A sample of the manure foam that caused an explosion that lifted a hog barn two feet off the ground and blew a man 20 feet away from where he had been standing.
When you hear about foam in the context of food, you might think of the culinary innovations of the Spanish chef Ferran Adrià, who’s famous for dishes like apple caviar with banana foam.
But this post is about a much less appetizing kind of foam. You see, starting in about 2009, in the pits that capture manure under factory-scale hog farms, a gray, bubbly substance began appearing at the surface of the fecal soup. The problem is menacing: As manure breaks down, it emits toxic gases like hydrogen sulfide and flammable ones like methane, and trapping these noxious fumes under a layer of foam can lead to sudden, disastrous releases and even explosions. According to a 2012 report from the University of Minnesota, by September 2011, the foam had “caused about a half-dozen explosions in the upper Midwest…one explosion destroyed a barn on a farm in northern Iowa, killing 1,500 pigs and severely burning the worker involved.”
The foam grows to a thickness of up to four feet, and scientists can’t explain the phenomenon.
Angela Kent, an associate professor in the department of natural resources and environmental sciences at the University of Illinois, reports that “manure foaming” is “still a very serious problem among pork producers in the Midwest.” Scientists have still not been able to finger the cause of it, but “we are in the midst of a large multi-institution investigation focused on finding the cause of this very serious problem.”
Larry Jacobson, a professor and extension engineer at the University of Minnesota, reports that around 25 percent of operations in the hog-intensive regions of Minnesota, Illinois, and Iowa are experiencing foam—and “the number may be higher, because some operators might not know that they have it.”
He added that the practice of feeding hogs distillers grains, the mush leftover from the corn ethanol process, might be one of the triggers. Distillers grains entered hog rations in a major way around the same time that the foam started emerging, and manure from hogs fed distillers grains contains heightened levels of undigested fiber and volatile fatty acids—both of which are emerging as preconditions of foam formation, he said. But he added that distillers grains aren’t likely the sole cause, because on some operations, the foam will emerge in some buildings but not others, even when all the hogs are getting the same feed mix.
A solution seems to be emerging, Jacobson reports: Dump a bit of monensin, an antibiotic widely used to make cows grow faster, directly into the foam-ridden pit. At rather low levels, about 25 pounds of the stuff will treat a typical 500,000 gallon pit—the stuff effectively breaks up the foam, likely by altering the mix of microbes present. No other treatment has been shown to work consistently, Jacobson said.