Feb 16, 2012

porcine foam

Once someone asked me what the next form of life to evolve would be. I said a bacteria that can live in landfills and feed on plastic. I was close.

Midwestern pig farms have begun to explode. Mysterious foams have started forming atop waste pits, and with poor ventilation, gases can accumulate. In several barns these gases have ignited, killing thousands of pigs and injuring farm workers.

Hog farms have always been bacterial breeding grounds. It is not pig shit that stinks so much as the bacteria breaking it down. The stench of a pig operation is proportional to the vigor of its microfauna, but a bacteria that farts foam may be new to the mix. The foam might be evolution in action.

Foams were first observed in 2009 and have formed in many hog barns, but only a few have exploded. Experts in agricultural gas production at the University of Minnesota have been studying the foam, and they believe it may be associated with distillery offal. Spent grains are mostly cellulose, depleted of nutritional worth, but some anaerobic strains of bacteria can break it down. Hosting such bacteria in their guts is what gives ungulates the ability to survive on a grass diet, and dinosaurs surely used the same trick.

A new anaerobic species of cellular life may have evolved in industrial hog waste, or an existing species of gut bacteria could be exploiting new opportunities in the outside world. Either way, some cellular critter in hog shit is generating copious quantities of gas, enough to create up to 4 feet of gray foam on the surface of hog slurry. Experts recommend knocking down the foam with water, but dry manure generates less odor. Controlling runoff is a major expense for farms, so they prefer to use less water, not more. Water is also a temporary solution, and outbreaks or rising temperatures can catch operators off guard, resulting in explosions.

Manure scientists are hard at work on the mystery foam. You may think I'm being facetious, but manure science really exists. Industrial hog and chicken farms require waste processing systems, pollution permits, and sophisticated emissions management. Hog farms have neighbors and odors that carry miles downwind.

Jacek Koziel at Iowa State use chemical methods and his own nose to measure and identify "compounds in the swine manure headspace." Advanced techniques allowed Dr. Koziel and his team to identify 295 airborne compounds in a 2010 study, 71 considered odorous and 16 regulated pollutants. They were able to expand the library of known swine manure gases by 44 molecules, but no one has yet determined the culprit behind the foam. Methane likely powers the explosions, but the filmy substance trapping the methane appears to be new.

Quoted in campus newspaper the Minnesota Daily, professor Charles J. Clanton said, "you have two identical buildings sitting next to each other with same management, genetics, diets, etc. One foams, and the other does not." That suggests differences in microfauna and the possibility that a new species of bacteria has evolved but is still spreading from barn to barn and farm to farm.