Researchers are at a loss for what might be causing hog manure to suddenly become explosive. Six hog farms have exploded since 2009. University of Minnesota's Agricultural Engineer Charles Clanton says, "This has all started in the last four or five years here. We don't have any idea where it came from or how it got started. Whatever has happened is new." The farms have blown up because a spark has somehow ignited methane that has become trapped in some sort of unidentified form of foam that has been developing in manure pits.
These hog manure pits have always been emptied regularly. Believe it or not, the waste generally builds up and acts just like a giant stomach. These waste pits become caldrons in which single-celled organisms and bacteria metabolize the muck, which creates the methane. Big fans are typically used to keep the methane from reach any explosive levels. The new foam that is being found is trapping the methane in its bubbles. Amazingly, this foam can reach a depth of four feet or more.
When these bubbles are disturbed, large amounts of methane are released in a very short period of time. All it takes it a little spark and the barn where these pits are housed becomes a bomb and can explode. Researchers are stumped as far as what is causing the foam to be created. There are several theories. It could be caused from new bacterial communities or an actual change to the molecular structure of hog manure caused by new kinds of feed. There has been a dramatic rise in the United States in the use of distiller's grain in hog food and there is evidence that shows it may be linked to this foam.
There is also the possibility that it may come from soaps used to clean the pits. Scientists have observed that it is seemingly random in regard to which farms have it and which do not. Also, once the foam is formed it keeps coming back. The foam seems to be located in a limited area so far that includes Northern Iowa, Southern Minnesota, Illinois and Wisconsin. Angela Kent, a University of Illinois Microbial Ecologist says, "I don't think it's a dangerous new microbe. I think it's a shift in the environment that's favoring a particular microbial assemblage that's inadvertently causing this."
In September of 2011, a spark caused from a typical metal repair on a farm caused an accidental explosion on an Iowa hog farm that injured a farm worker and killed 1,500 hogs.