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
advance!

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!

Written by Bentley on April 3rd, 2009 with 4 comments.
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