The Adirondack Daily Enterprise reported that a house recently caught fire and burned down due to the spontaneous combustion of an adjacent compost pile. Bacterial fermentation causes compost piles to heat up. This is good. That's how yard waste and vegetable scraps break down into the fertilizer we know and love. However, very large compost piles run the risk of spontaneous combustion. If the heat produced by the composting action is quite strong, and the pile is quite dry, the compost pile can burst into flames. The Alberta Agriculture and Rural Development department published some guidelines for preventing flaming compost piles. Basically, if you plan of having a 13 foot compost pile at home, you'll need to monitor the internal temperature and moisture levels. Small compost piles don't usually reach such high internal temperatures.