Last year there were several documented cases of manure pit fires and explosions in Iowa. Not all of these incidents happened during agitation and pumping, nor did all of the pits have foam present when the fires or explosions happened.
Iowa State University Extension program specialist Angela Rieck-Hinz and Extension agricultural engineer Shawn Shouse say these episodes highlight the caution needed when agitating and pumping manure from pits beneath buildings.
Liquid manure in pits undergoes slow decomposition which creates several gases including methane and hydrogen sulfide, both of which can create dangerous situations. The rate of gas release from the manure can be drastically increased when the manure is agitated (stirred) during pumping. This increase is especially true for hydrogen sulfide, which can have a lethal paralyzing effect.
In addition to the concern about gas release from pumping and agitation is the concern about rapid gas release in pits with excessive foam. It is believed that pits with substantial foam prevent the normal release of methane from the deep-pit facilities. Captured methane can be released quickly when the foam is disturbed by agitation or other activities such as power washing. The rapid release of methane mixing with fresh air can create an explosive mixture. If this mixture comes into contact with an ignition source, it can cause a flash fire or explosion.
To minimize risk of injuries and flash fires, manure handlers should follow these steps:
Never enter a building or manure storage structure when liquid manure is being agitated or pumped. A video discussing safety practices for pumping from deep pits can be found at: http://vimeo.com/15463270.
Manure gases are an unavoidable byproduct of liquid manure storage. Strict safety protocols along with proper ventilation and agitation practices can minimize the risk of flash fires and explosions during manure pumping, the specialists emphasize.