South Africa's indigenous energy resource base is dominated by coal. Internationally, coal is the most widely used primary fuel, accounting for about 36 percent of the total fuel consumption of the world's electricity production. About 77 percent of South Africa's primary energy needs are provided by coal. This is unlikely to change significantly in the next two decades owing to the relative lack of suitable alternatives to coal as an energy source. Many of the deposits can be exploited at extremely favourable costs and, as a result, a large coal-mining industry has developed. In addition to the extensive use of coal in the domestic economy, about 28 percent of South Africa's production is exported, mainly through the Richards Bay Coal Terminal, making South Africa the fourth-largest coal exporting country in the world. South Africa's coal is obtained from collieries that range from among the largest in the world to small-scale producers. As a result of new entrants, operating collieries increased to 64 during 2004. Of these, a relatively small number of large-scale producers supply coal primarily to electricity and synthetic fuel producers. About 51 percent of South African coal mining is done underground and about 49 percent is produced by open-cast methods. The coal-mining industry is highly concentrated with five companies accounting for 85 percent of saleable coal production. These companies are: . Ingwe Collieries Limited, a BHP Billiton subsidiary; . Anglo Coal; . Sasol; . Eyesizwe; and . Kumba Resources Limited, accounting for 85 percent of the saleable coal production. Production is concentrated in large mines, with 11 mines accounting for 70 percent of the output. South African coal for local electricity production is among the cheapest in the world. The beneficiation of coal, particularly for export, results in more than 65Mt of coal discards being produced every year. About 21 percent of the run-of-mine coal produced is exported, and 21 percent is used locally (excluding power-station coal). The rest is not saleable and is discarded. The remainder of South Africa's coal production feeds the various local industries: . 62 percent is used for electricity generation; . 23 percent for petrochemical industries (Sasol); . 8 percent for general industry; . 4 percent for the metallurgical industry (Mittal); and . 4 percent is purchased by merchants and sold locally or exported. The key role played by South Africa's coal reserves in the economy is illustrated by the fact that Eskom ranks first in the world as a steam coal user and seventh as an electricity generator. Sasol is the largest coal-to-chemicals producer. By international standards, South Africa's coal deposits are relatively shallow with thick seams, which make them easier and, usually, cheaper to mine. At the present production rate, there should be more than 50 years of coal supply left.