Fuel

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

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. ^[1] 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 and peat (when dried) have traditionally been used as fuel for cooking and other heating needs. Wood is derived from trees and shrubs; peat is an accumulation of partially decayed vegetation that forms in wetlands 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 article: Fossil fuel

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."

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 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

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 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

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.

The first four aliphatic alcohols—methanol, ethanol, propanol, and butanol—are of interest as fuels because they can be synthesized biologically and their characteristics permit their use in current engines. When obtained from biological sources, they are sometimes called "bioalcohols" (such as bioethanol). Bioalcohols are not used in most industrial processes, as alcohols derived from petroleum are usually cheaper in the current economic millieu.

Ethanol and methanol both have advantages and disadvantages over gasoline and diesel. For instance, they burn more completely and their octane ratings (compression ratios) are higher.

ethanol can run at a much higher compression ratio without octane-boosting additives (its octane rating is 129, compared with approximately 91 for ordinary gasoline). It burns more completely because ethanol molecules contain oxygen; carbon monoxide emissions can be 80-90% lower than for fossil-fuelled engines^{[citation needed]}.

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.

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.

Much attention has been placed on the prospects of using ethanol as fuel for cars.

Many 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. ^{[citation needed]} 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.^{[citation needed]}

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. ^{[citation needed]} 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.

Brazil is by far the largest producer of Alcohol Fuel in the world. They typically ferment Ethanol from sugarcane and suger beets.

Methanol and ethanol: Ethanol and methanol both have advantages and disadvantages over fossil fuels, 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^{[citation needed]}.

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.

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.

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 [1].

Propanol and Butanol: 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.

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 [2].

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 beets (and in the future perhaps other starting materials).[3]

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).

Alcohol fuels are usually of biological rather than petroleum sources. It is important to note that there is no 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 azeotropic mixture.

888888888888

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.

Footnotes

↑ "Metabolism," Encyclopaedia Britannica, retrieved August 17, 2006.

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

Fuel ^history

The history of this article since it was imported to New World Encyclopedia:

History of "Fuel"

Note: Some restrictions may apply to use of individual images which are separately licensed.

[1] "Metabolism," Encyclopaedia Britannica, retrieved August 17, 2006.

[1]