Worm Composting Garage Bench


April 14, 2010

My wife is an avid gardener. Along with that she spends a lot of time composting various leftover yard waste and kitchen scraps out in the big pile in the backyard. During the winter its hard to do any real composting since any organic matter freezes within minutes of being dumped (we live in Wisconsin).

Last winter Anna discovered a novel solution to this conundrum: composting in the garage with worms doing all the work. Initially I thought this idea was completely nuts but to Anna's credit it actually worked well. Its amazing how much the worms can go through in a week. One problem though is keeping the critters from freezing out in the garage during the winter.

Our garage isn't insulated so it can fall below freezing out there on really cold nights (when its less than zero Fahrenheit outside). Our solution to keeping the worms warm and active was to make an insulated container to house them in.

Originally I built a 3' by 3' by 3' container to house the worms, which worked well for the initial vermiculture experiment. Eventually Anna wanted to expand her worm empire so we needed more space.

General Wormbox Design

I had previously bought and assembled a wooden workbench from Menards (Workmaster was the name I think, basically a kit of 2" x 4" and 2" x 6"). It was a two level design and my plan was to build an insulated box out of the lower shelf level using some plywood, spare 2"x4"s and R12 insulation.

Exhaust Fan

Along with the idea of the enclosed worm box I wanted to add an exhaust fan. The reasoning behind that was that in the summer it would be useful for keeping the temperature cooler and it would also be a way to vent any "extra ripe" compost fumes from any decaying food out of the garage.

I figured a standard clothes dryer exhaust fan would be perfect to vent the fumes. I picked up a low profile one that somewhat matched our garage siding (brown in color). The next step was to drill a hole to install it. I went with the cheap adjustable holesaw option since I don't have a full set or real hole saws. Those bits don't last but I only needed to drill one hole.

For the actual exhaust fan I happen to have a bunch of random cooling fans that I saved from the scrape pile at work. I used a piece of Plexiglas to mount a 12V 2" x 2" fan inside a 4" peice of tin ducting. I used a 12V "wall wart" AC adapter to power the fan.

Wormbox Framing

To build the enclosed part of the wormbox bin I really didn't have a plan. I just bought some spare 2" x 4" to make a frame to attach some basic 1/2" plywood. While i was putting the frame together I forgot to take pictures so I don't have to much to post for this step.

I mounted the piece of tin ducting with the exhaust fan in the upper, rear, left corner of the enclosure. The general idea was to have the air flow come in from the bottom right and flow up to the exhaust fan in the upper left (an idea blatantly stole from computer case designers).

Wormbox Insulation

After the basic frame and plywood was done I went through two tubes of sealant filling in the cracks of the enclosure. Then I got out the roll of insulation and my staple gun and started insulating the bench. Inside the box and underneath it doesn't look pretty but I am sure the worms won't mind.

Completed Garage Worm Composting Bench

With active worm bins!

Here is the completed bench. On the left side of the bench you can see the tin air exhaust outlet. I have not hooked up the exhaust hose yet as I was still repositioning the bench when I took this picture. I left the bench lower shelf hang over the post so I could use that as an outside as a shelf (i.e. for my stock of Diet Mt. Dew and Ginger Ale).

To keep enclose the front face of the wormbox I used an old, blue comforter that had been retired due to extreme funkiness. I had a spare 2" x 2" which I secured to the front face of the bench to drape the blanket over. Unless the worm bins are being actively moved around the blanket hangs down and the bench top can be used for normal garage stuff.

To keep the wormbins warm in the winter the plan is to use a pad heater (plugged into a ground fault outlet). Eventually the plan is to add a temperate controller so we don't have to constantly check if the bins are getting too cold during the winter.