We had some pretty serious flooding recently in western Washington. It's cold, wet, has been raining like crazy, and big parts of the state were under several feet of water. So what should farmers be on the lookout for in the next few weeks, as the rain and temperature continue to fall?
That's right: spontaneously combusting hay bales.
It turns out that the waterline in many areas was high enough to soak big piles of hay bales, stockpiled to feed livestock through the winter. And that water carries microbes, which get lodged into the hay and remain when the water level drops. The microbes consume the hay and release heat, which builds up in the bales because they're bound tightly and are fantastic insulators in the first place, let alone when they're stacked in huge piles. It doesn't even matter that it's colder than hades out here.
In any event, this heat builds up high enough to cause the hay to smolder and eventually catch fire. Apparently this can happen at internal temperatures as low as 150 degrees Fahrenheit.
An amusing footnote is how an agroscientist at the University of Washington recommended to check the temperature of hay bales: stick a crowbar in them, and leave it for two hours. If the crowbar is warm when you pull it out, separate the hay bales so the heat can slowly dissipate. If it's too hot to hold, call the fire department immediately. Because at that point, the bales are smoldering enough that if you were to pull them apart, you'd just dump a whole bunch of oxygen on the embers and cause the whole pile to go up in flames.
Earlier this year they put down mulch in a bunch of the flower beds around our building. There was a big pile of the stuff in the corner of the parking lot, and every once in a while you could drive by an see small flames in different areas of the pile.
Oh man that's awesome.