Fly Ash Basics and Beneficial Reuse

What is fly ash?

When coal is burned to make electricity in power plants coal ash is produced. This coal ash creates a heavy ash, called bottom ash, that falls to the bottom of the boiler. As the remaining ash floats with the flue gases, a filter captures the finer particles so that nothing is released into the atmosphere. Those finer particles are what we call fly ash. About 43% of all fly ash in the U.S. is recycled, the remainder goes into landfills.

Fly Ash Reuse

According to the American Coal Ash Association, the primary uses of coal ash include:

  • Concrete production, as a substitute material for Portland cement and sand
  • Embankments and other structural fills (usually for road construction)
  • Grout and flowable fill production
  • Waste stabilization and solidification
  • Miscellaneous other uses

Recently, Class C fly ash has been proven to be an effective component in the making of masonry products. When mixed with water, it becomes self-cementing and does not require an activator. It is also said to harden and get stronger over time.

Is fly ash safe to use – Expert Quotes

“For some types of Coal Combustion Waste (CCW), there are alternative uses as raw material for construction products such as concrete, plaster, and wallboard. When directed toward these ‘encapsulated uses,’ the dangerous chemicals in the waste are not subject to erosion and leaching into the environment, but unfortunately the majority of CCW is not disposed of in this way.”“Dangerous Disposals: Keeping Coal Combustion Waste Out of Our Water Supply” issued as NRDC “Health Facts”
“Reuse of ash as a component of asphalt, concrete, and gypsum board are legitimate and safe reuses that should be encouraged. In addition, recycling ash in concrete can result in a large reduction of greenhouse gases …”Testimony of Lisa Evans, Earthjustice, before the U.S. House Subcommittee on Energy and Mineral Resources, June 10, 2008