I started moving my composting wood chips this spring, and noticed that the middle of the pile is still frozen, but the outside is workable, why is that?

I can tell you that when we had no snow on the ground we had a -30F/-34C degree day.

  • 1
    If the middle of the pile is "frozen" you haven't got a compost pile but a rubbish heap. The middle of a properly working compost pile ought to be at about 40 - 50 C (100 - 120 F), not frozen.
    – alephzero
    Apr 4, 2019 at 22:17
  • it's only frozen on the outer layer, not the inner core Apr 5, 2019 at 3:12

1 Answer 1


I'm not sure where you're located, but it's likely the heat from the sun. If it froze during the colder months, it will take longer for the inside of the pile to thaw, whereas the outside of the pile has direct access to the sun. Once the whole thing thaws, then you'll start to see it beginning to get hot on the inside as the compost decomposes and generates heat. The frozen middle can't rot and generate that heat right now, just like food can't rot in your freezer.

  • I'm from MN USA, and I was poking in the pile, and saw some smoke come out when I dug into the pile, could the core be cooking, but the shell still be frozen as we've had some freezing nights? Apr 5, 2019 at 3:11
  • @blackthumb it’s a possibility. MN gets really cold (as I’m sure you know, haha). I’ve seen cold things steam as they warm up, but there could be a middle frozen layer. It’s hard to say for sure though without having been there.
    – Gwendolyn
    Apr 5, 2019 at 3:39
  • MN gets so cold that we get 6 months of walk out freezer. Apr 5, 2019 at 4:30

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