A serious injury of a person recently in a manure-pumping incident in central Iowa has prompted the University of Minnesota to remind pork producers, commercial pumpers and others to watch for a layer of foam on the surface when pumping barn manure pits. This foam contains numerous gases hazardous to people and animals, but methane in particular can cause barn explosions and/or flash fires.
“If a 6-in.-thick or greater layer of foam is present and it is disturbed during normal pit agitation and pumping, a sudden release of dissolved gases will occur,” says Larry Jacobson, an agricultural engineer with University of Minnesota Extension. Without adequate barn ventilation, this can result in methane concentrations reaching the lower explosive level of 5% or 50,000 part per million (ppm). “An explosion is then likely if an ignition source is present from a pilot light, electric spark from a motor or cigarette,” he says.
To guard against pumping accidents, agricultural engineers, animal scientists and pork industry consultants have developed the following recommendations to help producers address this serious safety concern:
Provide continuous ventilation to prevent a gas build-up. Increase ventilation during agitation to quickly dissipate released gases. Sufficient ventilation or exchange of air in the barn is always essential to keep the concentration of methane below its explosive threshold.
- Sufficient air exchange in a barn while agitating and pumping a manure pit is at least two to three times the minimum ventilation rate (or around 10 air changes per hour) for the barn.
- If the pit is full or nearly full, do not rely only on pit fans to supply this airflow rate, since these fans may be severely restricted. It may be better to use only wall fans to supply this air exchange while agitating/pumping the barn’s manure pit since methane gas is lighter than air.
- Make sure your normal ventilation inlets are open and operating properly to ensure good air distribution in the barn. This is also important in preventing animal deaths (if animals must be present in barns) during agitation and pumping of the manure pit.
Turn off heater pilot lights and other non-ventilation electrical systems (such as the feeding system) that might produce an ignition spark. Not providing supplemental heat in the barn may be problematic for cases when there are no animals in the barn or there are only small animals that require warmer inside temperatures. This may restrict when you pump manure from such a barn to warmer days or a warmer part of the day.
When pumping pits that are close to being full, pump without agitation until manure is about 2 ft. below the slats. This will allow pit fans (if available and used) to perform properly during agitation and provide more dilution space for methane and other gases that are released.
According to Jacobson, there is currently no consistent solution to controlling this foaming in pig manure pits. Researchers do not yet understand all the factors (diet, manure pH, others) that cause this problem. Several research projects are ongoing to better understand the causes and eventually provide solutions to this serious problem, he says.
Additional information on this issue can be found at the following Web sites:
- University of Minnesota Extension’s swine Web site: www.extension.umn.edu/swine/porkcast/barnventilation.html 
- Minnesota Pork Board Web site: www.mnpork.com/producers/index.php .
- Manure Pit Foaming. Iowa Manure Certification Workshop. January 2011. www.vimeo.com/22358091 .