EBN's Position on Fly Ash

Fly ash, produced from the combustion of coal in power plants, has recently been a subject of scrutiny by many, including the U.S. Environmental Protection Agency (EPA), which is working on rules for disposal of “coal combustion residuals,” including fly ash. This month’s feature article in EBN (see “Reducing Environmental Impacts of Cement and Concrete,” EBN Sept. 2010) examines the health and environmental concerns of portland cement and fly ash, and we’ve been considering our position on the use of this substance in building materials.

EBN continues to support the use of coal fly ash in building materials as long as

a) the use of fly ash reduces greenhouse gas emissions elsewhere in the materials stream; and

b) the fly ash is chemically or physically locked up so that the risk of leaching is kept acceptably low.

We no longer consider the use of fly ash in products or materials to be an environmental attribute when doing so does not offset greenhouse gas emissions.

Under this policy, we support the use of fly ash in concrete, because it replaces portland cement, which is a highly energy-intensive material to produce and also releases carbon dioxide directly in the calcining process. The concrete effectively locks up any heavy metals, including mercury. However, we no longer embrace the use of fly ash for applications in which it serves only as a filler and does not reduce greenhouse gas emissions. Such uses have included fly ash filler in carpet backing and use of fly ash in soil stabilization.

Further, we call on industry or certification organizations to develop a standard for the content of mercury (and possibly other heavy metals) in fly ash. We envision the development of “hazard concentration grades” for fly ash so that users of that material (whether cement manufacturers, ready-mix concrete companies, or manufacturers using fly ash in other products) can be aware of the level of these toxic constituents and make decisions accordingly.

In our ongoing assessment of the environmental and health attributes of fly ash, we will continue examining and reporting data on leaching of the heavy-metal contaminants in fly ash and will continue to base our position on the best available information. With new products containing fly ash, such as CalStar’s fly-ash bricks (see “CalStar to Begin Production of Fly Ash Bricks,” EBN Jan. 2010), we will be looking for test data showing that leaching of heavy metals is extremely low.

– Alex Wilson