Coal Ash Reclamation
In 2007, Alliant Energy utility companies were able to beneficially use over 550,000 tons of coal combustion products (CCP), thereby diverting it from being placed in a landfill as a waste material. This includes fly ash, bottom ash, slag and other by-products generated from the direct combustion of coal.
Over one-half of the CCP use is as a cement replacement in ready-mix concrete with the remainder used in construction/fill applications and as an aggregate in the manufacture of asphalt.
The utilization rate varies from year to year due to variation in local construction activity and changes in approved uses for CCP. The utilization rate for the Alliant Energy utility companies continues to be significantly above the U.S. industry average of approximately 40 percent as reported by the American Coal Ash Association for years 2005 and 2006.
Questions and answers about coal ash
What is coal ash?
Coal ash is what's left over after coal is burned in power plants to generate electricity.
Fly ash is a very fine powder-like particle, ranging in color from tan to black. It's usually collected by electrostatic precipitators that prevent it from being released through the stacks of the plant.
Bottom ash is a brown sand-like material collected in the bottom of the boilers; it's usually ground down and sluiced to holding ponds.
Boiler slag is black, shiny and angular. It is coarser than bottom ash, but is collected and contained in a similar manner.
Coal combustion products are comprised of melted sand and lime with smaller amounts of oxides containing aluminum, iron, magnesium, sulfur and trace materials. These ingredients are the same as the mud and silt that, when combined with organic matter, eventually become coal.
How are coal combustion products used?
Coal combustion products have a variety of construction uses, including road bases, parking lots, alleyways and structural fills, as well as a hardened base for animal feedlots or commodity storage.
Quality-grade fly ash can be used as a replacement for Portland cement in the manufacture of concrete, giving it improved strength, durability and resistance to chemical attack. In addition, it reduces the cost of concrete because fly ash is less expensive than Portland cement.
Fly ash can also be used as structural fill, as a daily cover supplement for landfills, and as an ingredient in flowable fill used to backfill trenches.
Class C fly ash , because of its cement-like properties, can also be used to stabilize loose, plastic soils.
Bottom ash can be used for construction fill, as a replacement for sand in snow and ice control, and as a daily cover supplement for landfills.
Boiler slag can be used for snow and ice control in the manufacture of asphalt and roofing shingles, and as sandblasting grit.
How is Alliant Energy's coal ash recycled?
When we built our world headquarters in Madison, Wisconsin, the concrete used included 244 tons of fly ash. The fly ash is incorporated in the building's footings, walls, columns and the parking garage.
Our headquarters isn't the only prominent building that includes coal ash. Others include:
By using fly ash in our building and encouraging others to do the same, Alliant Energy is proving that fly ash is a sound and economical material in construction applications.
Learn more about coal ash
For more information, contact Jesse Nowak at 319-786-7614 or e-mail jessenowak@alliantenergy.com.
