Winter Vermicomposting-1-02-12

Initially I was worried that my coffee grounds pick-up commitment was going to end up being a real hassle this winter. As it turns out, though, it’s been more of a blessing than anything – and I have a sneaking suspicion that this could end up being my most successful winter vermicomposting season yet. One of my challenges in past seasons has been the lack of a decent supply of composting “fuel” materials to add to my bed – especially by the time late January and February rolled around (when I needed them the most). With a steady supply of grounds that certainly won’t be the case this year.

I don’t know what it is about coffee grounds – well ok, it’s likely the small particle size (thus large total surface area) and nitrogen content – but they seem to be the “ultimate” material for getting a heap to warm up. That being said, they definitely are not an ideal material (for vermicomposting anyway) when used alone. In my experience, they tend to overheat and/or dry out, so it usually takes some time, even in outdoor beds exposed to the elements, for them to become a good quality worm habitat. One of my goals with with this winter system has been to see if I can make the grounds “worm-friendly” more quickly by mixing them with other materials.

On a whim, I decided to try something quite different right off the bat. Rather than burying the grounds down below where the worms are, I’ve simply been dumping them on top and gradually mixing them in with the thick layer of straw (originally added for insulation) using a garden fork. I’ve been making a bit more of an effort to bury the food wastes, but they are still being added up in the straw zone (above where most of the worms are).

So far, this seems to be working even better than expected. Rather than ending up with overheating down in the worm zone, it’s like I’ve created a thick, heated blanket over top of them. Over time, the lower zones of the “blanket” will undoubtedly cool off and become food/habitat for the worms as well, so I suspect that conditions in the bed will actually improve as winter progresses (not decline as they often have in the past).

Anyway – if you want to see the bed a bit more “up close and personal”, you can check out the video I made:

Stay tuned!
Will likely provide another update in a couple of weeks.

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    • Steve L.
    • January 2, 2012

    Your shared experience of winter vermicomposting should really help those that want to overwinter their worms when an indoor, fossil-fueled heated space is not available. For instance, I had several bucket, tub, and RM bins going outside this year as I worked on expanding my herd, but when it came time to winterize them (they sat under the edge of the back porch and under the porch roof overhang during spring/summer/fall) I did not have a heat-protected space to keep them from freezing during a winter cold snap. (B… you have “real” winters, we in the maritime pacific northwest get cold “snaps”) So, I scooped the worm-mass layers out of each bin and dumped them into my traditional wire-ring compost heap, added a layer of food source, and a thick, dry layer of leaves.
    It’s really cool to see that only a layer of tarp over your winter herd keeps enough heat in during your cold weather. I agree that CG are a great heat source for composting, but they do require water to degrade and be food for the worms. My experience is that I usually have to add water during the process as their heat dries out the area. Nice idea on a slow-release snow layer for moisture.
    Thanks for the video and post, and all the experience shared.

    • Rich Yarger
    • January 2, 2012

    Great new video Bentley! I’m curious to know just how deep the windrow is.

    • Dave
    • January 3, 2012

    Love the video. Especially the use of text titles rather than audio narration; I can watch without bothering anyone else in the room!

  1. STEVE – Sounds like we’ve had similar issues with coffee grounds! It’s like a very tricky yet almost magical material for composting! You are absolutely right about the moisture – that is the KEY!
    Just to be clear here, what’s between the main worm zone and the cold is a fairly thick straw + coffee grounds + food waste layer, plus a double tarp layer. I even added a bunch of snow on top yesterday since we were expecting some REALLY cold weather today (the weather has been really weird as of late – supposed to be fairly mild for the rest of the week).
    RICH – I don’t know if the bed would be as much as two feet in height from ground level. Based on the volume, I am quite honestly surprised that it’s heating up as much as it is. We shall see how it performs once the really cold weather arrives I guess.
    DAVE – Glad you liked it! It was easier to create (no worries about multiple takes etc), and I agree that it eliminates the issues that can be associated with trying to watch videos when others are around (something I know all about myself – haha).

    • Ready Red Worms
    • January 18, 2012


    I live in central Arkansas. We don’t get harsh winters that often. We can get times where the temperature stays below freezing for a week or so. So my experiment was to start a rubbermaid bin loaded with damp rabbit manure and a pound of red worms. I buried the bin about three quarter into the ground and then piled a couple of feet of leaves over the top. If you’d like I let you know how the worms and processed bedding(food) looks when spring comes around.

    See last winter I placed a large pile of harvested casting covered with leaves on my garden. When spring came around the castings and leaf mold near the ground was loaded with worms of all sizes. I took the leaf mold and started several rubbermaid bins.

    Now I can’t say that we don’t ever get hard long freezes here. Although it is seldom, one year the castings(bedding) in my refrigerator bin froze solid.

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