Earthworms and Type-X Drywall
The benefits of gypsum (CaSO4 · 2H2O) as a soil amendment are well established: gypsum improves soil tilth, particularly in clayey soils, and effectively displaces the sodium in soils that have high salt content. Research has shown that applying ground-up scrap gypsum board gives the same benefits as agricultural-grade gypsum at rates of up to 22 tons per acre (49 tonnes/ha). Procedures for land application of gypsum-board scrap are documented in the NAHB Research Center’s Residential Construction Waste Management: A Builder’s Field Guide (see review in EBN ) and on the Gypsum Association’s Web site, .
But two large commercial construction projects have raised a new concern: what about land application of Type-X drywall? Type-X board is thicker (5/8” instead of 1/2”), denser (about 2.2 vs. 1.6 lbs/ft2, or 10.7 vs. 7.8 kg/m2), and contains a small amount of glass fiber (less than 1% textile grade by weight in Type-X). Both the new Alliant Energy facility in Madison, Wisconsin and the Stone Crest Shopping Center in Atlanta, Georgia have generated up to 80 tons (73 tonnes) of scrap Type-X drywall, and the general contractors—Opus North in Madison and Winter Group in Atlanta—have construction waste management plans that call for land application of scrap gypsum board as a soil amendment. But none of the research supporting gypsum board as a soil amendment has included Type-X. Jenna Kunde of WasteCap Wisconsin was in a bind. She wanted to support the innovative recycling program of Opus North, but she also wanted to ensure that the glass fibers would not be a problem in land application. After broadcasting this question widely on the Web, Kunde heard from Jim McNelly of the U.S. Composting Council—why not use the ASTM “earthworm contact test?” Developed in 1984 by researchers at Cornell University and recognized by the U.S. Department of Agriculture, ASTM E1676-97 uses earthworms for a laboratory soil toxicity or bioaccumulation test. The number, weight gain, and reproductive activity of the earthworms are used to assess the impact of the soil additive on the biological community. Following this suggestion, Dick Wolkowski, a UW–Madison soil scientist, applied the earthworm test to soil samples ranging from no Type-X gypsum amendment (his control) to the equivalent of 8 tons per acre (18 tonnes/ha). The results? “There was no impact at any of the gypsum application rates—in weight, number and condition; all the earthworms fared equally well over the six weeks,” said Wolkowski. In Wisconsin, land application of the Type-X drywall is taking place on nearby farmland, and in Georgia it has been used as a site landscaping amendment. The waste management implications of this issue are significant. Total annual U.S. production of Type-X wall board in 2000 was 8.88 billion ft2 (825 million m2), or 31% of total board production in the U.S. Since cutoff waste typically represents about 10–15% of the material, this represents about one million tons (970,000 tonnes) of gypsum material that could be land-applied.
For more information:
2647 N. Stowell Avenue
Milwaukee, WI 53211-4299
414/961-1100, 414/961-1105 (fax)
Stephanie Busch, Program Manager
DOD Solid Waste, C&D, Commercial/Institutional Programs
P2AD, Suite 450
7 Martin Luther King, Jr. Drive
Atlanta, GA 30334
404/651-5120, 404/651-5130 (fax)