"Clean coal" is a term used by some advocates of coal mining and coal use that refers to the burning of coal as an energy source utilizing technologies to eliminate or greatly reduce harmful emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, mercury, and other substances into the atmosphere. Although various processes have been developed that can reduce the emissions from coal combustion, questions remain about their economic viability and hidden costs, including the costs and environmental effects of disposing of the removed carbon and other harmful substances. According to many critics of the coal industry, the use of the term "clean coal" is an excellent example of greenwashing.*
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* See, for example, Fred Pearce, "Greenwash: Why 'clean coal' is the ultimate climate change oxymoron," The Guardian, February 26, 2009, https://www.theguardian.com /environment/2009/feb/26 /greenwash-clean-coal.