Fuel

 Fuel is any material that is burnt or altered in order 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.

The application of energy released from fuels ranges from heat to cooking and from powering weapons to combustion and generation of electricity.

All currently-known fuels ultimately derive their energy from a small number of sources. Much of the chemical energy produced by life forms, such as fossil fuels, is derived 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 was formed in supernova explosions.

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

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.

Fossil fuels are hydrocarbons, primarily coal and petroleum (liquid petroleum or natural gas), formed from the fossilized remains of dead plants and animals by exposure to heat and pressure in the Earth’s crust over hundreds of millions of years. 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 20th and 21st 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.