The U.S. Department of Energy (DOE) estimates that electric utilities generate about 100 million tons of coal-combustion byproducts. Of this, only about 30 million tons are recycled. These byproducts include:
53%: Fly ash — A talcum-like solid in the flue gas from a coal-fired boiler
25%: Sludge from wet flue-gas scrubbers
16%: Boiler ash — Heavier, coarser solid found at the bottom of the boiler
7%: Boiler Slag—A hard, glassy material made by boiler ash melted by the heat of the combustor
The DOE wants to increase coal byproduct use from 30% to 50% by 2010. It believes the economic benefit of these byproducts could bring $500 million-$1 billion to the economy.
