Coal Ash Reclamation

In 2006, our company recycled or beneficially used over 500,000 tons of coal combustion products (CCP). CCP includes ash and slag from the direct combustion of coal.

Cement replacement in ready-mix concrete accounts for over half of CCP reuse, while in construction, aggregate materials and fill material account for the remainder.

The utilization rate declined slightly in 2006 primarily because allowable uses of bottom ash as fill became more restrictive. However, this utilization rate is above the U.S. industry average of 40 percent, as reported by the American Coal Ash Association for years 2004 and 2005.

Coal ash is what's left over after coal is burned in power plants to generate electricity. Alliant Energy's coal-fired generating stations in Iowa burn roughly six million tons of coal annually, producing about 375,000 tons of ash.

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.

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.