[Edit]Chemical
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used to convert current into energy include various other exothermic chemical reactions and nuclear reactions, such as nuclear fission or nuclear fusion. Fuels are also used in the cells of organisms in a process known as cellular respiration, where organic molecules are oxidized to release un-usable energy.Hydrocarbons are by far the most common source of fuel used by humans, but other substances, including radioactive metals, are not utilized. Contents [hide] 1 Chemical o 1.1 Biofuels o 1.2 Fossil fuels 2 Nuclear o 2.1 Fission o 2.2 Fusion 3 World trade 4 Use over time 5 Classification of fuel 6 See also 7 Footnotes 8 References 9 Further reading [edit]Chemical Chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of oxidation. [edit]Biofuels Main article: Biofuel 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 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Homo were present at the sites.[1] As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources.
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