The Origins of Coal

Part of the Climate Change exhibition.

Kenn Kiser/Morguefile
A coal-fired plant.

Coal is a remnant of past life—a sort of fossil—that began as a tangle of plants on the surface of ancient Earth. In the process of photosynthesis, plants use sunlight, water and CO2 to grow, releasing oxygen to the atmosphere. When they die and decay, the carbon in their tissues usually returns to the atmosphere as CO2 or a gas called methane (CH4). But the plants that became coal were buried too fast to decay completely. The carbon they retained was eventually compressed into coal.

When we burn coal today, we are abruptly returning to our atmosphere carbon captured slowly, over tens of millions of years, by ancient organisms.

Side Effects

A typical coal-fired plant produces 6 million tons of CO2 a year. Burning coal also releases heavy metals such as cadmium and mercury, which don't contribute to warming but are environmentally toxic. Coal burning results in more exposure to radiation than nuclear power does, and it emits sulfur dioxide (SO2) and nitrogen oxides (NOx), which cause acid rain.

World's Recoverable Coal Deposits

Earth's coal deposits are vast and are spread around much of the globe. The U.S. once led the world in coal mined per year, but the lead has now passed to China.

U.S.: 251 billion metric tons
Russia: 157 billion metric tons
China: 115 billion metric tons
Brazil: 11 billion metric tons
South Africa: 47 billion metric tons
India: 92 billion metric tons
Western Eurasia: 91 billion metric tons
Australia and New Zealand: 79 billion metric tons