There has been considerable coverage surrounding the Dan River coal ash spill and the broader issue of coal ash management. As someone who has worked extensively with coal fly ash (CFA) since I was a graduate student, I want to provide context around its properties, its beneficial reuse and the need for a coal ash management plan.
Coal fly ash is a fine, powdery substance produced from burning coal for generating electricity. Misconceptions about CFA have caught my attention in the wake of recent events. One example: the prevailing narrative that describes CFA as a toxic sludge when in actuality the U.S. Environmental Protection Agency does not designate CFA as a hazardous waste. Toxicity, in fact, depends mostly on concentration and exposure. Check your multi-vitamin’s ingredients. You will likely find boron, chromium, copper, selenium – all of which some people point to as the reason they believe CFA to be hazardous.
CFA can be beneficially reused. Its properties make it a useful construction material and additive for stabilizing soil. The second largest use of CFA is for structural fills or embankments, as is proposed for the Charlotte airport. Other uses include concrete/grout (the number one use), waste stabilization, roofing materials and agricultural applications. In many applications, CFA is placed in direct contact with existing or excavated soils, such as fill material for bridge abutments, retaining walls, roadways and parking lots. If you want high-strength concrete that cures without excessive heat and lasts longer, then you use CFA.
Numerous projects have beneficially reused CFA across the country without any reported problems, including 21 construction projects involving two million or more cubic yards of CFA. The CFA proposed for the Charlotte airport would be enclosed in a state-of-the-art liner system that seals the ash between synthetic barriers, providing a level of environmental protection that exceeds typical requirements for engineered structural fills. Arguably, the extent to which CFA is handled as a solid waste versus a beneficial product is a function of the utilization needs of the construction industry, not the disposal needs of electric utilities. Interestingly, many countries consider coal ash a commercial product. Reuse rates throughout Europe approach 100 percent.
Regardless, like cement or any other construction material, CFA must be managed, regulated and enforced properly to ensure the safety, health and welfare of the public and the environment.
The Dan River incident caused the beginnings of an important conversation: the need for a responsible coal ash management plan. We need a plan that protects against an event like Dan River and determines the level of risk posed by unlined ash ponds to best address those of most concern. Above all, we need a plan that outlines how to reuse and dispose of CFA responsibly.
A robust body of knowledge can inform such a plan. Students and faculty in the UNC Charlotte Energy Production and Infrastructure Center (EPIC) have contributed significantly to the relevant technical literature, case histories and standards that address all facets of CFA management, use and disposal. EPIC stands ready to help with the hard work needed to sort through the issues, inform policy and develop science and engineering-based solutions.
Lastly, such a plan will need a commitment from political leaders and policy makers as well as utility companies. Together, we can find a responsible solution to this national issue.
Daniels is an associate professor in the Department of Civil and Environmental Engineering at UNC Charlotte.
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