Coal is an abundant fuel source that is relatively inexpensive to produce and convert to useful energy. However, producing and using coal impacts the environment.

Impacts of coal mining

Surface mines (sometimes called strip mines) are the source of about 65% of the coal that is mined in the United States. These mining operations remove the soil and rock above coal deposits, or seams. The amount of coal produced at a surface mine is determined by the area of land being mined at the surface and the thickness of the coal deposit. For example, in Wyoming's Powder River Basin where coal deposits are close to the surface and may be up to 70 feet thick, one acre of land may produce more than 100,000 tons of coal.

Mountaintop removal and valley fill mining has affected large areas of the Appalachian Mountains in West Virginia and Kentucky. In this form of coal extraction, the tops of mountains are removed using explosives. As a result of this technique, the landscape is changed, and streams may be covered with rock and dirt. The water draining from these filled valleys may contain pollutants that can harm aquatic wildlife downstream. Although mountaintop mining has existed since the 1970s, its use became more widespread and controversial beginning in the 1990s.

U.S. laws require that dust and water runoff from areas affected by coal mining operations must be controlled, and laws require that the area has to be reclaimed close to its original condition.

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Some electric power plants use scrubbers (flue gas desulfurization equipment) to reduce the amount of sulfur exiting their smokestacks. The power plants use electrostatic precipitators or baghouses to remove particulates and heavy metals from the smoke.

Underground mines have less of an impact on the environment compared to surface mines. The largest impact of underground mining may be the methane gas that must be vented out of mines to make the mines a safe place to work. Methane is a strong greenhouse gas, meaning that on an equal-weight basis its global warming potential is much higher than other greenhouse gases. In 2013, methane emissions from underground coal mining accounted for about 9% of total U.S. methane emissions and 1% of total U.S. greenhouse gas emissions (based on global warming potential). Some mines capture and use or sell the methane extracted from mines. Surface mines contributed about 2% of total U.S. methane emissions. Learn more about greenhouse gas emissions.

The ground above mine tunnels can also collapse, and acidic water can drain from abandoned underground mines.

Emissions from burning coal

In the United States, most of the coal consumed is used as a fuel to generate electricity. Burning coal produces emissions that adversely affect the environment and human health.

There are several principal emissions resulting from coal combustion:

  • Sulfur dioxide (SO2), which contributes to acid rain and respiratory illnesses
  • Nitrogen oxides (NOx), which contribute to smog and respiratory illnesses
  • Particulates, which contribute to smog, haze, and respiratory illnesses and lung disease
  • Carbon dioxide (CO2), which is the primary greenhouse gas emission produced from the burning of fossil fuels (coal, oil, and natural gas)
  • Mercury and other heavy metals, which have been linked to both neurological and developmental damage in humans and other animals
  • Fly ash and bottom ash, which are residues created when coal is burned at power plants. In the past, fly ash was released into the air through the smokestack, but laws now require that most emissions of fly ash be captured by pollution control devices. In the United States, fly ash is generally stored near power plants or placed in landfills. Pollution leaching from ash storage and landfills into groundwater and the rupture of several large impoundments of ash are environmental concerns.

Reducing the environmental impacts of coal use

The Clean Air Act and the Clean Water Act require industries to reduce pollutants released into the air and water.

Industry has found several ways to reduce sulfur, NOx, and other impurities from coal. Industry has also found more effective ways of cleaning coal after it is mined, and coal consumers have shifted toward greater use of low sulfur coal.

Power plants use flue gas desulfurization equipment, also known as scrubbers, to clean sulfur from the smoke before it leaves their smokestacks. In addition, industry and the U.S. government have cooperated to develop technologies that can remove impurities from coal or that can make coal more energy-efficient so less needs to be burned.

Equipment intended mainly to reduce SO2, NOx, and particulate matter can also be used to reduce mercury emissions from some types of coal. Scientists are also working on new ways to reduce mercury emissions from coal-burning power plants.

Research is underway to address emissions of carbon dioxide from coal combustion. Carbon capture separates CO2 from emissions sources and recovers it in a concentrated stream. The CO2 can then be sequestered, which puts CO2 into storage, possibly underground, where it will remain permanently.

Reuse and recycling can also reduce coal’s environmental impact. Land that was previously used for coal mining can be reclaimed and used for airports, landfills, and golf courses. Waste products captured by scrubbers can be used to produce products like cement and synthetic gypsum for wallboard.