Water from rainfall that drains through the ash in landfills can potentially leach elements in the CCBs. To prevent the dissolved elements from entering the groundwater, most ash ponds are lined with layers of compacted clay and/or synthetic liners. As long as the dissolved elements are confined to the landfill, the risk of mixing with rivers and lakes is minimal. However, the dissolved elements must remain in the landfill forever, unless the water is separately collected and treated. This long term liability can be reduced by increasing the amount of ash that is utilized.
Cement manufacturing is a major contributor of carbon dioxide emissions. For each ton of Portland cement that is manufactured, more than a ton of CO2 is emitted. By incorporating fly ash in concrete, not only is the concrete better and cheaper, but since less cement is required, CO2 emissions are reduced.
Using more CCBs leads to greater environmental sustainability by using less land for landfills and consuming fewer natural resources. Using gypsum produced by scrubbers to make wallboard reduces the amount of natural gypsum that must be mined. Using combustion ash for structural fill reduces the amount of sand and gravel that must be excavated to build roads and buildings. Using fly ash as a raw ingredient to produce cement reduces the amount of clay or shale that must be mined. These are just a few examples of how using CCBs can not only conserve natural resources, but reduce the amount of land used for disposal, making more land available for future generations.