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How much heat can compost worms handle?

Worms composting manure

Although the title of this post may seem like an odd question to ask, it makes sense once you start thinking about worm bins.  After all, your goal when adding biomass to a compost bin is similar to your efforts when making a compost pile, and a well-made compost pile quickly heats up from microbial action.  So, can worms stand hot composting?

Manure in worm binThe reason I started researching this question is because the manure we used to fill our second worm bin was fresher than I thought and soon heated up.  I didn't think to stick in the compost thermometer until this weekend, but suspect the manure got hotter than the 90 degrees at which compost worms perish.

In heartening news, I tossed similarly fresh manure on top of the worms in the first worm bin a week earlier, and I just noticed that those worms have moved to the surface and started to work.  I suspect the worms were able to hide at the extremities of the bin, where temperatures were lower, then slither back into the center once the first burst of heat subsided.

Compost thermometerI hope that the soaked newspaper I added to the second bin gave those worms a similar escape hatch.  (Adding carbon slows down a compost pile, which lowers the heat.)  Only time will tell whether we have to seed the second bin again, but I know that after this, I'll be careful to let manure cool down before adding compost worms.

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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I have a smallish worm bin underneath a potting table in my greenhouse so that the water that goes through my start trays is caught and reused to make worm tea. It regularly gets 120+ degrees in the ghouse down here in Texas. My worms are thriving. I think plenty of moisture is the key as it keeps the lower portions much cooler. My bin only has a few (~3") of material. I was a bit surprised how well they are doing. Wigglers are very adaptable as I originally got them out of a still frozen compost pile in Massachusetts.
Comment by eric Mon Jul 16 08:31:16 2012
There was a segment on vermiculture on Saturday's episode of Oklahoma Gardening and they addressed the temp issue, more so just because of how hot it has been lately... an instructor from OSU rigged up a bucket of ice that drips into a worm bin to help cool the worms, may not be practical if you are off campus and don't have access to industrial ice machines ;)
Comment by Phil Mon Jul 16 11:57:20 2012

Eric --- I'd be curious to hear how hot it gets in the worm bin when it's 120 in the greenhouse. Do you have a soil thermometer to stick in and see?

Phil --- Icing the worms probably isn't a sustainable solution here, but did make me laugh. :-)

Comment by anna Mon Jul 16 14:55:58 2012

I dont have a thermometer short enough since my bin is so shallow. My greenhouse spends the summer covered in 40% shade cloth only. Two weeks ago we hit 109 in the shade. So the ambient temp inside the structure would have to be similar, if not higher. I've seen my thermometer in the ghouse hitting 130 when I still had the plastic on, but I imagine its gone higher. Honestly, I was expecting the worms to be fried, but they are thriving.

I think the keys are: moisture, open top for circulation and not trapping in heat and gasses, shade (shade cloth plus under a table with starts), and plenty of shredded leaves to start to get the high carbon soil that will hold more water. Only stuff I have fed are leaves and mini donkey dung so far.

Comment by eric Tue Jul 17 14:32:47 2012
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