There are many kinds of fuels that are used today for a variety of uses. Most of them are what we consider "fossil fuels," and the rest harness energy from the sun, wind, and the atom.
Fossil fuels are fuels such as coal, oil, or natural gas formed in the earth from plant or animal remains. They are found worldwide and have been used for centuries. I will give a brief definition of each as follows:
Coal: a black or brownish-black rock formed by the partial decomposition of animal matter in an anaerobic, moisture-free environment and often under extreme pressure and temperature. It is found in veins throughout the world, is extracted or mined, and then crushed or broken into pieces to heat homes, fuel factories and plants, and generate electricity.
Natural Gas: an odorless, invisible gas found naturally in the earth's crust. The decomposition of plant material over millions of years released this gas, which is a mixture of methane gas and other hydrocarbons. It is almost always found in the same location as oil and is drawn off in the drilling operation. But, it can be produced artificially from oil and coal. Used today to fire power plants, heat homes, and various other uses. Highly combustible!
Oil: A thick, black substance (often called petroleum) produced by the decomposition of plants under anaerobic, moisture-free conditions and under extreme pressure and temperatures over millions of years. It is found in pockets under the earth's surface, drilled and pumped to refineries, and refined into numerous products for use in heating, plastics, gasoline and kerosene fuels, and a variety of lubricants.
Other sources of fuels are solar (from the sun), wind generators (from the wind) and nuclear (from the splitting of atoms).
Fuels are materials that by combustion in air or oxygen develop enough heat to be used as sources of energy in technology or in the household.
Classification of fuels by their origin and state of aggregation:
-Natural - wood, charcoal, graphite;
- Artificial - charcoal, coke, petrol, diesel, kerosene, fuel ,oil- cracked gas, acetylene, hydrogen;
- Nuclear fuels - isotopes of heavy elements (uranium, thorium, plutonium).
Solid fuels (wood, charcoal, Coal of land, coke) contain, besides the fuel (carbon and hydrogen), moisture and ash, which reduce the heat output.
Fossil fuels are the remains of plants and animals that lived millions of years ago.
Coal fuels were formed by carbon enrichment of substances of vegetable origin (cellulose, lignin, natural resins, etc..), They contain a higher percentage of carbon than wood, and therefore, they have a higher caloric power.
The use of coal as fuel is relatively recent. For thousands of years, coal was considered a simple black stone. There is an evidence that ancient Britons used coal as fuel, and the Romans learned about its value from them . The first written reference to coal is an Anglo-Saxon Chronicle,from 10th century .
Over the centuries the use of coal has spread for household heating.But the soft coal used, easily obtained, has caused a serious pollution as smoke and soot.
In order to reduce the use of coal, this was heavily taxed and in many places,it's burning was banned, because of hazards of public health.
Consumption of coal grew rapidly in the 1700s,by the time of industrial revolution. Coal was the fuel for steam cars and the coke it was obtained from coal -coke being a rough and porous form of carbon, used in steel making and as fuel.
Liquid fuels are produced, in large part, by processing crude oil. By the atmospheric distillation (primary distillation )there are obtained from crude oil: petrol, kerosene, diesel, fuel oil.
Gasoline is used as fuel for diesel engines and fuel oil is used mainly in domestic heating installations, lately, the oil being processed by vacuum distillation and turned into valuable byproducts (lubricants).