Gypsum Bedding Impact on Hydrogen Sulfide Release from Dairy Manure Storages

Abstract

Abstract. Elevated hydrogen sulfide (H2S) levels have been observed from open-air dairy manure storages that contain gypsum bedding. Gypsum (calcium sulfate), recycled from construction waste and manufacturing defects, provides a cost-effective bedding alternative for dairy cows. Gypsum bedding is reported to control moisture and bacteria in the stalls and can improve soil structure when land-applied. However, gypsum increases H2S production in the anaerobic environment of deep manure storages, which is released in dangerous concentrations when the manure is agitated. This study was undertaken to quantify and compare the H2S concentrations during agitation of manure storages for three dairy stall management categories: farms that use (1) traditional organic bedding, (2) gypsum bedding, and (3) gypsum bedding followed by a treatment added to the manure storage thought to reduce H2S emissions. Three farms used Vital Breakdown (manufactured by Homestead Nutrition, New Holland, Pa.), and one farm used OK-1000 (Pro Ag Solutions, Hawkins, Tex.). Nineteen agitation events at ten farms were monitored during spring and fall hauling seasons. Portable monitoring instruments recorded H2S concentrations around the perimeter of the manure storages prior to and during agitation. Results show that manure storage agitation at farms that use gypsum bedding produced H2S concentrations that were considered immediately dangerous to life and health (above 100 ppm). Increasing gypsum bedding use significantly increased cumulative H2S concentrations (p < 0.0001). Farms that used Vital Breakdown as an amendment significantly reduced cumulative H2S concentrations when compared to farms not using a manure treatment (p < 0.0001). Lower cumulative H2S concentrations at one farm were attributed to the OK-1000 manure treatment. Keywords: Cow, Dairy, Gas, Gypsum, Hydrogen sulfide, Manure, Safety.