According to the EPA, "Yard trimmings and food residuals together constitute 27 percent of the U.S. waste stream." If only we composted all that crap, we could virtually eliminate the need for chemical fertilizers, repair damaged soil and absorb air pollution. And to think, you can accomplish all that simply by replacing your backyard with an enormous pile of rot!
So what's the downside? Two words: spontaneous combustion.
"Well, at least I don't need to edge now."
There you are, marveling at how you can save the environment just by tossing your banana peel into the yard, when OH MY GOD YOUR NEIGHBORHOOD IS ON FIRE. See, the raw materials in compost piles attract bacteria, which is good, because those are the little guys that break down your (sometimes actual) shit and turn it into plant food. But since we can't see them, it's easy to forget that they are in fact alive, and any living, moving things will create heat.
As more and more bacteria crowd together, reproducing in a big ol' bacterial orgy, they raise the core temperature of the pile. Then, needing to cool down from all that humping (and presumably rinse the taste of rotting garbage from their microscopic mouths), they suck up all of the pile's remaining moisture, effectively converting your compost into kindling. And since, like reality TV stars, bacteria lack the necessary gray matter to foresee the consequences of their unsustainable lifestyle, they continue down this path of self-destruction until the increased temperature of their surroundings results in an all-consuming compost bonfire.
It's like Woodstock, only not quite as dirty.
The biggest cause of spontaneous compost combustion is people being too lazy to turn over their compost heap every once in a while so some air can get in there and cool it down. Apparently this is no small problem, because between 2005 and 2009, the National Fire Protection Association reported 5,250 "outside non-trash fires" started by spontaneous combustion, and of those, 28 percent were ignited by organic material. Just so you don't have to break out your calculator, that's 1,470 spontaneous combustions caused by people not wanting to mess with the icky stuff in the backyard. And it's quite easy for a fire that started in your compost heap to spread to your house or even your neighbor's house, making for a lifetime of truly awkward meetings by the mailbox.