Hydrogen Sulfide Release from Dairy Manure Storages Containing Gypsum Bedding.

Recycled gypsum products can provide a cost-effective bedding alternative for dairy producers. Manufacturers report reduced odors, moisture and bacteria in the stall environment when compared to traditional bedding.  Gypsum (CaSO₄·2H₂O) provides a sulfate source that can be converted to hydrogen sulfide (H₂S) under anaerobic manure storage conditions. Agitation of manure storage promotes release of volatile gases including concentrated plumes of H₂S. Incidents have been reported linking injury and death to dangerous levels of H₂S emissions released from manure storages containing gypsum-based bedding.

Observations at farms from three dairy manure categories were compared: (1) typical bedding; (2) gypsum-based bedding, and (3) gypsum-based bedding plus commercial amendment added to storage. Portable meters placed around the perimeter of dairy manure storages recorded H₂S concentrations every minute prior to and during agitation events during fall and spring hauling seasons. Manure samples from just below the surface crust and at the bottom of the storage were collected prior to agitation and a third sample of the mixed manure. A detailed farm characterization documented bedding management, manure handling practices and manure storage inputs.

Results show that manure storage at farms that use gypsum in bedding produced significantly higher H₂S concentrations during agitation than farms using traditional bedding. Manure analyses exhibit increased total sulfur content in manure storages that comprise gypsum in bedding.  A statistical model will be developed to ascertain farm practices or environmental conditions that significantly affect H₂S production and release from storage.  An emissions model will be created utilizing significant parameters to predict dangerous levels of H₂S.