How to Compost Indoors

May 31, 2011 View all articles in Home


Our article 9 Steps to Backyard Composting tells you how to turn your kitchen and yard waste into nutrient-rich fertilizer that improves soil texture and keeps weeds from growing; increases air and water absorption in the soil; and can be used as mulch in the lawn or garden, or as potting soil for houseplants. In addition to helping you grow a better garden, composting also saves landfill space. But what about apartment dwellers or those without adequate yard space? And what about those who want to compost even when it's too cold to do so outdoors? There are actually a couple different indoor composting methods available for those who are short on space, as well as for those who want to compost year-round.


One way is to purchase an electric Naturemill composter that mixes, heats, and aerates on its own so that all you have to do is add waste items and remove compost fertilizer two weeks later. This mechanized composting bin uses about the same energy over the course of a month as a typical nightlight (5 kwh, or $0.50) and can reduce household trash amounts enough to qualify for a discounted collection rate.


The second method is known as vermiculture, or vermicomposting. The key to this type of indoor composting is, well, worms and their manure (known as castings). Worms eat the bacteria and fungi that grows along with the food waste, and turn it into compost. This type of composting is helpful for improving root structure, plant growth, and the blooming of new flowers. It's also the favored method of classroom teachers who want to instruct students about decomposition. But because it's slightly more complicated than the method described above, we're including some detailed instructions give you a clearer picture of the process.

Worm Composting Container

  • Purchase a plastic storage container that measures approximately 24 inches by 16 inches by 10 inches (use the amount of food waste your family produces per week as a size guide) so that it fits conveniently below your sink or in a cupboard.
  • Build a simple wooden box of the same measurements yourself.
  • Whether plastic or wood, you'll need to drill holes in the lid, the tops of the sides, and the bottom for air circulation and drainage. Elevating the container by placing it on bricks will also help the air circulation. And finally, you'll need to place a tray beneath the compost container to collect any excess liquid.

Worm Composting Bedding

  • Shredded newspaper (made with nontoxic, vegetable-based ink), sawdust, shredded cardboard, shredded leaves, dried grass clippings, loam, dryer lint, broken-down egg cartons, and black topsoil all make excellent bedding material.
  • You may want to line the container with nylon net in order to keep the smaller worms inside.
  • Fill the container with about a foot of damp bedding; maintaining the right moisture level is key, but it isn't as difficult once you begin feeding the worms regularly.
  • Varying the bedding material will provide the worms with more nutrients and they will produce richer compost as a result.
  • Keep a bucket of soil at hand so you can easily add a scoopful or two to the compost each time you feed the worms, as this will aid their digestion.

The Worms

  • Red worms (also known as red wigglers, brandling, or manure worms) thrive on organic material and can eat up to their own body weight in food scraps every day.
  • Red worms are often sold as fishing bait, but your local garden center or community garden should be able to help you locate some.
  • Plan on using a half-pound of red worms for each cubic foot of the container (depending on their size, a half-pound equals about 500 worms).
  • Make sure you protect the worms from hot sun, heavy rain, and extreme cold. They're happiest at room temperature and can be kept in a basement, shed, garage, kitchen, or closet.

Feeding the Worms

  • You can purchase a metal, ceramic, or stainless steal compost pail to collect kitchen food scraps, or you can repurpose ice cream tubs or similar food containers that would just be thrown away otherwise.
  • Consult our “9 Steps to Backyard Composting” article for a list of safe and unsafe composting materials.
  • As a rule, red worms like tea bags, coffee grounds and filters, vegetable and fruit scraps, bread, rice, and pasta.
  • Meat scraps, bones, dairy products, garlic, and potato peelings will attract insects and cause odors, and should not be collected.
  • When your collection pail is full, chop the food waste up a bit and feed it to the worms by pulling the bedding material aside, burying the food waste underneath, and covering it with more bedding material.
  • Adding some wood ash or crushed eggshell each time you feed the worms will keep the bedding from becoming too acidic. Alternatively, if your compost mixture becomes too alkaline, simply add coffee grounds to increase its acidity.

Harvesting the Compost

  • Your worms will have turned the bedding and food waste into rich, black soil in about 4 to 6 months.
  • When you're ready to harvest your compost, use the “migration” method:
    • Move the compost material to one side of the container
    • Put fresh bedding on the other side
    • Add food to the side with fresh bedding
    • In a few weeks, all the worms will move to that side, enabling you to remove the mature compost.


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