Coal pollution mitigation emissions of sulfur dioxide or oxides of nitrogen associated with the utilization of coal in the generation of electricity." Before being adopted in this fashion, historically "clean coal" was used to refer to clean-burning coal with low levels of impurities, though this term faded after rates of domestic coal usage dropped. The term appeared in a speech to mine workers in 1918, in context indicating coal that was "free of dirt and impurities." In the early 20th century, prior to World War II, clean coal (also called "smokeless coal") generally referred to anthracite and high-grade bituminous coal, used for cooking
Coal breaker floor and slid down a gently inclined "picker table" where breaker boys removed obvious impurities such as rocks and large pieces of slate and threw them down chutes to the culm pile. The breakers also removed obviously clean lumps of coal and sent them down a separate "clean coal" chute for crushing. Lumps intermixed with impurities would go down a third chute for crushing and further cleaning. On the second level of a typical breaker, coal would be roughly sorted. The fuel would move over sorting bars, with the various sizes of coal going down different chutes. Each type of