Disposal and Reuse
Typically 70 to 80 percent of coal ash is disposed of in dry landfills. (Sluiced ashes and sludges are first dewatered in ash ponds then landfilled.) A landfill for a typical coal fired power plant (500-1000 Megawatts) requires about 30 to 60 hectares (74 to 148 acres). These landfills range from about 4 to 80 hectares (10 to 197 acres) and may be as much as 9 m (30 ft) deep.
The remaining coal ash (roughly 20 million MT per year) is used as additives in a variety of applications depending upon the characteristics of the ash. The following list shows the application of the ashes and sludges that were used
Fly Ash, 75% of use is in concrete and cement and in concrete blocks. It is typically substituted for cement in concrete at about 10-30%. It is also used as a filler for asphalt at a rate of about 12%.
Sludge, 57% of use is in wallboard, as roadbase, and other miscellaneous applications, but the total volume used is minimal compared to the total production.
Boiler Slag, 54% of use is as blasting grits and roof granules
Bottom Ash, 30% of use is for snow and ice control and other miscellaneous applications.
Since the early 1970s, all three types of coal ash have been used in construction projects. Coal ash is used to level out uneven terrain or applied as a stable fill for building construction. Typical applications include sites where shopping malls, housing developments, and industrial parks are planned for construction. Other projects have included the construction of road embankments, runways, public transportation system structures, and soil stabilization.
Other emerging applications of fly ash include the construction and sinking of artificial reefs, metal (aluminum and iron) extraction via direct acid leaching, and as a filler in paints and plastics. Examples of products which may contain fly ash include paints and undercoatings, auto bodies and boat hulls, PVC pipes, battery cases, bowling balls, utensils and tool handles, vinyl floor covering, and shower stalls.