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Control for swine manure deep-pit foaming

September 11, 2013  by Chuck Clanton and Larry Jacobson University of Minnesota

An example of manure foaming at a manure pit access port. Iowa State University

For swine farmers in the upper Midwest, fall brings heightened safety concerns as the manure deep pits fill under their barns.

Since 2009, at least 20 Minnesota swine barns have experienced flash fires or barn explosions as a result of manure deep-pit foaming. About 25 percent of finishing barns in the upper Midwest have identified foam in their manure pits, and thus the potential for explosions or flash fires, according to a producer survey conducted by the University of Minnesota Bioproducts and Biosystems Engineering Department.

Human and animal safety is paramount, as is protecting buildings and their contents. To prevent fires and explosions, producers should follow several recommendations. Most importantly, producers should monitor regularly and determine the depth of foam, if any, in their manure pits. This should happen at least weekly.

Action is needed if foam depth is above six inches and within 24 inches of the underside of the slatted floor. Action could include one or both of the following:

  • Use a pit additive such as Rumensin to reduce foam depth.
  • Remove some of the manure to allow additional capacity and headspace above the surface.

Be sure to use the proper level of barn ventilation, based on outside temperatures along with animal age and size, to maintain acceptable air quality and keep methane concentrations below the explosive level. The barn’s ventilation system should never be turned off, even if there are no pigs in the building. For the unoccupied building, the minimum ventilation rate used for finishing pigs should be used to prevent methane buildup. The constant running of minimum ventilation rate should be five to 10 cubic feet per minute (CFM) per pig space (varies with age and size of pigs). Review references or handbooks with detailed information on ventilation management in swine facilities based on animal age and size (MWPS-32 Mechanical Ventilation Systems for Livestock Housing, 1990 or MWPS-33 Natural Ventilation Systems for Livestock Housing, 1989).

  • Emergency backup electrical generation is needed in case of main power failure.
  • Eliminate any source of sparking or flames, including:
  • Cigarettes, cigars, pipes, etc.
  • Sparking switches or motors.
  • Sparking or pilot light on water and/or space heaters.
  • Welding and/or grinding during repair of gates, feeders, waterers, and the like.
  • Additional recommendations include:

For adequate pit fan ventilation airflow, maintain a minimum of 12 inches of space between the top of the manure or foam and lowest concrete beam.

Remove pigs from barn, if possible, when agitating and/or pumping manure. If not, use the maximum ventilation rate (roughly 10 times greater than the minimum rate) for an all mechanically ventilated system. For naturally ventilated buildings, curtains should be fully open with a breeze (minimum of 10 mph). People should never enter a building during manure pit pumping.

No liquid should leave the manure pit surface (rooster tailing) during agitation.

To learn more about manure management and air quality from University of Minnesota Extension, visit

Chuck Clanton is a professor in the College of Food, Agricultural and Natural Resource Sciences. Larry Jacobson is an engineer with University of Minnesota Extension.


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