Accumulation of hydrogen sulfide in dairy manure in relation to gypsum use and possible solutions

Open Access
Brown, Vance David
Area of Honors:
Animal Sciences
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Eileen Eilzabeth Fabian, Thesis Supervisor
  • Troy Ott, Honors Advisor
  • hydrogen sulfide
  • gypsum
  • dairy manure
  • iron oxide
Hydrogen sulfide is a deadly gas that has recently become an issue on dairy farms across the country. Upon agitation of manure storages, large quantities of hydrogen sulfide have been released into the air and caused morbidity and mortality to farmers and their animals. Anecdotal evidence reveals that the use of recycled gypsum in the dairy barn as a bedding amendment appears to be the cause of this elevated hydrogen sulfide accumulation in manure storage systems. Recycled gypsum, or CaSO4, contains sulfate. Certain bacteria have the ability to reduce sulfate in an anaerobic environment and acquire energy. Given a long enough storage time, limited disturbance, and the formation of a surface layer crust, an anaerobic environment is created below the surface of a large storage pit. When the environment becomes anoxic enough, sulfate-reducing bacteria convert the sulfate into hydrogen sulfide gas. This gas can then build up in the manure and remain trapped until agitation. This study investigated the relationship between gypsum presence in the manure and hydrogen sulfide accumulation in a laboratory setting. It was determined that gypsum presence did, in fact, cause significant hydrogen sulfide accumulation. Secondly, solutions to mitigate this risk were tested. The first solution was Vital Breakdown™ (Homestead Nutrition, New Holland, PA), a proprietary product manufactured by Homestead Nutrition, Inc. designed to accelerate microbial decomposition and reduce odors from manure storages. The second product contains iron oxide, a recycled material that has the potential to bind to hydrogen sulfide and render it insoluble. Both solutions had a promising effect on reducing blooms of hydrogen sulfide emissions in this study. Iron oxide appeared to reduce hydrogen sulfide dramatically when used at a specific inclusion rate. Vital Breakdown™ promoted the slow release of hydrogen sulfide from the manure rather than accumulation. Large scale investigations on dairy farms are the next step to determining the effectiveness and practicality of the proposed solutions.