Wooden worm composting (or vermicomposting) bin

My long term plan is to do my worm composting outdoors. For that I decided to start with a wooden bin. Its dimensions are 24" across the front, 18" thick, and 12" high. The 24"x18" gives me a 3 square foot surface area. This is necessary since I first estimated I would have 3lbs of waste per week, the rule of thumb being 1 square foot of surface area per 1lb of waste per week. Click here for complete construction details. I later realized I actually produce around 5lbs of waste per week, necessitating a second bin.

Sitting in its first home under the kitchen table. Note the use of casters (wheels) to make it easy to move around indoors. The plastic bag to the left contains extra strips of newspaper for bedding.
Size comparison between the temporary black bin and this wooden one.

The bin is painted glossy white to reflect the sun (when it's outdoors.) I used exterior type latex paint because the can said it resists mildew. I painted the inside surfaces of the bin too as I wanted to reduce moisture damage to the wood.


Since this is designed to be outdoors, ventilation is specially important. Two key points to keep in mind is that hot air rises and that the south side faces the hot sun.

This box has holes on two sides. The holes on one side are high up, and since they are high up, this is where the hot air will be. Since the hot air is rising, and there is a cover on the bin, it will be forced to flow out these holes. The holes on the other side are lower down. As the hot air flows out the high holes, new air will be pulled in from the lower holes. So the side with the low holes should be facing north. This is because the bin is shading that side from the sun (which is in the south.) This means that this cooler air will be pulled into the lower holes. The following diagram illustrates this.

Fly screen is attached to prevent flies from getting in. Fruit flies and smaller insects can still get in, but if the waste is sufficiently buried then this is not a problem anyway.

Moving outdoors

On July 3, 2006, with the modifications illustrated below, the bin was ready to move outdoors.

... and in it's new home in the shade.
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