Last fall’s weather-related delays in corn and soybean harvests produced major delays in manure pump-out and land application, setting in motion potentially dangerous situations on some hog operations.

“Unfortunately, several Midwestern swine facilities suffered flash fires and explosions related to liquid manure agitation and pumping from deep pit concrete storage,” says Allan Stokes, director of environmental programs for the National Pork Board.

Due to the rash of reported incidents, the Pork Checkoff’s Environmental Committee contracted with Iowa State University (ISU) researchers to conduct a literature review of the science related to the causes and possible factors and sources for manure-related explosions and flash fires.

The ISU researchers found:

  • Explosions and fires related to deep-pit manure storage have been experienced as early as 1969.
  • Gases resulting from anaerobic decomposition of manure (methane, hydrogen sulfide and phosphine) are the suspected source of most fires.
  • Methane is the most likely source of barn fires, since the lower explosive limits for both hydrogen sulfide and phosphines are far above the toxic level for swine and humans. Animal death would likely occur before either gas reached combustible levels.
  • Foaming may occur in anaerobic manure systems. This action increases the potential hazard as methane is trapped in the foam and released during manure agitation.

The full literature review and the Pork Checkoff’s Safe Manure Removal Policies Fact Sheet can be found on the Pork Science page on the checkoff’s Web page at

For more information, contact Allan Stokes at or (515) 223-3447.