A strange new growth has emerged from the manure pits of midwestern hog farms. The results are literally explosive.
Since 2009, six farms have blown up after methane trapped in an unidentified, pit-topping foam caught a spark. In the afflicted region, the foam is found in roughly 1 in 4 hog farms.
There’s nothing farmers can do except be very careful. Researchers aren’t even sure what the foam is.
“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,” said agricultural engineer Charles Clanton of the University of Minnesota. “Whatever has happened is new.”
A gelatinous goop that resembles melted brown Nerf, the foam captures gases emitted by bacteria living in manure, which on industrial farms gathers in pits beneath barns that may contain several thousand animals.
The pits are emptied each fall, after which waste builds up again, turning them into something like giant stomachs: dark, oxygen-starved percolators in which bacteria and single-celled organisms metabolize the muck.
Methane is a natural byproduct, and is typically dispersed by fans before it reaches explosive levels. But inside the foam’s bubbles, methane reaches levels of 60 to 70 percent, or more than four times what’s considered dangerous. The foam can reach depths of more than four feet.
Disturb the bubbles, and enormous quantities of methane are released in a very short time. Add a spark—from, say, a bit of routine metal repair, as happened in a September 2011 accident that killed 1,500 hogs and injured a worker—and the barn will blow.
If it’s easy to see what the foam causes, however, it’s much more difficult to understand what causes the foam.
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