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 more marketable product. Here, a series of interlocking, toothed crushers or rollers would break lump coal into progressively smaller sizes. On the fourth level down, the coal was further cleaned of impurities. This was originally done primarily by hand, but hand picking was gradually supplanted after 1910 by improved screens and jigs. Although breaker boys worked at all levels of the coal breaker, most of the removal of impurities by hand occurred on this level. (Some picking did occur on the ground level of the coal breaker, where boys would locate good pieces of coal in the culm and return