Waste-to-energy facilities burn trash to generate electricity. After combustion, an ash residue remains that traditionally has been disposed in landfills. But, disposal isn’t the only option. Nearly 3 million tons of ash, or more than one-third of all residues, are being reused annually as landfill roadbed material, daily and final landfill cover, road aggregate, asphalt-mixture, and even in the construction of artificial reefs and cement blocks.

In accordance with the federal law, waste-to-energy ash is tested to ensure it is non-hazardous. The U.S. EPA developed a test called the Toxicity Characteristic Leaching Procedure (TCLP) that subjects ash to acidic liquid, causing metals to leach from the material. If metals leach in amounts greater than a fraction of a percent, the ash is considered hazardous. Years of testing ash from every waste-to-energy facility in the country has proven that ash is safe for disposal and reuse. Waste-to-energy ash consistently passes TCLP, despite the fact that the TCLP test greatly exaggerates the potential for metals to leach from ash into the environment.

Test results and measurements taken in the field show that the levels of metals present in waste-to-energy ash leachate are close to the significantly more restrictive drinking water standards and far lower than the TCLP toxicity criteria.

Waste-to-energy ash represents about 10% of the volume of the trash combusted. Ferrous metals are removed from the ash at the facility, leaving a residue that looks a lot like wet cement. Waste-to-energy residue actually has physical properties similar to construction mixtures such as concrete. After a short time, waste-to-energy ash “cures” and resembles concrete.

Exciting research on waste-to-energy ash is underway by the University Ash Consortium established by the Columbia University Earth Engineering Center and the Waste-to-Energy Research and Technology Council (WTERT). For more information, please visit the WTERT website.

Resources:
Ash Reuse Fact Sheet