A fuel is any combustible matter such as oil, wood, gas or stimulant that is used to generate heat or power, and can be potentially used as an energy source for something such as an energy plant or engine. The term fuel comes from the word feuaile which was used to describe a bundle of firewood. A fuel becomes such, when whatever matter is being used, undergoes a nuclear or chemical reaction, and produces a useful energy. There are many different types of fuels. Nuclear fuels, bio-fuels, fossil fuels, and chemical fuels.
     Nuclear fuels are used to generate nuclear power, which is responsible for much of the world’s energy and electricity. Many ships, both military and civilian, are propelled by nuclear power. The Russians were the first to use a nuclear power plant to generate electricity, and this was in the year 1954. The first operational nuclear generator plant in the U.S., was up and running in December of 1957. The world’s first commercial nuclear power station became operational in Sellafield England, in the year 1956. Nuclear power was a hot button issue, as many feared there would be great danger from exposure to radiation and nuclear waste. This produced a positive effect, as safety and health concerns were widely addressed. This led to measures being taken to protect and ensure the health and welfare of not only those working in the plants directly, but civilians as well.
     Bio-fuels are those, which have been acquired from, or contain biomass.  Biomass is matter taken from living or recently living organisms such as tree matter, garbage, or any of a number of plants. These fuels can be made into a solid, liquid or gas. In the liquid form, these fuels can be used as a diesel substitute in some engines. The liquid is obtained from such sources as vegetable oil waste, and biologically produced alcohols such as ethanol, butanol, and propanol.
     The term fossil fuel refers to a fuel derived from the decomposing remains of plants and animals under extreme heat and pressure. This process has the end result of producing such fossil fuels as coal, petroleum and natural gas. In able to release their stored energy, a fossil fuel must be burned. Obtaining fossil fuels is risky however, because of the threats it poses to our ecosystems. These fuels are collected by mining and drilling, which has the direct result of allowing large amounts of salt water to be brought o the surface. If not properly treated, this salt will ruin the natural habitats it encounter, and causes widespread destruction. New technologies are always being developed to learn more about fossil fuels and renewable resources, and how to conserve our earth while using them.
     Chemical fuels are used most often in internal combustion engines, and are synthetically derived. They are designed to increase the specific impulse of the engine, or increase the heat of the combustion available. One fuel most commonly used for this purpose is liquid hydrogen, this liquid chemical fuel, is used generally in rocket engines.
      Fuels, whether natural or synthetic, are used every day in every area of the world. We need these fuels to keep our world running, and new technologies and ways to use these fuels are being developed daily.