Important Terms from A to Z
Coal is a black or brown sedimentary rock consisting mostly of carbon. Coal occurs in different consistencies – bituminous and anthracite are very firm and almost rock-like, whereas lignite is soft and brittle. All coal is formed from plant remains and contains chemically bound energy that can be released by combustion. Coal has been used as a fuel since the 12th century.
Bituminous and anthracite coal reserves were formed 280 to 345 million years ago, while the lignite deposits are much younger, having been formed 2.5 to 65 million years ago. Both types of coal were created by the carbonization of plant remains. Huge forests covered the continents at the time. Plant remains sank in swamps and bogs. In the absence of air, peat was created, which was covered by sediments. The water content decreased steadily through the various stages from peat to lignite, from lignite to bituminous, and from bituminous to anthracite. During the transition from peat to lignite, about 75% of water is shed. A further 10% is shed during the transition from lignite to bituminous coal, and in its hardest phase, anthracite has a water content of close to 0%.
European deposits of lignite are now located mainly in Poland and Germany (in the Lausitz and the Rhenish lignite deposits). They account for around 84% of total European deposits. Larger, non-European lignite deposits are located in Central Canada, Alaska and Siberia. However, global use of lignite is significantly lower than that of bituminous coal.
Bituminous coal occurs on all continents. By far the largest deposits of this kind of coal are in Siberia, in the Appalachians in the Eastern United States and in South Africa, Australia and China. There are suspected to be even larger deposits in Africa and South America. The largest bituminous coal-producing countries are China, the U.S. and India, which together account for around 73% of global production. In the U.S., bituminous coal is one of the most important domestic energy sources alongside natural gas and crude oil.
Bituminous coal is extracted by open-pit or deep mining depending on the geological conditions. In Germany, lignite is extracted in open-pit mines. This involves enormous land consumption. The number of people employed in coal mining fell from 550,000 in 1957 to around 6,000 currently (see coal industry statistics). Mining capacity will continue to be propped up with subsidies of 1.2 billion a year until 2018.
After extraction, coal can be transported via large dry bulk storage terminals, via barge, ship or rail to domestic or international destinations where it will eventually reach the end-consumer.
As a solid fuel, coal is almost exclusively burned in power plants. Lignite and anthracite are used nearly exclusively for electricity production – except for the 14% of it which is called coking coal. Coking coal is obtained from very low-sulfur coal and is used in the production of coke which is an important part of the integrated steel mill process. Germany covers about 25% (2014) of its primary energy consumption with coal and lignite, with lignite accounting for 24% and bituminous coal for around 18% of gross electricity generation in Germany. The bituminous coal used in Germany is imported because it is cheaper than domestic bituminous coal.
Status: December 2015
All information subject to change. Errors and omissions excepted.