Last winter I built a wooden worm bin. It has worked okay, but as the porous wood absorbed water from the worms and compost. This caused warping and made it hard to fit the sections together. I thought I’d build a plastic version, which is more common, for comparison.
The bin consists of two stacking Rubbermaid 10-gal totes. They cost approximately $10 each at the local hardware store. This system works by holding the older compost and worm casings in a bin at the bottom and then newer compost in the top bin, stacked on the first. The worms migrate from the finished compost and casings through 1/4-in holes drilled in the bottom of the bins. I drilled about seventy-five holes but may increase this at some point.
The best part about the wooden bin is that it is breathable. Worm can drown if the compost becomes too sodden. The plastic bins are impermeable and water can bead up on the inside. To avoid moisture buildup, I drilled hundreds of 1/16-in holes all over the lid (I made fun designs: a worm and an apple) as well as along the upper sides of the tote. Only one lid gets drilled.
Setup and How It Works
The lid that was not drilled with ventilation holes is set on the ground. Two spacers (I used 1-x-2-in dimensional lumber) are placed on top of the lid. When the first tote is set on the spacers, it leaves a gap for liquid to seep out of the bin and air to flow beneath it. Worms (red wigglers only; you can probably find someone in your local community willing to sell you some) and compost are added to this first bin. If you’re starting out new, check out first post I made about this subject. You can add moistened shredded paper to help build up a suitable environment. The ventilated lid can be put right on top of this first bin.
Once it builds up a few inches of composted worm casings, the second bin is placed on top, making sure the bottom of the bin is in contact with the existing layer of casings. New compost is added to the top bin now and the worms will migrate up through the communication holes over time. This allows the lower bin’s “black gold” to be harvested with less work to separate the remaining worms.
Most all vegan compost can go into the bin. Avoid meat and dairy because the little buggers can’t handle them. Plant-based scraps are great except for onions and citrus peels. One can add ground-up eggs, but we feed ours back to the chickens.
Fruit Flies and Other Growths
I’ve had some fruit fly problems, since this system requires lots of ventilation. To combat them, I’ve placed a jar of apple cider vinegar with a drop of dish soap next to the bin and it caught hundreds of flies in a few days. This is the best fruit fly solution I’ve found (and I’ve tried a few).
The compost will likely grow some mold. Usually this is fine. I would just turn the compost once a week. After the worms establish a critical mass and the bin is established, this does not seem to happen often.