Wow...
http://arstechnica.com/science/news/2012/03/mysterious-hog-farm-explosions-stump-scientists.ars
http://arstechnica.com/science/news/2012/03/mysterious-hog-farm-explosions-stump-scientists.ars
Mysterious hog farm explosions stump scientists
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.
Theres nothing farmers can do except be very careful. Researchers arent even sure what the foam is.
This has all started in the last four or five years here. We dont 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.
...
Disturb the bubbles, and enormous quantities of methane are released in a very short time. Add a sparkfrom, say, a bit of routine metal repair, as happened in a September 2011 accident that killed 1,500 hogs and injured a workerand the barn will blow.