Coal reserves refer to large deposits of coal which, based on geological surveys and engineering studies, are thought to exist to a very high degree of certainty. In addition to the knowledge of their existence, these reserves are also accessible and coal can be produced from them economically. Coal is the most widespread and most abundant fossil fuels. Since so much coal exists, this means that the Earth has significant coal reserves. These reserves are spread all over the globe and mined in every continent except Antarctica. Although the reserves are spread widely, some countries have much more coal than others. It is estimated that the total world reserves amount to around 1012 tonnes of coal. Although the energy contents of the coal vary, rough estimates suggest that this large reserve is equal to around 25 000 exajoules of energy, or around 24 000 quads. About half of the coal reserves are high quality bituminous or anthracite coal.
The United States has more than one-fourth of the worlds known coal reserves, while other major reserves are located in Russia, China, Australia, and India. Most of the worlds coal is buried deep underground and is extracted with traditional mining methods. Where this coal is close to the surface, strip mining is used to expose coal seams. Deep mining is used for more deeply buried coal seams.
One way to determine the size of reserves is known as the reserves/production ratio or R/P. This number represents the number of years that the reserves would last if production and use was continued at the current rate.
Out of all fossil fuel reserves, coal has the largest R/P ratio. Estimates suggest that at current use rates there is around 120 years' worth of coal remaining. However, this ratio needs to be interpreted carefully as this assumes current production levels. Production could increase in the coming years, or decrease as alternative fuels become more prominent. As well, this number doesn't take into account of discoveries of new reserves or developments that allow fuel to be extracted from current resources.
Over 90% of coal in the United States is used for electricity generation, and the coal reserves here have an R/P ratio of over 200 years. Most of the western coal here is strip mined, whereas in the east more than half comes from deep mines.
Chinese coal production has expanded rapidly over the past decade and currently dominates coal production worldwide. Although beneficial for growth and the economy, this results in a significant amount of carbon dioxide emissions. Estimates put the reserves in China at 115 billion tonnes but the R/P ratio is only 38 years due to the extreme rate of use. More than 90% of Chinese mines are deep mines. Although a significant amount of coal is produced in China, the industry is very unsafe with more than 5000 mining related deaths yearly. In addition to this, there are many areas where underground coal fires have been burning uncontrollably.
Russia also produces and exports a significant amount of coal, although these values have significantly dropped as a result of natural gas as an alternative fuel. Although Russia has 19% of the worlds coal reserves and an R/P ratio of over 500 years, much of their reserves are located in remote areas of Serbia, which make production and transport expensive.
India has the fourth largest coal reserves in the world, however much of this coal is extremely poor quality. India imports higher quality coal from Australia. Australia itself has less than 10% of the world's coal reserves, but most of this coal is conveniently located in places that have good rail access and many ports. Most of Australia's exports go to Japan, with some high quality coal going to Europe. Small amounts also go to the Middle East and Asia.
Below is an interactive graph showing what regions have major coal reserves. Note that regions that include the countries that have significant coal reserves, such as Russia contained in Europe and Eurasia, have large amounts of coal compared to other regions which do not have one of these countries.