Gypsum Bedding and Deadly Hydrogen Sulfide Gas

In the wake of two preschool boys who were knocked unconscious while nearby their family's dairy manure storage, a partnership between Penn State Extension, two companies, and the Natural Resources Conservation Service was formed to not only sort out the cause of this accident during manure agitation but also resolve to prevent further incidents. Both goals were accomplished.

Within the previous year, fatalities on separate dairy farms during manure agitation were also suspicious as all of these manure storages were open-air, uncovered facilities that would seem to present limited danger for manure gas exposure compared to closed, covered, or confined manure storages. In each case a link to gypsum bedding use, gypsum chemically being calcium sulfate, in the dairy cow barn seemed to offer a clue. Through demonstration trials at ten dairy farms during 2014-15 it was determined that dangerous levels of hydrogen sulfide [H₂S] gas during manure agitation was very likely the culprit contributing to the two boys being knocked unconscious and the other farm fatalities. Dairy farmers realize that dangerous manure gas will be emitted during manure agitation. Yet prior to this Extension demonstration project there seemed to be limited realization that such high levels of hydrogen sulfide gas trapped within the manure slurry would be released in a burst if the dairy manure contained significant amounts of sulfur compounds, whether that be from gypsum bedding, poor water quality, or other sources.

One of the more effective aspects of this project was the partnership between academic, business, and government interests. A gypsum bedding supplier, USA Gypsum, and gas monitoring instrumentation supplier, Industrial Scientific, were close collaborators and partial sponsors of the project. Inclusion of expertise of these two business' personnel and, of course, the ten dairy farm collaborators meant real-world aspects of manure agitation events were documented and understood. Dissemination of project findings and solutions was facilitated by these businesses and NRCS having close everyday ties to the dairy industry.

During the timeframe of the NRCS-Conservation Innovation Grant funded project there were numerous field days, Penn State news releases, conference presentations on local and national scale, fact sheets, and peer-reviewed journal articles outlining the findings that liquid manure containing gypsum could release extremely high levels of deadly hydrogen sulfide gas. The ag popular press was involved with dozens of articles, some to the point, "Manure handling field day focuses on hydrogen sulfide gas," and others more attention getting: "Dangerous manure moves to a higher level" and "It's coming! Don't let it get you!" Two of the Penn State agricultural engineering department's Extension teams, Safety and Air Quality, worked together to develop and present the many outreach products.

Mid-term Impact. National events for professional manure haulers featured not only the potential dangers during agitation, for any type of manure, but also increased awareness and use of instrumentation to test conditions. Further trials were conducted at lab scale to find additives or mixtures of gypsum bedding that offer its beneficial features while lessening the hydrogen sulfide release. Promising results are available, albeit at higher product cost. The current recommendation is to encourage responsible use at lower gypsum levels in a mixture with conventional bedding. With close NRCS involvement, the findings have been officially included in their National Bulletins and Fact Sheets. This has resulted in widespread awareness for design of manure storages, operation during agitation, and increased caution and restrictions when the liquid manure storage contains sulfur, such as gypsum.

Long-term Impact: Circling back to the seminal event that ignited the search for an answer to farm fatalities during outdoor manure storage agitation, the father of the two unconscious boys was able to successfully move the boys away from the storage and to the hospital. He and others are now aware of the heightened dangers during manure agitation, particularly with higher levels of sulfur in the manure. The farm continues to use gypsum bedding without further incident with increased respect of the inherent and unpredictable dangers during agitation of any liquid manure. In recent conversation with the owner of USA Gypsum, it is comforting to realize that even with his gypsum bedding sales steady, if not increasing slightly, we know of no further fatalities during gypsum-manure agitation*. Although it is impossible to prove that the lack of incidents is tied to our project outreach of findings, it is clear that there is increased awareness of the potential dangers of sulfur in manure. Most of that information came initially from our Penn State Extension demonstration project, which has been shared nationally. For new customers thinking about adopting gypsum bedding for the many benefits, the company president says they ask about the downside of dangerous hydrogen sulfide release at manure agitation. Information about the benefits and potential gas release are available at this gypsum supplier website, various Extension websites, and within NRCS as operating recommendations and bulletins. A side benefit of the focus on gypsum-laden manure has been an increase in awareness of the caution needed for life-threatening gas risk during manure agitation whether in a confined space or outdoors.

* Penn State Extension, Ag Safety program's 2015-2019 Pennsylvania Farm Fatalities Summary indicates no manure gas incidents from any farm management system.