ''fuel''. In the case of nuclear energy, certain materials (called ''fissile materials'') are subjected to nuclear reaction.
+Perhaps the earliest fuel that was employed by humans is [[wood]]. Evidence shows controlled fire was used up to 1.5 million years ago at [[Swartkrans]], [[South Africa]]. It is unknown which hominid species first used fire, as both [[Australopithecus]] and an early species of [[Homo (genus)|Homo]] were present at the sites.<ref>Rincon, Paul. 2004. [http://news.bbc.co.uk/1/hi/sci/tech/3557077.stm Bones hint at first use of fire] BBC News. Retrieved January 13, 2008.</ref> 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 a relatively low energy [[density]] of 10&ndash;20 [[Joule|MJ]]/[[Kilogram|kg]], which is less than half that of [[gasoline]].<ref>Elert, Glenn. 2007. [http://hypertextbook.com/physics/matter/energy-chemical/ Chemical Potential Energy] The Physics Hypertextbook. Retrieved January 13, 2008.</ref>
-==Types of fuel==
+Recently biofuels have been developed for use in automotive transport (for example [[E10 fuel]]).
-Theoretically, any fuel can be used as a source of energy. Taking into account economic factors, however, it is practical to choose those fuels that contain large amounts of easily extractable energy. Various types of fuel can be obtained and prepared for consumption relatively inexpensively. Some fuels are chosen because they can be easily transported from their place of production to their place of usage.
-*Natural uses of fuel by organisms focus on conversion of food into energy. Other natural fuel use includes the nuclear fusion that occurs in [[star]]s.
-===Sunlight, air, water, food===
-Living organisms need energy for their own bodily growth and sustenance, and for the various activities they engage in. This energy need is supplied by the sunlight, air, water, and food ([[protein]]s, [[carbohydrate]]s, [[fat]]s, and so forth) available from the environment. The [[Sun]] acts as a source of [[heat]] and [[light]] energy; the air, water, and food can be thought of as fuels that store chemical energy.
-===Wood and peat===
-Wood and peat (when dried) have traditionally been used as fuel for cooking and other heating needs. Wood is derived from [[tree]]s and [[shrub]]s; peat is an accumulation of partially decayed [[vegetation]]* that forms in [[wetland]]s or "peatlands." When burned, the chemical energy stored within wood and peat is converted to heat. In addition, the combustion process produces carbon dioxide, water, and some minor products.
 ===Fossil fuels===
 {{main|Fossil fuel}}
+[[Image:DSCN4524 ashtabulacoalcars e2.jpg|250px|right|thumb|Coal rail cars in Ashtabula, Ohio.]]
-[[Coal]], [[fuel oil]], and [[natural gas]] are generally classified as "fossil fuels," because they are thought to have been formed from the remains of dead plants and animals. These fuels are composed of mainly [[hydrocarbon]]s that, when burned, release [[heat]] energy. Other [[hydrocarbon]]-rich natural fuels not derived from plant or animal sources are also commonly referred to as fossil fuels. A better term for them is "mineral fuels."
+Fossil fuels are [[hydrocarbon]]s, primarily [[coal]] and [[petroleum]] ([[liquid petroleum]] or [[natural gas]]), thought to be formed from the [[fossil|fossilized remains]] of dead plants and animals<ref>Novaczek, Irene. [http://www.elements.nb.ca/theme/fuels/irene/novaczek.htm Canada's Fossil Fuel Dependency] Elements. Retrieved January 13, 2008.</ref> by exposure to heat and pressure in the [[Earth]]'s [[Crust (geology)|crust]] over hundreds of millions of years.<ref>[http://oaspub.epa.gov/trs/trs_proc_qry.navigate_term?p_term_id=7068&p_term_cd=TERM Fossil fuel] EPA. Retrieved January 13, 2008.</ref> In common parlance, the term fossil fuel also includes hydrocarbon-containing [[natural resource]]s that are not derived entirely from biological sources, such as [[tar sands]]. These latter sources are properly known as ''mineral fuels''.
-Fossil fuels have become the dominant [[energy]] resource for the modern world. The utilization of fossil fuels has enabled large-scale industrial development and largely supplanted water-driven mills, as well as the combustion of [[wood]] or [[peat]] for heat.
-[[Solid fuel|Solid fossil fuels]] include [[coal]] and perhaps [[peat]]. All these types of fuel are combustible (they create fire and heat). Coal was burnt by [[steam]] [[rail transport|trains]] to heat water into steam to move parts and provide power. Peat and wood are mainly used for domestic and industrial heating, though peat has been used for [[power generation]], and wood-burning steam [[locomotive]]s were common in times past.
