Gypsum Spikes Dairy Manure Gas Risks Even Outside Pits

Gypsum, often mixed with dairy manure, spikes manure gas risks even outside pits during agitation and pumping.

Published on: Oct 21, 2013

Last year, three Northeast farm youths were nearly overcome by dairy manure pit gases as they walked by a pit being agitated. Now, there may be a clue to why.

Recently, the Benton, N.Y., fire department and Yates Soil and Water Conservation District measured more than 100 parts per million of  hydrogen sulfide next to a long-term dairy manure storage pit during agitation – next to, not in the pit. It occurred on a farm where gypsum has been used for bedding.

That highly dangerous level prompted Cornell Pro-Dairy experts to issue a "heads up" warning last week to farmers and manure handlers. Under certain conditions, hydrogen sulfide can be a problem in any long-term storage. But the level found there was far higher than measured in other locations.

HIGH-RISK AREA: Long-term manure storage areas are hazardous enough to be fenced, signed and equipped with safety equipment, especially during agitation and pumping.
HIGH-RISK AREA: Long-term manure storage areas are hazardous enough to be fenced, signed and equipped with safety equipment, especially during agitation and pumping.

Air was also tested around the manure storage perimeter of a different Yates County farm that didn't use gypsum for bedding. H2S levels were overall undetectable.

Manure from barns where gypsum is used for cow bedding may be at increased risk to release hydrogen sulfide gas high enough to be hazardous, even be life threatening. Since fall is prime manure spreading time, the dairy experts issued this "heads up" alert.

Why gypsum is a concern 

Gypsum is a significant source of calcium and sulfur. Naturally occurring bacteria in liquid manure storages uses that sulfur to make hydrogen sulfide. The health risk is high enough that gypsum cannot currently be used as bedding on farms with long-term manure storage in the United Kingdom.

Hydrogen sulfide levels above 20 ppm can begin to cause human problems, including headaches, dizziness and fatigue.  According to the Occupational Safety and Health Administration, concentrations of 100 ppm hydrogen sulfide are immediately dangerous because the symptoms can make it hard to escape from the situation. 

Levels above 100 ppm paralyze your sense of smell, so you aren't aware you're breathing in the gas. Above 500 ppm, staggering and collapse can occur in five minutes, death after 30 to 60 minutes.

The point: If random air samples test more than 100 ppm, it's possible to have pockets of hydrogen sulfide near storage structures during agitation that are much higher. All workers, visitors and family members should exercise extreme caution, particularly where gypsum has been used.

The Cornell experts acknowledge that operations that daily-haul manure and use gypsum for bedding, there's little or no production of hydrogen sulfide.

Consider these manure-storage precautions

If you have stored manure with gypsum material and are planning to agitate and land apply manure, the following precautions should be taken:

  • Make sure no unnecessary people are near the pit or open air storage during agitation and pump out.
  • Set up large fans and/or blowers around where operators will be working to mix air and dilute any gases.
  • Pit operators should be trained to use respirators and how to work in hazardous places. 
  • Use a respirator when working around the pit during agitation and filling. 
  • If entry is necessary, never do so during agitation.  Enter only if the pit is well ventilated, fresh air is supplied to a respirator and a safety harness and attached rope is worn and there are two people standing by to help.
  • Train all family members and employees on the dangers of manure gases.
  • Install gating/fencing and danger signs around all manure storages.

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