Fuel

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.

All carbon-based life forms—from microorganisms to animals and humans—depend on and use fuels as their source of energy. Their cells 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. 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 heating, cooking, transportation, powering weapons, and generating electricity.

Extraction of energy from fuel

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.

The most efficient method for releasing energy from fossil fuels 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 burning is called fuel. In the case of nuclear energy, certain materials (called fissile materials) are subjected to nuclear reaction.

Types of 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 stars.

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 (proteins, carbohydrates, fats, 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, derived from trees and shrubs, has long been used as a fuel. It is mainly composed of fibers of cellulose and hemicellulose held together by lignin. When burned, wood produces heat energy, as well as carbon dioxide, water, and some minor products.

Fossil fuels

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 hydrocarbons 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." 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 fossil fuels include coal and perhaps peat. All these types of fuel are combustible (they create fire and heat). Coal was burnt by steam 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 locomotives 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 Fossil fuels are hydrocarbons, primarily coal, fuel oil or natural gas, formed from the remains of dead plants and animals. The theory that hydrocarbons were formed from these remains was first introduced by Mikhail Lomonosov in 1757. In common dialogue, the term fossil fuel also includes hydrocarbon-containing natural resources that are not derived from animal or plant sources. These are sometimes known instead as mineral fuels. 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.

Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth's crust over hundreds of millions of years. [1]

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.

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Other types of fuel

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 made using other fuels or energy sources. Hydrogen can react with oxygen in a fuel cell, producing water (H₂O) 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 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.

Nuclear fuel

In a nuclear reaction a radioactive fuel will undergo fission. This provides a useful source of energy without combustion. Also, in stars (and our sun), hydrogen (a gas) is the fuel for the nuclear fusion.

See also

• Energy density
• List of energy topics
• Alternative fuels
• Solid fuel
• Liquid fuels
• Gas fuel
• Alcohol fuel
• Biomass
• Biofuel
• Fuel oil
• Fuel poverty
• Fossil fuel
• Propellant
• Combustion
• Hydrocarbon
• Oxidation

Further reading

• Biofuel news and information, Southern Grease, retrieved August 17, 2006.
• 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.

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