| Although [[oil as an energy source|oil]] is, at present, the principal source of energy in the world (easier to produce, transport, store, and use) and [http://www.glossary.oilfield.slb.com/en/Terms/n/natural_gas.aspx gas] is acclaimed as the fuel of the future because it is the cleanest burning of the main sources of energy, coal is, by far, the most abundant and lowest cost [https://www.udemy.com/blog/types-of-fossil-fuels/ fossil fuel] source of energy; coal reserves are 5 times as large as either oil or gas reserves, and coal resources are estimated to be about 17 times the oil resources and 20 times the gas resources. | | Although [[oil as an energy source|oil]] is, at present, the principal source of energy in the world (easier to produce, transport, store, and use) and [http://www.glossary.oilfield.slb.com/en/Terms/n/natural_gas.aspx gas] is acclaimed as the fuel of the future because it is the cleanest burning of the main sources of energy, coal is, by far, the most abundant and lowest cost [https://www.udemy.com/blog/types-of-fossil-fuels/ fossil fuel] source of energy; coal reserves are 5 times as large as either oil or gas reserves, and coal resources are estimated to be about 17 times the oil resources and 20 times the gas resources. |
− | [[file:St54Figure36.JPG|thumb|300px|Coal production.<ref name=Salvador_2005>Salvador, Amos, 2005, Energy-A historical perspective and 21st Century forecast: AAPG Studies in Geology 54, 208 p.</ref>]] | + | [[file:St54Figure36.JPG|thumb|300px|Coal production.<ref name=Salvador_2005>Salvador, A., 2005, Energy-A historical perspective and 21st Century forecast: AAPG Studies in Geology 54, 208 p.</ref>]] |
| Coal is also a versatile source of energy. It can be used for the generation of electricity and as a source of heat; it can be converted to liquid and gaseous fuels; and it is a source of chemical feedstock and metallurgical coke. | | Coal is also a versatile source of energy. It can be used for the generation of electricity and as a source of heat; it can be converted to liquid and gaseous fuels; and it is a source of chemical feedstock and metallurgical coke. |