Coal

What is Coal

Coal is a combustible rock consisting mainly of carbon, hydrogen and oxygen with lesser amounts of hydrogen, sulphur and other elements. Some water is always present, as are grains of inorganic matter that form an incombustible residue known as ash.

How Coal is Formed

Coal is formed when accumulated plant material is buried and becomes altered by decay and by various amounts of heat and pressure over millions of years. Layers of coal are interspersed with other sedimentary material, like shale and sandstone, to form coal beds or seams which range in size from less than one millimetre to several metres thick.

Coal Ranks

Coal is classified by rank, which is a measure of the amount of alteration it has undergone during formation. Factors affecting the rank of coal include the length of time involved in its formation, as well as the temperature and amount of pressure exerted upon the material.

Consecutive stages in evolution of rank from an initial peat stage are brown coal (or lignite); sub-bituminous; bituminous coal and anthracite (together known as black coal). Increase in rank is due to a gradual increase in temperature and pressure which results in a decrease in water content and therefore an increase in carbon content. Anthracite, for example, consists of approximately 90% carbon, whereas brown coal may consist of only 50% carbon.

Black Coal

Sub-bituminous coal, bituminous coal and anthracite are collectively known as black coal. Black coal contains a lower percentage of moisture and ash which gives it a higher grading and energy value than brown coal. Black coal produces less greenhouse gas emissions than brown coal because of its composition.

Brown Coal

Brown coal (also known as lignite) is a relatively soft material which has a heating value only about one-quarter of that for black coal. It has a much lower carbon content and a much higher moisture content. Where found near the surface in thick seams, it can be mined economically on a large scale by open-cut methods. Brown coal is mined only in Victoria where almost all of the brown coal extracted is burnt to heat steam-generating boilers in electrical power stations located near the coal mines.

Coal Uses

Coal is not homogenous. Different types of coal are used for different purposes. The higher-energy coals (black coal) have a greater proportion of carbon and a lower proportion of ash and moisture, giving them a superior quality and value. Coal plays a fundamental role in providing energy for daily human activities.

Black coal is principally used in power stations to generate electricity. When coal is used for this purpose it is referred to as thermal coal, also known as energy coal or steaming coal. Black coal is also used in coke-making and, when used in this manner, is referred to as coking coal or metallurgical coal. Coke is a porous solid composed mainly of carbon and ash. Good quality coke is hard, has a high crushing strength and is mainly used in blast furnaces that produce iron. This strong, heavy coking coal is expensive and is only produced in Australia and Canada.

Pulverised Coal Injection (PCI) coal is used in blast furnaces as a way of lowering operating costs and extending the life of coke ovens. Black coal is also used as a heat source to make cement and for various other industrial purposes.

Coal in NSW

In 2010-11, NSW produced a record 205 million tonnes (Mt) of raw coal, yielding 157Mt of saleable coal. Coal accounts for most of the mining activity in NSW and continues to be a major employer in NSW. There are an estimated 27,995 people directly employed in coal mines across NSW. 

NSW has over 16.64 billion tonnes of economic recoverable coal resources. Coal reserves are contained within some 60 operating mines and colliery holdings and more than 30 development proposals.

The coalfields of the Sydney-Gunnedah Basin contain almost all of the coal resources in NSW, with smaller quantities in the Gloucester and Oaklands Basin.

In 2010-11, Asia continued to be the major market for NSW coal, with the major customers being Japan, Republic of Korea, Taiwan and China.

89% of the total electricity needs in NSW are met with locally mined thermal coal. 

Relevant Links

For more information, please visit the Where We Mine section of the website.

For more information on coal mining, please visit Underground COAL.

"Coal and the Commonwealth" is an independent study commissioned by Peabody Energy and authored by University of Queensland experts which includes research on the historical, social and economic contribution of coal in Australia.