-Non-solid fossil fuels include [[alkanes]] such as [[petroleum]] and [[gas]] (both fuel types have myriad varieties including [[petrol]] (gasoline) and [[natural gas]]). The former is widely used in the [[internal combustion engine]] while both are used in electrical power generation.
-777777777777
-When generating [[electricity]], energy from the [[combustion]] of fossil fuels is often used to power a [[turbine]]. Older generators often used steam generated by the burning of the fuel to turn the turbine, but in newer power plants the gases produced by burning of the fuel turn a [[gas turbine]] directly.
-777777777
-===Hydrogen===
-[[Hydrogen]] also features as an upcoming fuel in the proposed [[hydrogen economy]].  In this case the hydrogen fuel does not occur naturally in usable amounts, and it must be [[Hydrogen production|made]] using other fuels or energy sources.  Hydrogen can react with [[oxygen]] in a [[fuel cell]], producing water (H<sub>2</sub>O) and electrical energy, which then can drive an electric motor to run a car (or a variety of other uses). In this reaction the [[chemical energy]] of the chemicals is converted into [[electrical energy]] via a [[redox]] reaction.
-===Biofuels===
-[[Biofuel]]s such as [[alcohol fuel]] and [[biodiesel]] are made from various kinds of [[biomass]]. The [[biomass]] is plant matter from plants such as [[hemp]], [[maize]], [[sugarcane]], etc, and byproducts from animals such as [[lard]].
-888888888888
-[[Alcohol]] has been used as a fuel in other points in history, but rising [[energy prices]]* and [[environmental problems]]* have led to renewed interest in this fuel.
-The first four aliphatic alcohols&mdash;methanol, ethanol, propanol, and butanol&mdash;are of interest as fuels because they can be synthesized biologically and they have characteristics that permit them to be used in current engines.
-Much attention has been placed on the prospects of using [[ethanol]] as fuel for [[car]]s.
-Alcohol fuels are usually of [[Biological material|biological]] rather than [[petroleum]] sources. When obtained from biological sources, they are sometimes known as '''bioalcohols''' (e.g. '''bioethanol'''). It is important to note that there is no [[Chemistry|chemical]] difference between biologically produced alcohols and that obtained from other sources. However, ethanol that is derived from petroleum should not be considered safe for consumption as this alcohol contains about 5% methanol and may cause blindness or death. This mixture may also not be purified by simple distillation, as it forms an [[Azeotrope|azeotropic]] mixture.
-Bioalcohols are not used in most industrial processes, as alcohols derived from petroleum are usually cheaper in the current economic millieu. Many [[Economics|economists]] argue that this fact illustrates the economic infeasibility of using bioalcohol as a petroleum substitute and argue that government programs that mandate the use of bioalcohol are simply agricultural [[subsidies]]. {{fact}} Lines of counter-argument point out that estimations of feasibility assume the current, status quo infrastructure, which already exists, and therefore is not an initial cost.{{fact}}
+Modern large-scale industrial development is based on fossil fuel use, which has largely supplanted water-driven mills, as well as the combustion of [[wood]] or [[peat]] for heat. With global modernization in the twentieth and twenty-first centuries, the growth in energy production from fossil fuels, especially [[gasoline]] derived from oil, is one of the causes of major regional and global conflicts and environmental issues. A global movement toward the generation of [[renewable energy]] is therefore under way to help meet the increased global energy needs.
-Recent "full up" energy analyses have shown that there is a net energy loss for use of bioalcohols. Use of more optimized crops, elimination of pesticides and fertilizers based on [[petroleum]], and a more rigorous accounting process will help improve the feasibility of bioalcohols as fuels. {{fact}} The "full up" energy analysis does not include the energetic cost of synthesizing crude oil, making the comparison a largely moot point. This merely illustrates that extracting pre-made fuel requires less input energy than producing the fuel from other (potentially renewable) sources of energy.
+The burning of fossil fuels by humans is the largest source of emissions of [[carbon dioxide]], which is one of the [[greenhouse gas]]es that enhances [[radiative forcing]] and contributes to [[global warming]]. The atmospheric concentration of CO<sub>2</sub>, a greenhouse gas, is increasing, raising concerns that solar heat will be trapped and the [[average surface temperature]] of the Earth will rise in response.
