Step-by-Step Vermicomposting

Small but mighty, worms can help transform food waste into high-quality compost that’s rich in nutrients.

| Spring 2017

  • Many kinds of worms break down garbage, but for vermicomposting, red worms (Eisenia fetida, or “red wigglers”) are best and can be easily shipped to your home.
    Photo by Fotolia/Danie Nel
  • An array of kitchen scraps can be added to a worm bin, such as vegetable peels, leaves, chopped ends, spoiled fruits and vegetables, grains, dairy, and even crushed eggshells.
    Photo by iStock/Grahamphoto23
  • In about 6 weeks, you'll see noticeable changes in the bedding.
    Photo by Fotolia/TwilightArtPictures
  • Extensive decomposition takes place as more of the bedding and garbage is converted to earthworm castings.
    Photo by iStock/zerocattle
  • The end result is a wonderful fertilizer for your container plants and compost for your garden.
    Photo by Fotolia/kolidzei
  • Don't add meat, bones, pet feces, or too much citrus or other acidic items to your worm bin to avoid harming the worms or producing unpleasant odors.
    Photo by iStock/rbirch1
  • Keep your compost at the appropriate temperature, moisture and acidity levels, and ventilation for the best results.
    Photo by Fotolia/savoieleysse
  • Worms need moisture to live. Add water to bedding as necessary to maintain uniform dampness, but avoid standing water.
    Photo by iStock/Grahamphoto23
  • Red worms convert waste best at temperatures between 59 and 77 degrees Fahrenheit, but they can also plow through garbage in a basement bin with temperatures as low as 50 degrees.
    Photo by iStock/PhillDanze

Composting outdoors is wonderful, but it requires space and warmer temperatures. Just because it's still chilly out or you don’t have much outdoor space doesn’t mean you have to send your kitchen scraps to the landfill. You can easily compost indoors with helpful, wiggly worms.

Using earthworms and microorganisms to convert organic waste into black, earthy-smelling, nutrient-rich humus is known as “vermicomposting.” The whole vermicomposting process is simple, and it results in wonderful fertilizer for your container plants and compost for your garden.

Vermicompost is the compost you get from a worm bin system, which includes both castings and decomposed matter. Castings are the nutrient-rich waste that worms create. This waste is excellent as a top-dressing fertilizer for container and garden plants. Along with worms, a vermicomposting system has naturally occurring microorganisms that help decompose kitchen scraps and, over time, the worms’ organic bedding material.

Worm Bins

A variety of containers — including commercially made vermicomposting units, homemade wood or plastic boxes, and galvanized garbage cans — make satisfactory bins. The secret to an odor-free bin is plenty of oxygen. To let air in, the container must have holes in the top, sides, or bottom. To keep flies out, cover the air holes with mesh. The ideal worm bin is usually quite shallow at no more than 12 to 18 inches deep — the more surface area, the better. The size of your bin depends on how much kitchen waste you produce — assume a few pounds per week per person. It’s not at all an exact science, but you can plan on about 1 square foot of surface area for each pound of garbage per week. We estimate that a family of four will produce about 10 pounds of kitchen waste per week, requiring a bin with a surface area of 10 square feet. I recommend a worm-to-daily-garbage ratio of 2-to-1. A family that produces 10 pounds of food waste a week, or about 1.4 pounds a day, will want to start with just under 3 pounds of worms.



Because food preparation is done in the kitchen, the most convenient location for a worm bin might be there, too. An outdoor patio a few steps from the kitchen is an excellent location if it’s not in direct sun. Apartment dwellers often find that balconies are a perfect spot for a worm bin and a small container garden. A well-ventilated garage will work if it never sees freezing temperatures, and a basement is fine if it’s not too inconvenient to deposit food scraps there.

Worm beddings hold moisture and provide a medium in which the worms can work, as well as a place for you to bury garbage. The best choices are some form of cellulose: newspaper strips, shredded computer paper, leaf mold (from the bottom of a decaying leaf pile), coconut fiber, and wood chips — or a combination of any of these. A handful or two of garden soil, powdered limestone, or rock dust (also called rock powder) provides grit to aid worms in breaking down food particles.



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