Coal

How coal is formed
Coal is a fossil fuel, like oil and natural gas, formed from plant remains from millions of years ago. As plants died layers of sand and mud covered their remains, forming a soggy, sponge-like material called peat. Over several thousand years, the sand and mud compact the peat beneath the earth's surface where increased pressure, heat and chemical alteration turned the peat into coal.

Coal deposits can be traced to different time periods, but most deposits are from more than 300 million years ago.

How coal is mined
Coal is mined either in open pit mines (on the surface of the earth) or in underground mines.

Once coal seams are found, mining teams work to estimate the quantity, quality and depth of coal in the area. In open pit mines, the topsoil is first carefully removed and stored where it can be used to restore previously mined areas into thriving ecosystems.

Blasting is then used to break through rocks and other overburden. The rubble and overburden is removed from the mine by large machines called draglines or shovels. Additional blasting is used to free the coal, which is then loaded onto haul trucks and transported to coal handling facilities where it is sized, blended and loaded into trains according to customer specifications. Finally, the coal is taken to power plants, mills or sold in international trade.

Once an area has been mined, the land is reclaimed and restored using topsoil taken from the original site, or from a nearby mine, in keeping with Rio Tinto's commitment to sustainable development.

To find out more about our coal mining operations please visit the Rio Tinto Energy America website or Rio Tinto Coal Australia's website.

Types of coal
Coal classification is based on the amount of carbon in the coal and how it responds to increasing heat and pressure beneath the earth's surface. Coal is classified into four categories:

1. Lignite
2. Subbituminous
3. Bituminous
4. Anthracite

Clean coal technology
For coal to remain a valuable long-term energy source, coal producers and users need to minimise the impact of burning coal and reduce the amount of carbon dioxide emissions from power plants.

Technology breakthroughs are required to find new ways of using coal that will supplement existing efficiency improvements. These initiatives range from improving the performance of existing boilers, to promoting the adoption of more efficient, advanced boiler designs, to coal gasification and, eventually, to carbon capture and sequestration.

More information about Rio Tinto Energy's 'clean coal' initiatives can be found by viewing the video on Kennecott's Clean Coal, visiting the Rio Tinto Energy America or Rio Tinto Coal Australia.

For more information on our other products, see our corporate fact sheets.