For decades fly ash has proven to be a valuable additive for concrete buildings, Poduri, și alte structuri. Cu toate acestea, as coal-fueled power plants are phased out, a steady supply source is diminishing. Because of declining coal power generation, rising demand as a cement extender in concrete, and environmental concerns for fly ash stored in landfills and ash ponds, harvesting and beneficiating fly ash residing in impoundments is gaining momentum. With over a billion tons stored in impoundments, there is enough fly ash to meet demand for decades.