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Composting with Worms

For millions of years, worms have been hard at work breaking down organic materials and returning nutrients to the soil. Worm composting (also known as vermiculture) is one kind of composting that can be done indoors, and is especially great for kids and in classrooms. A worm bin can provide many valuable, exciting, and experimental opportunities for children.

Vermiculture is a supplement to a compost pile, not a replacement for one. It’s a great option for apartment dwellers and others who don’t have space for a full-fledged compost bin. Worm castings are a fantastic fertilizer for houseplants, so it’s well worth keeping both a worm bin and a compost bin.

Worm bins are best kept indoors. Worms thrive in temperatures between 50 and 75 degrees Fahrenheit, and those conditions are usually found in the cool parts of a house instead of outdoors. During hot summers, worms dig down deep to keep cool. They can’t do that in a worm bin, which will heat up to ambient summer temperatures. In winter, freezing cold will kill them, too.  Just remember that when temperatures are extreme, worms are unhappy.

How To Set Up Your Worm Bin

You can purchase fancy bins online, but all you really need to make a worm bin is a rectangular plastic container and a drill.  For the simplest bin, just drill 1/4″ or smaller holes around the entire perimeter of the top of the bin. If the bin has a lid, drill multiple holes in it as well. These provide ventilation. If you are using just one bin, do not put any holes in the bottom, but you’ll need to make sure the bin doesn’t become too wet.

To make a better and only slightly fancier bin, check out the great page and illustrations on the Washington State University website for building, setting up and maintaining a Cheap and Easy Worm Bin.

Once you’ve built your bin, it’s time to order the inhabitants. Regular earthworms are not well suited to worm bins. You’ll have much better success by ordering red wrigglers from a local source:

Wormpost Vermont (this site also has lots of other info about vermicompost and setting up your worm bin)


What to Feed Your Worms

Though worms can eat most organic material, certain foods are better for worm bins:

  • Fruit and vegetable scraps
  • Eggshells
  • Tea bags
  • Coffee grounds and filters

Do NOT include meats, oils, cooked foods and dairy products. They take longer to break down than fruits and vegetables, produce strong odors, and can attract pests.

A few tips to keep in mind:

  • Worms like a varied diet. Generally speaking, the more vegetable matter, the better the worm bin.
  • Conditions in the bin may become too acidic if citrus materials constitute a majority of the foods you give your worms. Worms prefer to have their food cut into small pieces.
  • Some people have also observed that decomposing onions and broccoli tend to produce strong odors.


If you take care of your worms and create a favorable environment for them, they will work tirelessly to eat your “garbage” and produce compost. As time progresses, you will notice less and less bedding and more and more worm castings — compost — in your bin. After 3-5 months, when your bin is filled with compost (and very little bedding), it is time to harvest the castings.

To prepare for harvesting, don’t add food to the bin for two weeks. Try one of two methods for harvesting:


Push all of the contents in your worm bin to one half of the bin, removing any large pieces of non-decomposed food or newspaper. Put fresh bedding and food scraps in empty side of bin. Continue burying food scraps only in freshly bedded half.

Over the next 2-3 weeks, the worms will move over to the new side (where the food is), conveniently leaving their compost behind in one section. When this has happened, remove the compost and replace it with fresh bedding. To facilitate worm migration, cover only the new side of the bin, causing the old side to dry out and encouraging the worms to leave the old side.


Dump the entire contents of the worm bin onto a sheet of plastic or paper. Make several individual cone-shaped piles. Each pile will contain worms, compost and non-decomposed food and bedding. As the piles are exposed to light, the worms will migrate towards the bottom of the pile. Remove the top layer of compost from the pile, separating out pieces of non-decomposed food and newspaper. After removing the top layer, let the pile sit under the light for 2-3 minutes as the worms continue migrating downward. Then remove the next layer of compost. Repeat this process until all of the worms are left at the bottom of the pile. Collect the worms and put them back in their bin with fresh bedding.

Using Worm Compost

Mix your worm compost with potting soil for added nitrogen. Unlike chemical fertilizers, worm castings provide a slow release of water-soluble nutrients. Castings contain 5x the available nitrogen, 7x the available potash and 1.5x more calcium than that found in  good top soil. Experiment with planting seeds in containers with and without castings and you’ll observe significant differences!