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How To Start a Home Worm Composting System

updated May 8, 2019
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It all begins with the soil. Worms are the great transformers of landscape through eating and digesting. They can consume a patch of stones and over time turn it into a fertile field. Worms continually pass soil through their intestinal canals, keep anything they can use for food, and then “cast” the rest. With indoor worm composters, these creatures can take your coffee grinds, lettuce scraps and apple cores and turn them into fertilizer castings that your plants will love.

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(Image credit: Apartment Therapy)

What You Need

Small stainless steel bucket with carbon filter
Kitchen scraps, like salad greens, egg shells, and coffee grounds
A minimum of 1,000 red worms
A container, size varies (see instructions)
Newspaper, sawdust, cardboard, or straw, dampened
Contact paper (optional)

Electric drill


Different worm composters will come with instructions and bedding, but here are a few basics for getting started.

1. To start with, keep a small stainless steel bucket with a carbon filter in its lid next to your sink for scraps. The carbon filter is so that no odors escape. Particularly early on, try to pick out vegetables for your worms that are non-acidic, like salad greens rather than onions. Also eggs shells that have been ground up, tea bags, and coffee grounds can go into the mix. Later, when the worms become heartier eaters, you can increase the volume and variety of vegetables and fruit that you feed them, but avoid oily food, clippings from house plants or any animal matter. I also try to only give mine organic produce so that there are no traces of pesticides in their food.

2. Order your worms. You need a minimum of 1,000 red worms to start with, and if you have a large commercially built composter, start with 2,000. It sounds like a lot, but it’s not. They actually reproduce, but will not overpopulate.

On Containers: A reusable plastic storage container works if you have this, but you can also use wood or other non-permeable materials. Just make sure there are air holes so the worms can breathe, and a lid, so they don’t escape. Adjust your container to the size of your apartment. If your kitchen is tiny and this might be tucked under the sink, use a box about 6-8 inches deep, 24 inches long, 6-8 inches wide. For this size order about 10,000 1,000 red worms. If you have a pantry or closet off your kitchen, or even a corner for them, you could use a larger box, or order a larger, layered worm composter, such as the Can O’Worms. For this size order 20,000 2,000 worms. The worms are shipped, but they do just fine.

Here are a few places from which you can order worms:

3. Drill or poke air holes into your plastic container.

4. Add bedding to the container. Pre-purchased composters, such as those you can get from CompostBins or Eco-Outfitter, come with bedding, but if you want to make your own, use newspaper, old cardboard, sawdust, and even pieces of straw. (Some instructions will tell you to use manure, but I avoid this in case the animals were given any de-worming medication.) Dampen this slightly, so that it feels like a wrung sponge.

5. Empty the worms into the tray. They don’t like sunlight, so will quickly dive down into the matter if you leave the lid opened and exposed to light for a few moments. Then cover them with dampened newspaper.

6. Place a few handfuls of your kitchen waste here—if you chop it into smaller pieces it will be easier for the worms to eat. You’ll need to adjust the amount as you get to know them. Start with smaller amounts of scraps, ½-1 cup at a time. If the table scraps rot, remove them from the composter. If the worms are eating them, add more, but as a rule of thumb, you should never have more than a 1/2 inch layer of food scraps across the surface area. Then cover the food with damp newspaper. (It shouldn’t be soaking wet, just damp.) Store your container in a dry, temperate place. 70 degrees is ideal.

Note: Signs that you are overfeeding your worms include black flies in your compost bin. If you find black flies, remove some of the food and in the future give them less. I like to feed my worms smaller amounts at more frequent intervals. Mine are a little fussy and don’t like rotted produce.

7. It should take 3-6 months before you can begin harvesting your castings. You can do this a number of ways, but the least messy is to harvest your castings in a homemade, single level container. Push your worms and vermicompost to one side of the container and lay fresh bedding and food on the other side. The worms will migrate over and then you’ll be able to harvest the composted matter from the other side. After you remove it, add new, fresh bedding. Or, sometimes if I’m feeling lazy, I’ll just root around in the worm bin with a small trowel and pull out castings, and pop them into my houseplants. Sometimes you scoop up a worm or two, but they are good for the plants as well. You can mix the castings in to potting soil and then keep adding it by layering it over the soil in your planters. As you water, the nutrients will drain into the soil.

To fertilize, sprinkle over the soil of your houseplants. If you have a bigger harvest, these can be saved in bags and then mixed with potting soil when starting new plantings. One big advantage to using worm castings is that you really can’t over-fertilize with it they way you can with store-bought fertilizers.

Additional Information:

For more information on composting, check out these resources:

About the Author:

(Image credit: Apartment Therapy)

Maria Finn has written for Saveur, Metropolis, Forbes, The New York Times, ABC.com, and The Los Angeles Times. She is the founder of Prospect & Refuge, a garden-design and installation firm and also writes the weekly newsletter/blog City Dirt, dedicated to adventures in urban gardening. Her newest book, A Little Piece of Earth: How To Grow Your Own Food in Small Spaces, will be released on February 16. She lives on a houseboat in Sausalito, California.

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(Images: Maria Finn. Originally published 2010-02-05)