The Curious Case of the Exploding Pig Farms
At first, the manure was just harmlessly foaming. Only later on did things get lethal.
Hog farms in the Midwest are great big barns sitting on top of great big pits filled with a great deal of awful-smelling manure. The pigs walk about on a slatted floor that lets manure fall into the pit several feet below. Around 2007, farmers began noticing pig poop acting funny. The normally liquid mixture started producing foamy bubbles, rising up and up, past the slats, right to the pigs’ cloven hooves.
Then it got worse. Among the gases in the bubbling in the foam are two of special note: methane and hydrogen sulfide—both highly flammable. All it takes is a small spark and Kaboom! In September 2011, a barn explosion killed 1,500 pigs and seriously injured one worker. It was just the most serious in a string of barn explosions that have cost farmers millions of dollars in the past several years.HT: io9
Scientists have scrambled to solve the mystery of the exploding hog-manure foam, but no straightforward answer as emerged so far. As a matter of physics, every foam needs three components: gas, stabilizer, and surfactant. Manure is normally teeming with microbes, which produce gases like methane and whose cells can act as stabilizers. Therefore the surfactant—any chemical such as soap that lowers the surface tension of liquids to allow bubbles to form—is a likely candidate for what’s new.
Around the same time that foaming manure became a problem, farmers also started feeding their pigs more and more distiller’s dried grains with solubles (DDGS), a cereal-like byproduct of ethanol production. DDGS is full of plant fibers and long-chain fatty acids—plausible surfactant candidates. Since the US provides huge subsidies for making ethanol from corn, DDGS was cheap and plentiful source of animal feed. It makes economic sense, at least.
DDGS has been a suspected culprit of foaming manure from the beginning (one magazine called it a “pig bang theory”), but experiments are still inconclusive....MORE
