The energy in coal comes from the energy stored by plants that lived hundreds of millions of years ago. For millions of years, dead plants at the bottom of prehistoric swamps were covered by layers of water and dirt, trapping the energy of the dead plants. The heat and pressure from the top layers turned the plant remains into the coal we use today.

The United States produces more than 1 billion tons of coal each year, equivalent to 35 percent of total worldwide demand. Coal is the primary fuel source for electrical power generation in the United States and is used for steel production and other industries. Over the last 30 years, the average price of coal in the United States has varied from a low of $17 per ton to a high of $27 per ton. During this time, coal use has almost tripled, while emissions have been reduced by about one-third.

Advantages
Coal is abundant, particularly in regions that lack significant proven oil and gas reserves. World proven coal reserves are four times that of oil and gas reserves combined, equivalent to 190 years of consumption at current rates. The United States has more than 25 percent of the world's coal reserves, but only 3 percent of the world’s oil and gas reserves.

Coal prices have remained relatively stable while competing fuels, such as natural gas, have become more volatile. Coal can be stored relatively inexpensively, thus supply disruptions are not a major concern. Gasification technology offers the option to convert coal into power, chemicals, substitute natural gas or transportation fuels.

Environmental regulations and implementation of clean-coal technologies have reduced the impact that coal consumption has on the environment.  

Issues
Coal is a non-renewable energy source. Surface mining eliminates the natural contours of the land and can require costly restoration. Underground mining can be disruptive to the surface and requires close attention to reduce safety and health risk exposures for workers. Burning coal produces carbon dioxide, which is a greenhouse gas. Expensive scrubbers must be added to coal-fired power plants to reduce emissions of sulfur dioxide, nitrogen oxides, carbon monoxide, mercury and particulates. (Source: U.S. Department of Energy)