system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If you have a pile of mulch/woodchips/etc and leave it long enough it can start to smoke. How?

I understand that it's the breaking down of the organic material that's generating the heat, but how in the world does it generate enough heat to start to smolder?
gpt
A large enough pile will be generating heat all through it, and the stuff in the middle has nowhere for the heat to go, so it builds up. Eventually, you'll hit the smoke point for something in the pile (the wood, the resins in the sap, small children, you know) and voila! Smoke!