What is vermicomposting?
Vermicomposting uses worms, usually species adapted to living in decaying organic matter, to break down food scraps and bedding into castings. It differs from ordinary compost in that it relies on worms rather than on heat, and it generally works in a bin kept at moderate temperatures.
These worms are not the same as the earthworms you find in garden soil, which do not thrive in a bin. Ask your extension office or a local supplier where to get worms suited to composting.
Small farms use worm bins for kitchen waste from the household and for farm stand trimmings, since a bin can sit in a shed or basement out of the weather and still work through the year.
What does a worm bin need?
A bin needs a container with ventilation and drainage, bedding such as shredded paper or cardboard kept moist, a starting population of worms and food scraps. The bin should be shaded, away from direct sun and not exposed to freezing or extreme heat.
Many designs work, from a simple lidded tub to a stacked tray system or a larger outdoor bed. Choose the size according to how much food waste you produce and the space you have. Ask your extension office for design plans and cautions.
Check the temperature in the bin occasionally with your hand and a thermometer if you have one. A bin kept in a warm garage may overheat in summer, while an unheated shed may freeze in winter.
- Container with ventilation and drainage
- Moist bedding
- Composting worms
- Shaded, temperate location
What should I feed the worms, and what should I avoid?
Fruit and vegetable scraps, coffee grounds and crushed eggshells are common foods. Add them in small amounts and bury them in the bedding so they do not attract flies. Cut or chop large pieces so worms can work on them quickly.
Avoid meat, fish, dairy, greasy foods and large amounts of citrus or onion, which can cause odors or harm worms. Do not add pet waste, diseased plants or anything treated with chemicals. If you are unsure, leave it out.
Crushed shells add grit that helps worms and may help buffer acidity. Add scraps in a different spot each time and keep a record of what you added so you can trace problems.
How do I keep the bin healthy?
Moisture should feel like a wrung-out sponge. Too wet and the bin smells and worms may try to leave; too dry and worms slow down. Add dry bedding if it is wet and water lightly if it is dry. Feed in proportion to what the worms eat, and do not overfeed.
Temperature matters. Worms prefer moderate conditions and suffer in heat and hard frost. Move the bin or insulate it in cold or hot weather, and check extension advice for your climate.
Add a layer of dry bedding on top after each feeding. It blocks flies, absorbs extra moisture and gives worms a place to retreat.
What problems come up and how do I fix them?
Odor usually means too much food or too much moisture. Fruit flies come from exposed food, so bury scraps and cover the surface with bedding. Worms crawling up the sides may signal poor conditions, such as wet, acidic or overheated bedding.
Ants, mites and other small visitors are common and often harmless in moderation. If a problem persists, reduce feeding, adjust moisture and ask your extension office.
- Smell: reduce food and moisture
- Flies: bury scraps and cover
- Escaping worms: check moisture and heat
- Persistent pests: ask your extension office
How do I harvest and use castings?
Castings are ready when most of the bedding and food has been converted. Several methods exist for separating worms from castings, such as moving finished material to one side of the bin so worms migrate to fresh food. Ask your extension office for methods suited to your bin.
Use castings as a soil amendment or in potting mixes. Do not treat them as a replacement for soil testing. Because their nutrient content varies, rely on your soil test to guide additions.
Do not apply castings in unmeasured heaps. A thin layer or a modest mix is enough, and plants that are sensitive to salts may need extra care, so ask your extension office.
What does it cost, and should a small farm bother?
Costs are modest: a bin, bedding, worms, a place to keep it and your time. A household bin handles a household's scraps, and larger operations need more space and planning. Check local rules if you are considering selling castings or worms, since sales rules are local and vary.
Vermicomposting is a good fit for those with limited space, but it is not a way to deal with large volumes of animal manure or farm waste. For those, ask your extension office about other composting methods.
Key takeaways
- Use composting worms in a ventilated, moist, shaded bin.
- Feed small amounts, bury scraps and avoid meat, dairy and grease.
- Control moisture and temperature to prevent odor and loss of worms.
- Use castings as an amendment alongside soil testing.
Sources and further reading
Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.