“We are pleased to report that 52 percent of coal combustion products were beneficially used in 2015—up from the previous year’s record of 48 percent. For the first time, we are using more of these valuable resources than we are throwing away,” reports American Coal Ash Association Executive Director Tom Adams, taking stock of the central metric in the group’s latest “Production and Use Survey.”
“With some help from markets and regulatory certainty, we look forward to continuing to grow these practices that conserve natural resources, make products that are more durable, and dramatically reduce the need for landfills,” he adds.
The just-released survey finds that 61.1 million tons of coal combustion products (CCP) were beneficially used in 2015 out of 117.3 million tons generated. Although the ash utilization rate increased from 48 percent to 52 percent, the total volume of material produced and consumed declined. CCP volume declined 10 percent from 2014 levels as coal’s share of the electricity generation mix shrank in response to environmental regulations and competition from other energy sources. Utilization volume declined 2 percent overall in 2015 as usage trends shifted in several key applications:
- Use of coal fly ash in concrete increased 20 percent to 15.7 million tons, up from 13.1 million tons in 2014.
- Use of fly ash and bottom ash in structural fills declined 54 percent and 19 percent, respectively. A 1.9-million ton drop may be related to regulatory uncertainty over an Environmental Protection Agency coal ash disposal rule provision—presently under challenge in court—that requires evaluation of structural fill projects greater than 12,400 tons in volume.
- Utilization of a “non-ash” coal combustion product continued to increase. Synthetic gypsum is a byproduct of flue gas desulphurization units, also known as “scrubbers,” located at coal-fueled power plants. Use of synthetic gypsum in panel products (i.e. wallboard) increased to 12.3 million tons in 2015. Use in agricultural applications, where the material improves soil conditions and prevents harmful runoff of fertilizers, increased to 1.6 million tons.
- Boiler slag production declined 17 percent to 2.2 million tons as more power plants that generate such material were retired. Nearly 84 percent of boiler slag is utilized, mostly as blasting grit or roofing granules.
- Cenospheres, a very valuable form of ash from wet disposal impoundments, saw utilization drop by 80 percent as impoundments began to close in response to EPA’s coal ash disposal rule.
“Although 2015’s results are a milestone worth celebrating, it’s important to remember that the United States is still disposing of millions of tons of coal combustion products that could be put to good use,” observes Adams. “Additionally, the coal ash beneficial use industry is taking significant strides in developing strategies and technologies for reclaiming coal ash materials that were previously disposed.”
He cites a 2015 ACAA-commissioned study by the American Road & Transportation Builders Association confirming ample CCP supplies for beneficial use in the future. “Coal will continue to account for a significant percentage of U.S. electric generation during the next two decades… Even under alternative scenarios of accelerated coal-fueled electric generating unit retirements, CCP production is still expected to exceed overall demand,” study authors conclude.
COAL COMBUSTION PRODUCTS
Generated, Recycled Volumes
SOURCE: ACAA 2015 Production and Use Survey
ASTM MINERAL FILLER STANDARD
ASTM International Committee C09 on Concrete and Concrete Aggregates’ latest standard, C1797, Specification for Ground Calcium Carbonate and Aggregate Mineral Fillers for Use in Hydraulic Cement Concrete, addresses limestone and similar materials exhibiting potential to improve mix characteristics and hardened structure performance.
“Limestone and fillers can help optimize concrete mix designs in terms of workability and finishing by improving packing density,” says C09 member and Euclid Chemical National Technical Service Manager Caroline Talbot. “Notably, this will reduce the amount of cementitious product needed for concrete production, making it a more environmentally friendly alternative.” Testing has also indicated that the presence of ground limestone enhances cement and fly ash hydration, she adds.
C1797-cited materials have been used around the world for years. The standard positions producers and producers to use them without negatively affecting fresh or hardened concrete properties, leading to cost savings and supporting practitioner sustainability measures. The document can be obtained from ASTM Customer Relations, 877/909-ASTM; www.astm.org.