What to do with a mature vermicomposting system

Here are some good questions from Liz:

I am new at this worm composting and find it very
fascinating but, there is so much information out there that maybe I
missed the answer… my question is after the bin is full and all the
food waste has decomposed do I just dump the bin with all the
wonderful fertilizer in my garden with the worm as well or do I need
to do some fishing?? By the way I love your website it has so much
helpful information. I just thought of another ?? Do I dump the soil
that comes with the worms into the in to the compost bin as well?? My
mind is spinning with all the information out there that I can’t think
straight help! Look forward to reading your email. Thanks in

Hi Liz,
When your bin is full, and much of the material has turned into a dark compost, it is definitely time to start a new bin (assuming you want to continue vermicomposting) or multiple bins for that matter. You can either remove any leftover (undecomposed) bedding/food or simply leave the system to sit without feeding for a while longer. If removed, this material can then be added to the new system(s).

You can of course simply dump the contents of your bin in the garden, but I’d recommend separating the worms from the compost as best you can. There are a number of different ways you can do this. A very common low-tech approach is called the “light harvesting method”. This works particularly well outside on a nice warm, sunny day, but indoors under bright lights should be fine as well. Start by dumping the contents of your bin out on a plastic sheet and (if indoors) positioning your light over top. Leave the heap to sit for at least a few minutes (the longer the better) to allow the worms to start moving downwards. If it is really wet, you may want to actually let the material sit for a few days (obviously not going to be an option if you are doing this in the middle of your living room – haha).

Next, you simply start moving material off the top of the pile, creating a second heap of (hopefully) wormless compost. Any worms you come across can be put into a container or the new bin (for best results, this system should be ready before you start harvesting the first one). Eventually, you will basically be left with a writhing mass of worms down at the bottom, and a separate pile of compost. Aside from the missed worms, there will also be plenty of worm cocoons and baby worms left in the compost. You can either consider these a loss and start using it in the garden, or you can let it sit for even longer, perhaps with some food waste up top to lure your baby worms that have hatched. The food waste zone can then be removed and added to a new system.

Another approach you might want to try out is what I’ve referred to as the “garbage bag harvesting method“. You basically set up a new system (letting it age like a fine wine – haha), then put a perforated piece of plastic over top of the material in the new bin – on top you add material from the old bin. The worms will then migrate downwards into the new system. This method can take longer than the light harvesting, but it allows you to go do other things. You certainly don’t need to use perforated plastic either – anything that will allow worms through, while being able to support the material above (when it’s time to lift it off) will be fine – an old onion bag, mesh/screen material etc.

You might also want to try out my vermicomposting trench method, and simply dump everything in there (once a worm-friendly habitat has been created, of course). At the end of the season, you can then take some worms from your trench and start a new indoor bin.

Ok, moving on…

When adding worms to a new system, I definitely recommend also adding the material they came in, UNLESS you are trying to salvage a handful of surviving worms from a shipment that has gone awry. You definitely don’t want to add lots of dead and dying worms to a new vermicomposting system – this can create a chain-reaction of worm death, quickly wiping out the entire population (especially in enclosed plastic ‘bin’ types of systems).

Generally speaking (assuming no major issues with the worms), this material that comes with them will help them to get settled in. They can remain in it for as long as they like, rather than being forced out into the new environment.

Anyway, I hope this helps, Liz!

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    • jennifer
    • April 5, 2009

    Awsome, my question is similar.

    When selecting a soil type to use, this is important for me because I will be growing in self watering container buckets, how should vermicompost be mixed into the soil? Count it as humus? Fertilizer? I can assume it wouldn’t be the sand or clay. I was thinking of not seperating out the cacoons or tiny babies and hope they’ll be benefical for the plants in the bucket.

    My bin is small and has only been going for a few months now but I want to use what I have and start again, maybe make a second one. Build up reserves for next spring.

  1. Liz,
    My bin matured very quickly. I had already started my EXTREME bin so,
    I screened out a few inches of of my bin then I returned the castings and alot of cocoons back to one side of the bin. I then put 1/8″ screen to seperate the sides. I loaded up the unfinished side with fresh food hoping the hatched worms would migrate to the food side. Well…
    they sure did, a lot of them! I keep putting the smaller worms in my big bin.

    • Bentley
    • April 28, 2009

    JENNIFER – If you used about 20% vermicompost by volume you should see really good results.

  2. Heya!

    I thought your blog is super informative. I have been doing some research online about starting my own vermicompost system. Then I found yours!

    One question still bother’s me though, I thought of building my own multi-tier system but that’s the problem I don’t know how it works or how I should design it.

    I mean.. I saw a video once and I noticed there are some mesh that borders between the stack. Does this mean we leave all worms at the bottom first, then fill leftovers on top so they will go up??

    Aw…. I’m clueless.

    My real question will be, how does the multi-tier worm bin works.


    Have a wormy day 🙂

    • E. G.
    • April 20, 2011

    I no longer can have my vermicompost bin. What do I do with the worms? (If I cannot find someone who goes fishing?)


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