Jury Still Out on Manure Gas From Gypsum Bedding

7/13/2013 7:00 AM

The Livestock and Poultry Environmental Learning Center held a national conference in Denver, Colo., the first week in April. The title was From Waste to Worth: “Spreading” Science and Solutions.

The focus was to integrate research, education and Extension efforts related to managing environmental impacts of livestock and poultry production.

Penn State Extension was well-represented. Rebecca White and I conducted our certified feed management workshop; I presented a paper on sustainable dairy cropping systems; and Robb Meinen presented on gypsum bedding — risks and recommendations for manure handling.

There was a diverse audience attending this conference, ranging from government agencies, universities, consultants, veterinarians and probably others.

People came from across the country as well as from outside the U.S. At lunch one day, I was talking to a veterinarian who had sat through Robb Meinen’s presentation on gypsum bedding.

Recently, several incidents involving human and livestock death or injury have highlighted the possible creation of dangerous gases at farms using gypsum bedding.

This was completely new to her and she was glad she listened to his talk as it made her more aware of problems that until recently were fairly uncommon.

Robb is a senior Extension associate who oversees the manure haulers’ program in Pennsylvania. He worked with several specialists from Penn State and the University of Wisconsin on the mechanism of how and when this gas is developing.

Gypsum bedding has provided an alternative to dairy producers, especially with the limited availability of common bedding sources and their high prices.

Gypsum products, recycled from construction industry waste streams, provide low input-cost bedding. Some dairies report decreased somatic cell counts. However, the price is too high if it is the cause of fatalities on farms.

Human lives have been lost at two separate events. In a third incident, 2- and 4-year old brothers were found unconscious adjacent to a manure storage but experienced a complete recovery.

In all of these places, gypsum was used as bedding. Is this coincidence or does gypsum play a role in production of dangerous gases?

There is much to learn on this matter, yet this can serve as a reminder that all manure storages can produce gases and precautions should be exercised, especially when manure is being agitated, moved or pumped.

In the European Union, several agencies have discontinued the use of gypsum as bedding based on losses of livestock as well as previous policies that restricted gypsum from landfill disposal.

Gypsum is a common term for hydrated calcium sulfate (CaSO4-2H2O). It is suspected that under the right manure storage conditions anaerobic bacteria convert the sulfur (S) in gypsum to hydrogen sulfide (H2S), a gas that can be deadly.

Movement such as agitation of manure can lead to large H2S fluxes and localized dangerous levels of the gas.

While this is concerning, there remain many farms that use gypsum without incident. Data on this subject are lacking.

The purpose of presenting this topic at the Waste to Worth Conference was to increase national awareness of several deaths and severe injuries that have occurred recently in the Mid-Atlantic area involving manure gases.

Several dairies where incidents occurred use gypsum. There is concern that gypsum increases dangerous hydrogen sulfide emissions from manure storages at these farms.

In a true first step to determine gas productions associated with gypsum in manure, preliminary bench-top scaled comparisons of manures with and without gypsum are ongoing in Pennsylvania and Wisconsin.

At this time, there is no clear-cut understanding about what is occurring. Literature and base knowledge on this subject are lacking. More work is needed to assess the actual risk to workers around manure storages where gypsum is present.

There are countless factors that can contribute to gas production from manure storages. Identification is needed of key factors that may lead to production of hydrogen sulfide when gypsum is present.

Further outreach to manure handling industries is warranted.

Virginia “Ginny” Ishler is a nutrient management specialist and manager of Penn State University’s dairy complex.

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