Environmental Benefits of Coal Combustion Products

Environmental Benefits
The use of coal combustion products in construction provides significant short and long term environmental benefits. Specifically, using coal combustion products instead of other materials, such as Portland cement, reduces energy use and greenhouse gas emissions and conserves natural resources. In addition, it prevents the disposal of a valuable resource, reducing the need for landfills and surface impoundments. Finally, the performance benefits of concrete made from coal ash actually leads to additional environmental benefits. Highways and bridges made with coal ash concrete are more durable than those made without it and, therefore, do not need to be repaired and replaced as often.
Greenhouse Gas Emissions and Energy Reductions
Producing cement involves many steps, including grinding and blending raw ingredients (such as limestone, shells or chalk, and shale, clay, sand, or iron ore), heating those ingredients to very high temperatures in a kiln, cooling and mixing those ingredients with gypsum, then grinding down the mixture to form cement powder. This energy-intensive process typically emits nearly one ton of greenhouse gases for each ton of cement created and requires the equivalent of a barrel of oil per ton of cement. Using fly ash, which would otherwise be disposed of, in concrete has the potential to significantly reduce the quantity of greenhouse gases emitted and the amount of fuel used. Typically, between 15 to 30 percent of Portland cement in concrete can be replaced with fly ash. The Federal Highway Administration reports that roads and bridges made with high-performance coal ash concrete can last years longer than those made with Portland cement as the only binding agent. Thus, using coal ash concrete reduces the need to produce new concrete, which consequently means further reductions in future greenhouse gas emissions, energy use, and natural resources.
Resource Conservation
Because fly ash can be used as a replacement for many materials in highway construction, its use reduces the need to quarry or excavate virgin materials such as lime to make concrete, natural gypsum for wallboard and gravel for roofing granules and therefore helps to reduce the environmental impacts associated with these activities. Reducing these operations helps prevent habitat destruction, protect scenic waterways, reduce water runoff and air emissions, and reduce energy use. In addition, each ton of coal ash used beneficially reduces the need for one ton of virgin resources.
Solid Waste Reduction
Although many U.S. industries are using coal combustion products, the United States continues to dispose of more than 80 million tons of this material in landfills and surface impoundments annually. Using fly ash as a substitute for cement in highway construction and other applications could reduce this waste. Typically, a ton of fly ash compacted to 70 pounds per cubic foot takes up approximately 28 cubic feet of landfill space. Every million tons of coal combustion products beneficially used instead of disposed of reduces the need for 656 acre-feet of landfill space. 
Coal Combustion Products Environmental Benefits Quick Facts
One ton of fly ash used as a replacement for cement:

  • Conserves enough landfill space to hold about 1,200 pounds of waste, or the amount of solid waste produced by one American over 270 days.
  • Reduces the equivalent of two months of an automobile’s carbon dioxide emissions.
  • Saves enough energy to provide electricity to an average American home for 19 days.

Coal combustion products can be substituted for many virgin resources that would otherwise have to be quarried or excavated, such as:

  • Limestone and clay to make concrete
  • Gypsum to make wallboard
  • Sand and gravel to make road beds
  • Soil for road embankments