How Vermicomposting Works

Building a Worm Compost Bin

Worm bins come in all shapes and sizes. If you're building your own, cover the basic elements, but then the rest is up to you and your imagination.
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Worm composting begins with a proper bin. You can build your own or invest in ultra-deluxe, multi-tiered, screened-in, self-sifting ventilation systems for hundreds of dollars. Another option is to find a plastic tub and poke holes in it. Like many activities, worm composting is limited only by your imagination. For example, the community composting system at Common Ground Athens in Athens, Ga., was built by yours truly, using a salvaged bathtub. For temperature and moisture levels, however, a wooden bin is best. There are only a few requirements for a good worm bin:

  • More surface area than depth (wide and shallow)
  • Air holes in the bottom
  • Low sides for ventilation

If kept properly, your worms will not crawl out of the bin. Worms are a non-migratory species, which means that they won't go anywhere if they don't have to. They're also afraid of light. If you open your bin during the day, any worms at the top will dive down below the surface. They have no reason to leave if there's food and comfortable bedding. If you are truly afraid of your worms escaping, you can build in a layer of mesh wiring around the air holes. Even if you're not afraid of your red wigglers wiggling away, keep a lid with air holes on the bin and a layer of black plastic over the bedding (also with air holes cut in it) to keep light and other animals out.


The next thing you need is bedding. Shredded paper and leaves work well. This means that you can compost your office paper as well as your kitchen waste. Bedding needs to be lightly moist, but not dripping wet. Worms breathe through their skin, so having the right level of dampness and air flow is the key. But beware -- if it gets too wet in the bin, the worms can drown. The best way to wet the bedding is to fill a separate bucket with water. Then dunk your bedding, by the handful, in the water and then squeeze it out until it's barely dripping. Next, pull the bedding apart before putting it in the bin to create air pockets and passageways for the worms. Finally, throw in a couple of handfuls of dirt and leaves from your back yard to give them some grit and good bacteria. Worms are similar to birds in their digestion: They have gizzards that require grit to aid in grinding up their food. Soil and other gritty organic waste, such as coffee grounds, can help with this process.

Where should you keep your bin? Anywhere that's safe from other animals and extreme temperatures. This can be a basement, patio or even your kitchen. If you bury the food below the bedding properly, the only smell coming from the bin should be that of fresh, damp earth. If your vermicomposting system is healthy, the decomposing food will not smell or attract flies. Remember, worms can freeze or even burn, so your worm bin should be kept in temperatures ranging from 40 to 90 degrees Fahrenheit (4.4 to 32.2 degrees Celsius). If it gets colder or hotter, try to bring them inside.

Once you've found a good location and you have your worm bin and bedding all set up, it's time to dump in the worms. They'll need a day or two to adjust to the new space before you begin to feed them. Find out which foods will make your worms thrive, as well as the foods that will kill your worms on the next page.