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
Metallurgical coal Metallurgical coal Metallurgical coal is a grade of low-ash, low-sulfur and low-phosphorus coal that can be used to produce high grade coke. Coke is an essential fuel and reactant in the blast furnace process for primary steelmaking. The demand for metallurgical coal is highly coupled to the demand for steel. Primary steelmaking companies will often have a division that produces coal for coking, to ensure stable and low-cost supply. Metallurgical coal is distinguished by the strong low-density coke produced when the coal is heated in a low-oxygen environment to reduce mineral impurities (e.g. less sulfur, phosphorus). On heating, the coal