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-