Spontaneous Combustion in the Wild?

My Blog friend Katana remarked in my last post about the California fires that dead plants can generate gases, and then, when the desert heat gets to it, “poof,” up in smoke it goes. I’m not sure anything in nature works exactly like that, but Kat says that all Californians know this. Hmmm. Perhaps its just Southern Californians that know it, since I lived twice in that state, but mostly in Northern California.

Regardless, being an extremely curious fellow, especially when it comes to nature and natural phenomena, I could not let Kat’s assertion go unresearched or unchallenged. The more I thought about what she said, the more doubtful I became. Within minutes I could stand it no longer. I had to scratch this darn itch planted in my brain by this Kat woman. I was compelled to get up and sit back down in front of my buddy, Mr. PC, and vigorously “hit the Net.” I search-engined the heck out of spontaneous combustion and soon, I came to a conclusion.

Even without Dr. Google I know that plants and animals can generate their own heat during decomposition. When I was a kid in Michigan I gloried in making rich humus in our compost heap. I’d mix in grass clippings, kitchen waste, leaves, sawdust, coffee grounds, whatever I could find, as long as it was of plant origin and biodegradable; and then I’d throw in a couple shovelfuls of sand and clay, add water and toss liberally.

Once the decomp started, even on frosty autumn mornings, the heat built up on the inside of that heap of rotting compost was surprisingly warm, even hot. The thing is, I never once saw a decomposing plant—or a whole heap of them for that matter—erupt into flames, no matter how hot out it got. So I have to say Kat, I have my doubts on your claims that rotting plant life in the wild can spontaneously combust.

Nope, there’s only one way in the wild that dead cellulose—which basically is what all plant material is—can burst into flames; and that’s by way of a spark introduced by some outside source. UNLESS! I say that because I WAS able to find that SOME biological materials CAN indeed ignite by themselves. Here’s what Wikipedia lists as SOME natural materials that CAN spontaneously combust:

· Haystacks and unprocessed cotton may self-ignite because of heat produced by bacterial fermentation.
· Grain dust in a hot metal silo can explode violently, destroying the structure.
· Boiled Linseed oil in a partially confined space (such as a pile of oil soaked rags left out in an uncovered container) can evaporate leading to a subtle tremendous buildup of heat and thus ignition. Experiment by Rob Bicevskis
· Tall stacks of rubber artifacts, such as tires and some types of mattresses, can spontaneously combust from heat buildup caused by friction.
· Coal can spontaneously ignite when exposure to oxygen causes it to react and heat up when there is insufficient ventilation for cooling.
· Pistachio nuts are highly flammable when stored in large quantities, and are prone to self-heating and spontaneous combustion.

Okay, so I was unable to find any instances or claims of spontaneous combustion in the wild. Therefore, I must assume from my own experience with rotting plant life, and I have plenty, that such a thing in nature is an extremely rare thing, if it ever happens at all. The haystack example is the closest thing, and of course that is manmade.

For bacteria to have a chance to build up the kind of heat and combustible gasses that would result in ignition there must be both moisture AND dryness—moisture on the inside of a very dense amount of rotting cellulose, along with dry conditions on the outside to overcome the dampening effects of the internal moisture. It’s just not something that would normally happen in nature.

Actually, I did once witness something similar to spontaneous combustion, although it wasn’t by definition "spontaneous:"

In Japan one still, extremely sunny February morning I sat relaxing on my rear porch drinking coffee after a hard night of repairing Air Force cargo aircraft on the Yokota A.B. flightline. We lived in a quadplex and our place was on the end on a corner lot, so we had a huge yard. At that time of the year that vast expanse of grass was brownishly dead, very short, smooth and dry. It was still early enough so that the morning’s dew had not yet evaporated from the ends of each miniscule blade. The temperature was in the mid 50s, so it was pleasantly refreshing out there on my little garden porch.

Strangely enough, I remember the sun being so bright that it actually hurt my eyes to look at the grass, since the millions of dewdrops on it were reflecting the sun’s light like I had never seen before. Even sitting in the shadow of the house I had to shade my squinting eyes, so painfully dazzling the reflection.

Then, I thought my long night was making me see things. First, I saw an unlikely wisp of smoke at the far corner of the yard over by the sidewalk near the street. From that tiny wisp the grass began to turn from light tan to a patch of dark black. Subsequently the black patch began to spread out from near the sidewalk as fast as a man can jog. I didn’t see any flames at all, just that flow of charring grass growing outward like spreading water on a flat surface.

I got up and cautiously walked out to investigate. The charring flow approached me like a liquidless black flood. I could hear it quietly whisper as the tiny dead grass tendrils were consumed in this flashover phenomenon. In less than 10 seconds my entire yard and all my neighbor’s yards were blackened. I looked around me and saw the same thing happening up and down the street. Thousands of square feet of inch-long dead grass, as far as the eye could see, had turned to charcoal in a few minutes, yet there was no smoke and no flames—just this blackness that quietly flowed across the ground.

Of course I figured out fairly quickly what had caused it. The drops of dew had acted as millions of magnifying lenses, and when one would focus the sun’s rays perfectly on a dry piece of grass, “poof,” it would ignite.

The interesting thing to me though, is how the grass burned, without flame and smoke. At that time of the year it was more tinder than grass, which is why it ignited so easily in spite of the cool temperature and the morning wetness. In fact, the dew did two things: it started the flashover AND kept the grass from burning too hotly. It could only get hot enough to ignite, char and move on. Definitely one of the darndest things I’ve ever seen.

But, as I said, it was not spontaneous combustion.