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USDA-NRCS Drywall Recycling Grant

Background

Michelle Fisher and Bruce Galbreath of Drywall Recycling of Montana (DRM) identified a need for drywall recycling in the Missoula area after they observed that drywall scrap accounts for over a quarter of residential construction waste. They knew of several successful drywall recycling programs in other parts of the U.S. and Canada that turned the scrap into new drywall or reprocessed it into an agricultural soil amendment.

In 2005, DRM was awarded a Conservation Innovation Grant from USDA-Natural Resources Conservation Service to "develop, test, and promote use of recycled drywall gypsum as an effective natural soil amendment, and demonstrate a model local recycling and use program."

The project participants are voluntary Montana farmers and ranchers that promote agricultural production and environmental quality as compatible national goals through the government-funded EQIP (Environmental Quality Incentives Program), which offers financial and technical assistance to eligible participants for the installation or implementation of structural and management practices on eligible agricultural land.

Project Progress

DRM conducted two seasons of field studies to determine the effects of recycled gypsum drywall applications to EQIP fields in Central and Western Montana in 2006 and 2007. The focus was particularly on sodic and saline soils, which may be ameliorated by additions of gypsum to displace the sodium from clay particles and generate soil aggregation and aggregate stability.

Scrap gypsum drywall was pulverized and screened to create fine pieces devoid of paper. This product was applied to experimental plots in the Spring, soil samples were collected in the Summer, and biomass was harvested in late Summer or Fall.

2006 Studies - Download full report (Adobe PDF - 91 KB)

The first season evaluated the effect of three concentrations of the recycled drywall product on alfalfa, potato, and barley. Results showed no significant effects of gypsum application on the variables tested (EC, pH, PMN, Ca2+, Mg2+, K+, Na+, %WSA, and biomass). While some of this lack of response may be due to difficulties coordinating with producers (i.e. farmer harvesting prior to biomass sampling, or the high level of cultivation activity associated with potato farming) obscuring treatment differences, it is likely that the relatively unweathered soils of Western Montana contain sufficient calcium and sulfur such that gypsum application results in no increase in plant biomass or favorable soil properties (%WSA, PMN, NH4+).

2007 Studies - Download full report (Adobe PDF - 138 KB)

The second season focused on gypsum application to saline and saline/sodic suspected soils since gypsum application is an accepted method of ameliorating saline seeps. The three sites consisted of a dryland range site under sparse wild rye, an irrigated hayfield under alfalfa and pasture grasses potentially slightly contaminated by the collapse of tailing holding ponds near Opportunity, and a sodic soil which had recently been put under irrigation. Gypsum application significantly increased exchangeable Ca2+ levels from Control and Low treatments to Medium and High treatments at all three sites. Significant increases in electrical conductivity (EC) were observed at two sites, confirming dissolution of gypsum treatments in those soils. Biomass and % water stable aggregates (%WSA) were non-significant at all sites; however, gradients present in the field may have obscured treatment effects at one site.  Results from 2007 field experiments indicate that gypsum applications can increase exchangeable Ca2+ levels in one growing season; however, more time is likely necessary for the increased Ca2+ to positively impact %WSA, biomass and exchangeable sodium percentage (ESP). Gypsum application to Montana saline-sodic soils may increase soil productivity in the long term; however, more research will be necessary to determine frequency of applications necessary to attain a desired level of soil quality improvement.

2008 Studies in Progress

The third season of research will be conducted in the Bozeman, Montana area, due to positive feedback on our product from our EQIP producers in that region. Studies will be continued at 2007 field sites for another two years. Please see our recommendations for recycled gypsum field application that we have developed as a result of the past two years of study. Download Guidelines for the Application of Recycled Gypsum as a Soil Amendment in Western and Central Montana Agricultural Soils (Adobe PDF - 22KB).