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
Carbon, Iowa originally named Walters, after its first settler, but was renamed Carbon after the discovery of coal. The town was established in 1873, but was not incorporated until 1903. A post office was established in Carbon in 1874, but from 1877 to 1880, the name was changed to Shinn. By the time of the Civil War, there were small coal mines along the riverbanks near Carbon. In 1894, there were 9 coal mines in Carbon, of which 5 were in current use. Typical mine shafts were 80 feet deep, working a coal seam 12 to 20 inches (30 to 50 cm)