What Is Clean Coal Technology? Overview, History, Carbon Emissions

Is "clean coal" a climate solution or an oxymoron?

A carbon capture test unit at the Longanet coal plant in Scotland

Jeff J Mitchell / Getty Images

“Clean coal” was once, for some, a promising way to reduce toxic pollutants and carbon emissions in coal production when better options were costlier and less widely available. For others, “clean coal” has always been an oxymoron. Today, new technologies promise to make coal cleaner—yet no matter how “clean” coal becomes, it will still be dirtier, costlier, and less renewable than wind, solar, and other truly clean sources of energy.

The Rise of Dirty Coal

Coal has been at the heart of the industrial age since James Watt perfected the steam engine in 1776. By 1850, nearly all (98%) of Great Britain's energy was provided by coal, as Britain became the workshop of the world. The United States soon followed suit: By 1900, 71% of America's energy came from coal, but not without cost.

According to the U.S. Mine Safety and Health Administration, there were 104,895 fatalities from coal mining and other coal-related activities in the United States between 1900 and 2020. Coal also fueled the 19th-century growth of cloth factories, which increased the demand for Southern cotton and, in turn, quadrupled the number of enslaved people in the United States.

Young boys at work at the troughs used for cleaning coal at a pit in Bargoed, South Wales.
“Cleaning coal” used to mean picking out impurities or foreign objects by hand.

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Burning coal releases soot, carbon monoxide, sulfur dioxide, nitrogen oxides, mercury, and a number of volatile organic compounds (VOCs) harmful to plants and animals alike. Coal is the most carbon-dense of all fossil fuels, which is why burning it makes it by far the dirtiest, releasing more carbon dioxide into the atmosphere by mass than any other fuel.

According to the U.S. Energy Information Administration, coal represents only 12% of all energy consumption in the United States, yet it produces 21% of energy-related CO2 emissions. In the electricity sector, coal produces 58% of all CO2 emissions, despite producing only 26% of the U.S.'s electricity.

Globally, burning coal accounts for 29% of all energy-related greenhouse gas emissions, larger than any other single source. Cleaning up coal would go a long way toward improving human health and reaching the climate goals of the Paris Agreement. Eliminating coal altogether would do even more.

The Emergence of “Clean Coal”

Efforts to create cleaner coal technology arose in an era when coal was by far the single largest source of the world's energy but also when concerns about coal burning were focused on acid rain rather than global warming.

The U.S. Department of Energy started its Clean Coal Technology Demonstration Program in 1986, with a goal to reduce emissions of particulate matter, sulfur dioxide, and nitrogen oxides, key contributors to acid rain. The programs innovations are credited with reducing NOx emissions from coal plants by 82%, SOx emissions by 88%, and particulate matter emissions by 96%, even as coal use increased by 183% between 1970 and 2008.

In the 2010s, the meaning of “clean coal” changed to include addressing CO2 emissions after the U.S. Environmental Protection Agency declared carbon dioxide and other greenhouse gases pollutants in 2009, and especially when the Obama Administration launched its Climate Action Plan, shifting the focus of the Clean Coal Technology Program to carbon capture, use, and storage (CCUS). It is now called the Office of Clean Coal and Carbon Management to emphasize the role that carbon capture plays in the program.

Coal Embraces Carbon Capture

Along with the oil and gas sectors, leaders of the world's coal industry promote “high efficiency, low emissions” (HELE) coal plants with carbon capture technologies as ways to continue burning fossil fuels in a carbon-neutral manner.

The Hazelwood coal plant in Australia, for example, long called one of the world's most polluting coal-fired power station, was scheduled to be decommissioned in 2009 because of its high CO2 emissions, but the plant was able to postpone its closure until 2031 by beginning a carbon capture and storage pilot program, extracting CO2 from its smokestacks and turning it into calcium carbonate.

But faced with rising costs and competition from natural gas and renewable energy sources, the Hazelwood plant closed in 2016. In July 2021, developers proposed a wind farm overlooking the closed coal plant. Still today, the promise of "clean coal" has yet to bear fruit.

The Hazelwood coal fired power station in the Latrobe Valley, Victoria, Australia
Even CCUS couldn't save the Hazelwood coal plant.

Ashley Cooper/Construction Photography/Avalon/Getty Images

The International Energy Agency's Energy Technology Perspectives 2020 described carbon capture and storage as “the only group of technologies that contributes both to reducing emissions in key sectors directly and to removing CO2 to balance emissions that cannot be avoided.” The key to CCUS is to make it cost-effective. As the IEA's report notes, “markets alone will not turn CCUS into the clean energy success story it must become,” which is why both the U.S. administration and the European Union are committed to helping bring costs down.

As with other areas in clean energy, government support might allow initially costly technologies to become mature and efficient enough to be marketable. Without that economic viability, “clean coal” is indeed an uneconomical contradiction in terms.

Coal Death Watch

In order to meet the goals of the Paris Climate Accord, coal will need to fall by an annual rate of 11% every year until 2030. Recent projections estimate that 89% of available coal must remain in the ground if we are to have a 50% chance of reaching the target of remaining under 1.5 degrees C warming. CCUS will need to play a role in the attempt to keep from overheating the planet, but it will need to do so without keeping coal plants alive.

While advanced industrial nations continue to move away from coal, it remains an affordable source of energy for many developing economies. It still provides 33.8% of the world's electricity—the largest single source, according to the nonprofit campaign Ember's Global Electricity Review 2021.

Yet global coal generation is falling. China was the sole country in the world to expand its coal production in 2020—by 2%. Worldwide, coal production fell by 4% in 2020, while wind and solar together expanded by 15%.

Wind turbines spin to produce electricity as steam rises from cooling towers at Jaenschwalde, Germany.
In Germany, renewable energy made coal mining unprofitable even before coal subsidies were cut in 2018.

Sean Gallup/Getty Images

In the United States, coal production peaked in 2008 and continues to decline. In April 2019, renewable energy sources produced more electricity than coal for the first time. It now costs more to keep many an existing coal plant running than it is to install a new solar power plant. And once installed, solar energy has near-zero marginal costs (it costs nearly nothing to operate), meaning it out-competes coal in energy markets.

This is why 80% of coal plants in the United States are either slated to retire by 2025 or are uneconomical compared to local wind and solar resources. Add the cost of CCUS—still uneconomical on its own—and the days of coal (clean or not) are numbered.

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