+==Nuclear==
+{{main|Nuclear fuel}}
-[[Brazil]] is by far the largest producer of Alcohol Fuel in the world. They typically ferment Ethanol from sugarcane and suger beets.
+Nuclear fuel is any material that is consumed to derive [[nuclear energy]]. Technically speaking, this definition includes all matter because any element will under the right conditions release nuclear energy. In practice, the only materials commonly referred to as nuclear fuels are those that will produce energy without being placed under extreme duress.
-Methanol and ethanol:
+=== Fission ===
-[[Ethanol fuel|Ethanol]] and [[methanol fuel|methanol]] both have advantages and disadvantages over [[fossil fuel]]s, such as [[petrol]] and [[diesel]]. For instance, ethanol can run at a much higher [[compression ratio]] without octane-boosting additives (its [[octane rating]] is 129 as opposed to approximately 91 for ordinary petrol). It burns more completely because ethanol molecules contain oxygen; [[carbon monoxide]] emissions can be 80-90% lower than for fossil-fuelled engines{{fact}}.
+[[Image:Nuclear fuel pellets.jpeg|thumb|right|Nuclear fuel pellets are used to create nuclear energy.]]
-However, ethanol is degrading to some plastic or rubber parts of fuel delivery systems designed to use petrol, and has 37% less energy per litre than petrol. Methanol is even more corrosive and its energy per liter is 55% lower than that of petrol. High compression ratios and  corrosion-resistant materials can overcome these issues, but require extensive engine modification.
+The most common type of nuclear fuel used by humans is heavy [[fissile]] elements that can be made to undergo [[nuclear fission]] [[chain reaction]]s in a [[nuclear reactor|nuclear fission reactor]]; ''nuclear fuel'' can refer to the material or to physical objects (for example fuel bundles composed of [[fuel rod]]s) composed of the fuel material, perhaps mixed with structural, [[neutron moderator|neutron moderating]], or neutron reflecting materials. The most common fissile nuclear fuels are [[U-235|<sup>235</sup>U]] and [[Pu-239|<sup>239</sup>Pu]], and the actions of mining, refining, purifying, using, and ultimately disposing of these elements together make up the [[nuclear fuel cycle]], which is important for its relevance to [[nuclear power]] generation and [[nuclear weapon]]s.
-[[Methanol]] has also been proposed as a fuel of the future. There has been extensive use of [[methanol fuel]] in [[Funny Cars]] for years, and it has been the fuel of [[Indy car]] racing in North America since 1965.
+=== Fusion ===
+Fuels that produce energy by the process of [[nuclear fusion]] are currently not utilized by man but are the main source of fuel for stars, the most powerful energy sources in nature. Fusion fuels tend to be light elements such as [[hydrogen]] which will combine easily.
-[[Ethanol]] is already being used extensively as a [[fuel additive]], but the use of [[ethanol fuel]] alone or as part of a mix with gasoline is increasing. In 2007, the [[Indy Racing League]] will use ethanol as its exclusive fuel, after 40 years of using methanol [http://www.indycar.com/tech/ethanol.php].
+In [[star]]s that undergo [[nuclear fusion]], fuel consists of [[atomic nuclei]] that can release energy by the absorption of a [[proton]] or [[neutron]]. In most stars the fuel is provided by [[hydrogen]], which can combine together to form [[helium]] through the [[proton-proton chain reaction]] or by the [[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 or nickel-56 nuclei are produced, no further energy can be obtained by nuclear fusion as these have the highest nuclear binding energies.<ref>Fewell, M.P. 1995. [http://adsabs.harvard.edu/abs/1995AmJPh..63..653F The atomic nuclide with the highest mean binding energy] ''American Journal of Physics''. 63:7:653-658. Retrieved January 13, 2008.</ref>
-Propanol and Butanol:
+== Historical use ==
-[[Propan-1-ol|Propanol]] and [[butanol]] are considerably less toxic and less volatile than methanol. In particular, butanol has a high [[flashpoint]] of 35 °C, which is a benefit for fire safety, but may be a difficulty for starting engines in cold weather. The concept of flash point is however not directly applicable to engines as the compression of the air in the cylinder means that the temperature is several hundred degrees Celsius before ignition takes place.
