What is vermicomposting?

Vermicomposting, or composting with worms, helps you keep a compact, non-smelly, and fully contained compost bin, even without the benefit of a large space or a backyard.

How do you compost with worms?

Not all worms are alike. The worms that do a stellar job of eating your leftover food scraps and pooping out the world’s best natural fertilizer are called red worms (Eisenia fetida, aka red wigglers). When you compost with worms, you create a happy environment for red worms to do their thing—eat voraciously, turning your food scraps into brown gold.

We think vermicomposting is the best system for the majority of home composters because worms like to eat what we eat, are happy to eat plant trimmings, and can be made comfortable in a wide variety of locations, such as inside the house, in the garage, or on the porch.

It’s the perfect choice for urban dwellers with small spaces and mountain folks worried about attracting animals with outdoor compost bins. It’s also easy to do with our DIY worm compost bin guide!


DIY: How to Make Your Own Worm Compost Bin

While worm bins are available online for anywhere from $50–200, you can make your own bin for a fraction of the cost using two inexpensive plastic storage bins! (Note: If you decide to build your bin out of wood, don’t use treated wood or toxic finishes. Finishes can contaminate your compost.)

To make your own worm compost bin, you will need:

1) Two 14-gallon storage boxes (we use a Rubbermaid® Roughneck® tote). You want to match the size of the bin to the amount of food scraps you generate: Allow 3 square feet of surface area in your bin for every pound of food scraps you generate per day. Also, make sure your bin is at least 10″ deep. Generally, a typical 10-gallon storage box is a good fit for a two-person household. 

You’ll need one box for the food scraps and worms, and another box to catch the drippings, or compost leachate, underneath.

2) One lid. Worms require darkness, so you will want a lid to perfectly cover one of your bins. 

3) A drill. Worms need oxygen, so you will need to drill holes in your lid and in the bottom of one of your boxes. The holes in the bottom of Box 1 will also serve to drain excess moisture. You want five holes for every square foot of feeding surface area inside. A 1/4″ drill bit is a good size. If you’re using a 10-gallon storage box, 12 holes in each will work well. 

4) About 1,000 worms—or 1 lb. Yes, it sounds like a lot, but it’s actually the perfect amount for this compact, food-scrap-heavy bin. 

Setting Up Your Bin

Have your bin ready before the worms arrive. Create a layer of bedding several inches thick using strips of moist newspaper. Mix in a small amount of soil or finished compost for the worms to ingest into their gizzards—they need this to digest their food. Then add a small amount of food scraps and watch them go to work!

Vermicomposting FAQs

Healthy compost smells like soil. If your compost is smelly, that’s a sign that it needs more air. Aerate your compost by regularly turning your pile.

Not overloading the system with too much food at once can also create healthier compost conditions. When you add food scraps, always bury the food by pulling aside some of the bedding, dumping the waste, and then cover it up with the bedding again. Bury successive loads in different locations in the bin.

Worm poop (aka worm castings) makes soil nutrients and beneficial microbes much more readily available to plants than regular compost. It’s the best compost in the world.

Avid gardeners may find themselves vermicomposting everything (including leaves in the fall) because of the wonderful worm castings that can be harvested.

Your worm bin is definitely a potential food source for animals like squirrels and, yes, even bears, if left outdoors. You’ll have to judge for yourself the level of bear activity where you live. If bears aren’t regular inhabitants of your neighborhood, you may be able to do worm composting outside undisturbed year-round in more temperate climates. If the floor of their habitat is just the ground, they can burrow down when their environment gets too hot, cold, or dry. However, if bears are common where you live, keep your worms in a bin and bring it indoors in late summer and fall when bears are loading up on calories for hibernation. This also protects the worms from extreme cold winter temperature.

Squirrels are usually deterred by a well-fitting lid. Raccoons may be the most difficult to deter because they are so dexterous and persistent. If you see tooth marks on your bin or other evidence of a raccoon visit, bring your bin inside for a few weeks.

A small population of fruit flies during spring and summer months is probably inevitable, so the best way to minimize this issue is to keep your bin outside.

If you want to keep it indoors, choose a place where you can tolerate a few flies. You can keep their population in check by avoiding overfeeding the worms, which limits the amount of rotting material available for the flies to lay their eggs on. Fruit flies also prefer a slightly acidic environment, so if you have more flies than you can tolerate, cut back on the amount of citrus, coffee grounds, and other acidic foods in your bin. Or, build your own fruit fly trap.

Spring is a good time to harvest worm castings, but if you have a smaller worm bin, harvest as needed if your bin is getting too full. First, spread a fresh layer of kitchen scraps across the surface and moisten to attract all your worms to the top. Give the worms several days to move up into the fresh food. Then, gently remove the top several inches containing the worms and undigested food. You can place this top layer off to one side on a tarp, out of the sun, until you get down to uniform, completely digested, finished castings. Then dig out the finished castings and gently put the worm/undigested food layer back in the bin. Worm castings are richer than standard compost so you only need a fraction of the amount, but otherwise use the castings as you would standard compost.

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