Coal breaker remaining. The sorting by size is particularly important for anthracite coal. In order to burn efficiently, air must flow evenly around anthracite. Subsequently, most anthracite coal is sold in uniform sizes. In the 1910s, there were six commercial sizes of coal (with the smallest size having three subsets): Coal pieces smaller than in size were considered "culm," and unable to be separated from the impurities (and thus useless). The grade of coal ranged from a low of 5 percent impurities for steam or broken coal to a high of 15 percent for pea-size coal and its subsets. Coal breakers were
Coal power in the United States facilities hold the noncombustible ingredients of coal and the ash trapped by equipment designed to reduce air pollution. Byproducts of coal plants have been linked to acid rain. 86 coal powered plants have a capacity of 107.1 GW, or 9.9% of total U.S. electric capacity, they emitted 5,389,592 tons of SO in 2006 – which represents 28.6% of U.S. SO emissions from all sources. Emissions from electricity generation account for the largest share of U.S. greenhouse gases, 38.9% of U.S. production of carbon dioxide in 2006 (with transportation emissions close behind, at 31%). Although coal power only accounted for 49%