+Scientists think that the first use of fuel was the combustion of wood or sticks by ''[[Homo erectus]]'' about two million years ago.<ref>Leakey, Richard. 1994. ''Origin of Humankind''. New York, NY: Basic Books. ISBN 0465031358</ref> Throughout the majority of human history, fuels derived from plants or animal fat were the only ones available for human use. [[Charcoal]], a wood derivative, has been used since at least 6000 B.C.E. for smelting metals. It was only supplanted by [[coke]], derived from coal, as the forests started to become depleted around the eighteenth century. Charcoal briquettes are now commonly used as a fuel for [[barbecue]] cooking.<ref>Hall, Loretta. 2007. [http://www.madehow.com/Volume-4/Charcoal-Briquette.html Charcoal Briquette] How Products Are Made. Retrieved January 13, 2008.</ref>
-The fermentation processes to produce propanol and butanol from [[cellulose]] are fairly tricky to execute, and the Weizmann organism ([[Clostridium acetobutylicum]]) currently used to perform these conversions produces an extremely unpleasant smell, and this must be taken into consideration when designing and locating a fermentation plant. This organism also dies when the butanol content of whatever it is fermenting rises to 7%. For comparison, [[yeast]] dies when the ethanol content of its feedstock hits 14%. Specialized strains can tolerate even greater ethanol concentrations - so-called turbo yeast can withstand up to 16% ethanol [http://running_on_alcohol.tripod.com/].
+Coal was first used as a fuel around 1000 B.C.E. in [[China]]. With the development of the [[steam engine]] in 1769, coal came into more common use as a power source. Coal was later used to drive ships and locomotives. By the nineteenth century, gas extracted from coal was being used for street lighting in [[London]]. In the twentieth century, the primary use of coal is for the generation of [[electricity]], providing 40 percent of the world's electrical power supply in 2005.<ref>[http://www.worldcoal.org/pages/content/index.asp?PageID=107 History of Coal Use] World Coal Institute. Retrieved January 13, 2008.</ref>
-Despite these drawbacks, [[DuPont]], [[British Petroleum]], and [[British Sugar Corporation]] have reportedly started to convert an ethanol plant in the [[United Kingdom]] to produce [[butanol fuel]] from [[sugar beet]]s (and in the future perhaps other starting materials).[http://www.usatoday.com/money/industries/energy/2006-06-20-butanol_x.htm?csp=34]
-* One advantage shared by all four alcohols is [[octane rating]]. [[Biobutanol]] has the additional attraction that its energy per kilogram is closer to gasoline than the other alcohols (while still retaining over 25% higher octane rating).
-888888888888
-===Nuclear fuel===
-In a [[nuclear reactor|nuclear reaction]] a radioactive fuel will undergo [[nuclear fission|fission]]. This provides a useful source of [[energy]] without combustion. Also, in [[star]]s (and our sun), [[hydrogen]] (a gas) is the fuel for the [[nuclear fusion]].
 ==See also==
-*[[Energy density]]
+*[[Alcohol]]
-*[[List of energy topics]]
+*[[Ammonia]]
-*[[Alternative fuels]]
+*[[Battery (electricity)]]
-*[[Solid fuel]]
+*[[Combustion]]
-*[[Liquid fuels]]
-*[[Gas fuel]]
-*[[Alcohol fuel]]
-*[[Biomass]]
-*[[Biofuel]]
-*[[Fuel oil]]
-*[[Fuel poverty]]
 *[[Fossil fuel]]
-*[[Propellant]]
+*[[Fuel cell]]
-*[[Combustion]]
 *[[Hydrocarbon]]
+*[[Hydrogen]]
+*[[Methane]]
 *[[Oxidation]]
-==Footnotes==
+==Notes==
 <references/>
-==Further reading==
+==References==
+* Barbir, Frano. ''PEM Fuel Cells: Theory and Practice''. Boston, MA: Elsevier Academic Press, 2005. ISBN 0120781425
-*[http://www.southerngrease.com Biofuel news and information], ''Southern Grease'', retrieved August 17, 2006.
+* Pfeiffer, Dale A. ''Eating Fossil Fuels: Oil, Food And the Coming Crisis in Agriculture''. Gabriola Island, BC: New Society Publishers, 2006. ISBN 0865715653
-* [http://ec.europa.eu/environment/co2/9994/en.pdf DIRECTIVE 1999/94/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 13 December 1999, relating to the availability of consumer information on fuel economy and CO2 emissions in respect of the marketing of new passenger cars].
+* Ratcliff, Brian, et. al. ''Chemistry 1''. Cambridge, UK: Cambridge University Press, 2000. ISBN 0521787785
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