Definition and Need

What is clean coal?

The phrase “clean coal” is used to describe a new generation of energy processes and technologies that strive to reduce the harmful environmental impacts of coal mining and coal combustion, so that coal can continue to play a part in the world’s clean energy future. In the U.S., the Department of Energy (DOE) supports research to develop technologies that make coal cleaner, such as coal gasification, advanced coal-to-energy conversion technologies, advanced emissions control systems, and carbon capture, utilization, and storage (CCUS) -  also referred to as carbon capture, utilization, and sequestration.[1] See the Technologies page of this portal for a detailed discussion of these and other clean coal processes.

Why we need clean coal initiatives

Both the U.S. Environmental Protection Agency (EPA) and the U.S. Energy Information Administration (EIA) report that the processes of coal mining and coal combustion are harmful to the environment and human health, and burning coal contributes to climate change. [2] [3]

For most coal applications, it first has to be removed from the earth via surface mines (aka strip mines) or through mountaintop removal/valley fill mining, both of which can harm the environment. Surface mines - the source of almost 65% of the coal mined in the U.S. in 2020 - strip away soil and rock above coal deposits, or seams that are close to the surface. Wyoming's Powder River Basin contains the largest surface mines in the U.S. [4]

Mountaintop removal and valley fill mining has impacted large areas of the Appalachian region, particularly in West Virginia and Kentucky. To extract coal, mountaintops are removed using explosives, changing the landscape, and often covering streams with rock and dirt. Polluted water draining from these filled valleys can harm fish and other aquatic wildlife downstream, as well as the animals and humans that consume them. [5]

EIA notes that, while underground mines generally affect the landscape less than surface mines, the ground above mine tunnels can collapse, acidic water can drain from abandoned underground mines, and methane gas that occurs in coal deposits can explode if it concentrates in underground mines. [6]

Both operating and abandoned coal mines can emit methane and heat-trapping gases, also known as greenhouse gases (GHG). According to EIA, methane emissions from coal mining and abandoned coal mines accounted for about 8% of total U.S. methane emissions in 2019 and about 1% of total U.S. GHG. [7]

Mined coal is often burned for heat or electricity generation, which can result in several dangerous emissions, as described by EIA:

  • 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 produced from burning 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 power plants burn coal … laws now require that most emissions of fly ash be captured by pollution control devices. In the United States, fly ash and bottom ash are generally stored near power plants or placed in landfills. [8]

Carbon dioxide (CO2) is of concern, as it is a heat-trapping gas (greenhouse gas) that warms the planet, leading to climate change. CO2 is released into the atmosphere by extracting and burning fossil fuels, such as coal, oil, and natural gas. According to NASA and NOAA, human activities have raised the atmosphere’s carbon dioxide content by 50% in less than 200 years, causing the planet to warm rapidly. [9]

In 2021, only 22% of U.S. electricity was generated from coal [10]. Although coal consumption has declined considerably in the U.S. (U.S. coal consumption peaked in 2007 [11]), there are still coal-fired power plants and regions of the U.S. that depend on them for energy. In addition to utility plants, many industries and businesses have coal-fired power plants to generate electricity and heat for their own use. For example, the concrete and paper industries burn large amounts of coal to produce heat, and the steel industry uses coal coke to smelt iron ore into iron to make steel, which requires the high temperatures created by burning coal coke. Coal is also used to produce synthetic natural gas, called syngas, which can be used to produce electricity and hydrogen. The Great Plains Synfuels Plant in North Dakota converts coal into syngas [12] Electric power is by far the largest coal application, as illustrated by EIA:

Source: U.S. Energy Information Administration [13]

While coal as an energy source has declined considerably in the U.S., coal is also a U.S. export product that helps with trade imbalances. In 2021, the U.S. exported about 15% of its coal production to 83 different countries. About 58% of U.S. coal exports went to five countries, including 15% exported to China. [14

Source: U.S. Energy Information Administration [15]

So, coal is both a domestic energy source and an export product, as well as a source of employment in some regions of the USA. But “clean coal” is a controversial concept. Some consider the phrase “clean coal” to be an oxymoron (meaning there is no way to utilize coal that doesn’t damage the environment and the health of citizens), while others see it as a concept worth exploring, due to the reality that many regions of the world depend on coal as an important energy source. Clean coal advocates see it as a chance to revitalize the coal industry in the U.S. and a chance to develop profitable new technologies that are exportable to coal reliant regions in Africa and Asia. Proponents describe clean coal as an unattainable dream, based on technologies that, if successful, will never be cost effective. That, of course, will depend on what happens to the availability and costs of other energy sources going forward.

While the amount of coal that exists worldwide is difficult to estimate because it is buried underground, EIA reports that the U.S. is the top country in the world in terms of proved recoverable reserves of coal. [16]

Source: U.S. Energy Information Administration [17]

While the Nation’s ultimate goal is to reach net zero CO2 emissions by 2050 by replacing fossil-based energy with renewable clean energy sources such as solar, wind, water, geothermal, bioenergy, and nuclear, the near term goals include finding ways to make fossil fuels such as coal cleaner and safer. [18] This is more important than ever in 2022 as we see coal burning power plants that were shuttered reopen in Europe in response to the energy crisis brought on by the Russian invasion of Ukraine. As energy security and resilience is linked closely to a country’s national and economic security, nations may have to consider keeping coal as a backup power source. So, the cleaner coal can become, the better.

Updated November 2022, Tina Allen