Electricity from Coal
Coal is a fossil fuel formed from the decomposition of organic materials that have been subjected to geologic heat and pressure over millions of years. Coal is considered a nonrenewable resource because it cannot be replenished on a human time frame.
The activities involved in generating electricity from coal include mining, transport to power plants, and burning of the coal in power plants. Initially, coal is extracted from surface or underground mines. The coal is often cleaned or washed at the coal mine to remove impurities before it is transported to the power plant—usually by train, barge, or truck. Finally, at the power plant, coal is commonly burned in a boiler to produce steam. The steam is run through a turbine to generate electricity.
Although power plants are regulated by federal and state laws to protect human health and the environment, there is a wide variation of environmental impacts associated with power generation technologies.
The purpose of the following section is to give consumers a better idea of the specific air, water, solid waste, and radioactive releases associated with coal-fired generation.
When coal is burned, carbon dioxide, sulfur dioxide, nitrogen oxides, and mercury compounds are released. For that reason, coal-fired boilers are required to have control devices to reduce the amount of emissions that are released.
The average emission rates in the United States from coal-fired generation are: 2,249 lbs/MWh of carbon dioxide, 13 lbs/MWh of sulfur dioxide, and 6 lbs/MWh of nitrogen oxides.1
Mining, cleaning, and transporting coal to the power plant generate additional emissions. For example, >methane, a potent greenhouse gas that is trapped in the coal, is often vented during these processes to increase safety.
Water Resource Use
Large quantities of water are frequently needed to remove impurities from coal at the mine. In addition, coal-fired power plants use large quantities of water for producing steam and for cooling. When coal-fired power plants remove water from a lake or river, fish and other aquatic life can be affected, as well as animals and people who depend on these aquatic resources.
Pollutants build up in the water used in the power plant boiler and cooling system. If the water used in the power plant is discharged to a lake or river, the pollutants in the water can harm fish and plants. Further, if rain falls on coal stored in piles outside the power plant, the water that runs off these piles can flush heavy metals from the coal, such as arsenic and lead, into nearby bodies of water. Coal mining can also contaminate bodies of water with heavy metals when the water used to clean the coal is discharged back into the environment. This discharge usually requires a permit and is monitored. For more information about these regulations, visit EPA's Office of Water website.
Solid Waste Generation
The burning of coal creates solid waste, called ash, which is composed primarily of metal oxides and alkali.2 On average, the ash content of coal is 10 percent.3 Solid waste is also created at coal mines when coal is cleaned and at power plants when air pollutants are removed from the stack gas. Much of this waste is deposited in landfills and abandoned mines, although some amounts are now being recycled into useful products, such as cement and building materials.
Land Resource Use
Soil at coal-fired power plant sites can become contaminated with various pollutants from the coal and take a long time to recover, even after the power plant closes down. Coal mining and processing also have environmental impacts on land. Surface mining disturbs larger areas than underground mining.
In the United States, coal consumption in 2003 was just over 1.1 billion tons.4 Coal reserves in the United States stand at 268 billion tons, of which 43 percent are in surface mines. The three major coal-producing states are Wyoming, West Virginia, and Kentucky.5
- U.S. EPA, eGRID 2000.
- U.S. Department of Energy, Energy Efficiency and Renewable Energy Network, Glossary of Energy Terms.
- U.S. Department of Energy, Energy Efficiency and Renewable Energy Network, Energy, Environmental, and Economics Handbook.
- U.S. Department of Energy, Energy Information Administration, Annual Energy Outlook 2005.
- U.S. Department of Energy, Energy Information Administration, Annual Coal Report 2003.