Coal refuse

Coal refuse (also described as coal waste, coal tailings, waste material, culm, boney, or gob[1]) is the material left over from coal mining, usually as tailings piles or spoil tips. For every tonne of hard coal generated by mining, 400 kilograms of waste material remains, which includes some lost coal that is partially economically recoverable.[2] Coal refuse is distinct from the byproducts of burning coal, such as fly ash.

Where economically viable, some coal miners try to reprocess these wastes. In more industrialized economies, this may include complex reprossessing,[3] such as fluidized bed combustion in power plants.[4] In less industrialized systems, manual sorting may be employed. For example, in the Jharia coalfield, a large cohort of "coal cycle wallahs" manually sort mine tailings with their families, and then transport the salvaged coal on bicycles more than 60 kilometers to market.[5][6]

Piles of coal refuse can have significant negative environmental consequences, including the leaching of iron, manganese, and aluminum residues into waterways and acid mine drainage.[7] The runoff can create both surface and groundwater contamination.[8] Because most coal refuse harbors toxic components, it is not easily reclaimed by replanting with plants like beach grasses.[4][9]

The burning of waste coal typically produces more environmental toxins than higher energy coals.[1] For every 100 tons of coal waste burned, 85 tons of toxic waste ash are created.[4] These piles are also vulnerable to fires, many of them igniting on their own.[4] There have been some attempts to use coal waste in concrete production, similar to the use of fly ash.[10]

In the United States, most waste coal piles accumulated from 1900 to 1970 when processing techniques were less sophisticated.[11] The US has a longstanding inspection program of these refuse piles.[12] In Pennsylvania alone, there are over 770 such piles identified.[13] There are at least 18 coal waste burning plants in the United States.[14]