Up here in Manitoba at 51 degrees Latitude on the Canadian Prairies, climate extremes are the norm.  We get 100km winds semi-regularly, summer temperatures of 40C and winter temperatures of -40C.  In summer we are prone to tornadoes while in winter, we’ll get slammed with blizzards which routinely drop more than 30cm of snow at a time. Frost penetrates almost 3 meters in a cold season, and by winter solstice, we get a scant 8 hours of light during the day.

 It isn’t boring!

One of the challenges these climate extremes creates is composting during the winter months.  Kitchen waste left outside becomes a huge mass of frozen material that is strewn about by magpies, dogs, and other scavengers.  In spring, what remains becomes a stinky, wet, anaerobic mess, until it can be formed into a proper pile. Plus maintaining a path through deep snow just to have a place to put kitchen scraps takes the joy out of composting.

In summer, I am always running one or more ‘hot compost piles’ for yard waste and kitchen scraps, but I don’t typically add kitchen scraps after the 2^nd or 3^rd turn.  As a result, this year I also established a large bathtub of red wriggler composting worms which get most of our kitchen ‘waste’. This bin is right next to the house, which also means less of a trek when emptying the scrap bin. 

Unfortunately, red wigglers are not lovers of the cold.  

So my challenge was to create a simple solution which would not only keep my red wigglers warm through the winter months, but which would also permit me to compost the kitchen materials year-round—ideally without a lot of extra fuss or energy expenditure. 

The solution came to me one day when I was considering ‘energy sinks’ from our house.  Our water table is very high here, and since our house has a basement, it is always humid indoors.  As a result, we are constantly exhausting warm, moist air with a fan which runs in our bathroom.  This means that there is a steady flow of warm, humid air ‘sinking’ from our house at the exhaust end of this bathroom fan.  The bathroom exhaust is also adjacent to the dryer exhaust, so that whenever the clothes dryer in on, this additional heat is ALSO lost to our house. 

I happened to have a bunch of reclaimed cedar boards from a lumber lot I purchased at an auction this past summer.  I also had a significant amount of rigid insulation which I had salvaged out of the waste stream from a construction project.  Using these ‘upcycled’ materials, I knocked together an insulated enclosure for my bathtub vermicomposting bin. The exhaust from the bathroom and dryer are ducted into this enclosure and exit from a vent-pipe in the roof of the new enclosure. 

The roof is friction-fit and lifts up for when I need to add kitchen scraps to the bin. By the bathtub’s drain, the bin’s side comes off entirely to permit me to access the ‘worm juice’ with relative ease. 

Two weeks ago—before I had built my worm-bin enclosure, the red wigglers were alive but sluggish. They certainly were not processing my kitchen waste efficiently, and had likely stopped reproducing in their cold, near-dormant state.  Yesterday I went out to have a look.  Pulling back the layer of straw which I use to cover the worm’s bedding, I was thrilled to see a happy, writing mass of red wigglers making short work of last week’s kitchen waste.  

Hopefully the single bathtub will provide sufficient volume for me to make it through the winter without having to remove any material—that way when spring comes, I’ll have a massive supply of worm casts when it comes time to plant my garden. 

This was a fun, gratifying project which I suspect would be worth pursuing for anyone looking for a composting solution in a cold climate.  Modern houses tend to have HVAC (Heating, Ventilation and Air Conditioning) systems which ALSO are constantly exhausting warm air from the house…why not consider using that residual heat once more before it is lost to your system?