As kids, we thought worms were good for only two things: fishing and daring someone to eat them. Adults, however, can use them to compost indoors.

In traditional composting, a bin is outside, where landscape waste and kitchen scraps decompose to form a nutrient-rich organic matter that can be worked into the garden or top-dressed over the ground. Vermicomposting is the addition of worms to the compost pile to enhance the decomposition. And it can be done indoors.

In traditional composting, the pile needs to be turned over to aerate, boosting the microbial activity with oxygen to avoid the rotten smell of anaerobic decomposition. In vermicomposting, worms do the aeration and accelerate the decomposition.


Not any old worm will do the trick. The common earthworm typically feeds on soil. However, redworms or red wigglers (Lumbricus rubellus) have a taste for kitchen scraps. As they feed, the excrement (called castings) left behind is nutrient-rich material, containing five times as much nitrogen as the surrounding soil.

Redworms survive in temperatures between 40 and 80 degrees. However, you don't need to go digging for them, they can easily be purchased online at www.find

Plan on using 1 pound of worms for every 1 square foot of the bin.


For indoor vermicomposting, a wood or plastic bin can be used. Since redworms tend to be surface feeders, the bin should only be 8 to 12 inches deep. An ideal container would be 2 by 3 feet and 1 foot deep. This helps avoid oversaturation at the bottom, where anaerobic decomposition is likely.

Redworms avoid light, so use an opaque bin that will keep it dark on the inside. Don't snap the lid tight in order to allow air penetration.

Some sources suggest drilling 1/8-inch to 1/4-inch holes in the top and sides to improve aeration. In order to preserve my marriage, I skipped that step. I had a hard enough time convincing my wife the redworms wouldn't open the loose lid and escape.

Good tutorial videos for bin construction can be found at Worm composters also can be purchased ( and are easy to assemble with a spout at the bottom for compost tea, a nutrient-rich, microbial-enhanced water.

Bedding material

Bedding material will substitute for soil. Shredded cardboard, computer paper or newspapers are excellent. Soak the bedding material until saturated, then squeeze the excess moisture out until it's more like a damp sponge. Fluff the material inside the bin until it is about two-thirds full.

Some sources suggest adding a handful of soil or sand because worms have gizzards to help grind up their food. Food sources such as crushed egg shells and coffee grounds also can supply them with the proper grit to keep the gizzards active.


Fruit and vegetable waste is ideal. Citrus should be moderated because of its acidity. Starchy materials, such as potatoes, also should be moderated. Crushed egg shells, coffee and tea (including the filters) are good, too.

Avoid dairy, meat, oils, pet waste and anything that contains chemicals.

Food can be added to the top of the bedding, although it is best buried in pockets around the bin. Start adding food slowly at first. Worms don't feed directly on the scraps but on the microbial soup that forms on them.

A properly active bin should smell earthy. Sour or foul odors indicate anaerobic conditions and that your bin is too wet.


It should take three to four months for the worms to convert all the bedding and scraps into a rich, soil-like compost.

In order to harvest, the compost can be sifted through a 3/16-inch mesh screen to save the worms.

Another method is to expose the compost to light and harvest the top layers as the worms go deeper.

A third method is to push the compost to one side and add fresh bedding and scraps to the other side. In a few days, the worms will migrate to the new food and the compost can be harvested.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, email him at