As we approach the end of our second winter using the insulated red wiggler composting worm setup, I thought I’d take a moment to report on the success of the project, and make some additional recommendations to anyone considering something similar.

Overall, the project has been a resounding success. Not only have the worms survived though one of our coldest winters in recent memory (-30C for almost a full month), they have thrived!  It is astonishing how much organic material they are able to process. Our household of four easily makes it through an entire winter without filling the bathtub to capacity, in spite of the fact that I likely put 15 litres of kitchen waste into it every week.

In order to harvest worm-casts, I simply restrict my feeding to one side of the bin. Over time, nearly all of the worms migrate to the area where new food is being deposited.  At that point, I am able to remove almost completely clean worm casts from the OTHER side of the bathtub-bin (I do screen the casts in case there are worms in it, but I have come to believe this step is likely unnecessary). Following a harvest, I put some new bedding material in and begin feeding exclusively on THAT side. Repeat.

There ARE several things I have learned which might be of use to anyone wanting to undertake a similar project:

1) Raise the tub more. In my case, the tub drain is approximately 25cm (10 inches) off of the ground. While this technically “works”—it doesn’t permit me to keep a very large vessel underneath to collect the ‘leachate’. In winter, when emptying leachate isn’t my favorite task, it would be nice if I could put it off for an extra couple of weeks. In the future, I will likely raise the tub another 20 cm-or-so in order to accommodate a larger leachate container.

2) Use smaller hardware cloth to rodent & shrew-proof! Knowing that a nice, warm spot full of worms and other food would be irresistible to little critters, I placed my cinder-block foundation on ABS hardware cloth.  Both winters, now, shrews have infiltrated the insulated bin and have had a few days of heaven before I discovered their presence and fed them to my outdoor compost pile! If you are building a shrew-proof enclosure, I suggest NO GAPS LARGER THAN 6mm (1/4 inch).  If you DO get shrews, I had quick success with pre-baited ‘snap-traps’.

3) Space the enclosure further from the house. Since I was harvesting ‘waste heat’ from my bathroom and dryer vent, I sited my bin quite close to the house—approximately 25 cm (10 inches) away. While this is desirable from the perspective of minimizing winter heat-loss through the ducting, it was a nuisance when it came to initial installation. I suggest siting the bin to approximately 50 cm (20 inches) away from a house/structure so that it is easier to attach ducting and access behind it, if you need to.

4) Watch the bedding material. I typically give the worms whatever I have on hand for ‘bedding material’—straw, newspaper, cardboard, planer shavings, etc. Once I added a bunch of oak planer shavings and shortly thereafter the worms initiated a mass exodus! I can’t be 100% sure it was the oak shavings that caused their displeasure, but I will throw it out there that it is worth keeping track of what you are giving them and paying attention to whether they seem happy with it or not!

5) Consider snow-clearing when planning leachate collection: My insulated bin is constructed in such a manner that I can take the side right off in order to access the leachate. This means that when there is a lot of snow against the bin, I have to shovel or risk the side not mating properly when I re-insert it (read: “shrew access”). I suspect an access hatch ABOVE ground level would be desirable, if you had the height to work with.

I heartily encourage anyone in a cold climate who is looking for an effective way to compost in the winter months to explore something like this sort of set-up.  I know there are people who use red wigglers right in their home, but it is worth it to me to have the material outside--closer to where I need it--and to avoid the risk of fruit flies, odors, etc., that are difficult to completely avoid if composting in your home.