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worm bin compost by mckaysavage on Flickr

Earlier this spring, I wrote about how to start a compost pile in your backyard. Though composting is a relatively simple solution for those who want to create nutrient-rich compost for their garden and recycle food waste, not everyone has a backyard. It's not so easy to create a compost pile on an apartment balcony, and I'm guessing the downstairs neighbors might complain.

City dwellers and those who want to compost year-round can still compost food items, however. You just need some little critters to help the process along. I'm talking about composting with worms.

Worms? Really?

When you provide worms with an appropriate home, they'll work their way through your food scraps and create a dark, rich, moist material that your garden will love. I'll talk more about what types of worms to use and how to build a home for them after the break.

Examples of worm bins(click thumbnails to view gallery)

Multi-bin compost systemWorm bin on a garden patioLooking for wormsTiny worm mansionComposting in an old tire

There are two kinds of worms you can use to compost your food scraps. Red wigglers (also called brandling or manure worms) are popular, but you can also use Lumbricus rubellus, or red earthworms. Note that earthworms typically found in soil are not appropriate for worm composting, and will likely die in your bin.

If you have a friend with a worm composting bin, you may be able to take their extra worms off their hands. Or, you could visit a local farmer and dig through their manure pile. If that sounds like as much fun to you as it does to me, you can also order them online through stores like this one, this one, or this one.

Before we get ahead of ourselves and order our little wigglers, however, let's discuss how to create a home for them.

Bin Sweet Bin

In the book Worms Eat My Garbage, Mary Appelhof recommends that you weigh your food scraps for one week before building your bin. In general, you'll need one square foot of surface area in your bin for every pound of food you'll add to it.

Worms aren't picky when it comes to aesthetics. There are some beautiful worm bins for sale out there, but you can also use materials you have in your home. Build your own bin out of wood, recycle an old dresser drawer or trunk, or use a plastic storage tub. (Note that plastic bins tend to be more "wet" than wood bins.) You can even make a compost bin out of old tires. Instructables has some quick, $5 worm bins as well.

Worms need air like you and me, so be sure your bin is well ventilated. Depending on the size of your bin, you'll need to drill 12-20 holes (1/4 to 1/2 inch) in the bottom of your bin for drainage and aeration. Your worms will also appreciate air holes on the sides of your bin, which you can make with a drill or, in the case of a plastic bin, an ice pick.

Elevate your bin on bricks or blocks so that any water can drain out (otherwise, your worms could drown). Use a tray to catch this nutrient-rich liquid and feed it to your garden plants.

Happy worms are busy worms

Fill your bin 3/4 full with bedding. What makes good worm bedding? Shredded newspaper is probably the most popular option, though others include dry and shredded fall leaves, dead plants, and cardboard.

Wet the bedding
(this is important) and then wring out the excess water so that the material is about as wet as a wrung out sponge. Then lift it to create air spaces. Toss in a handful of soil or sand, which worms will use as grit to aid in digestion. A little leaf litter is a fine addition as well.

Add your wigglers to their bedding. You can also place a piece of damp cardboard cut to fit your bin on top of the bedding and worms. Worms love to chomp on cardboard!

Finally, your bin needs a cover. If you're using a plastic tub, the lid that came with it will do (remember your air holes on the top, bottom, and sides!). Outdoor bins need a solid cover to keep out unwanted pests, but indoor bins can be covered with a piece of burlap or dark plastic. The cover serves to keep your bin dark and moist.


When trying to decide how many worms you need, go back to that number you got when you measured your food waste. You'll want a worm to food 2:1 ratio. For instance, if you have one pound of food waste per day, you'll want to start with about two pounds of worms.

Feed your worms slowly in the beginning. Too much food will lead to your bin filling up, odor, and possibly, pests. Bury your food scraps under the cardboard, in different areas of your bin. Check each day to make sure that the bedding is moist and add small amounts of water as necessary.

Your worms will eat a vegetarian diet. Feed them fruit and vegetable scraps (except citrus), tea bags, coffee grounds, stale bread, and for a special treat, egg shells. DO NOT feed them meat, dairy, grease, oil, or pet waste.

Harvesting your compost

After about two and a half months, you'll notice that the bedding is almost gone and in its place is a dark, rich material. These are called worm castings, or less poetically, worm manure. This means it's time to harvest the compost and provide the worms with new bedding so that they have a place to live and don't go hungry. Worms can't eat their castings, because they are poisonous to them.

There are two ways to do this. One will have your bin reset and ready to go in only matter of an hour or so, but requires a little work on your part. The other is less labor-intensive, but takes a little longer. If you have kids, the first option is a great opportunity for you to teach them about worms.

Carefully dump the contents of the bin onto a large piece of plastic outside. Set your kids or someone else who isn't squeamish about picking up wigglers to the task of picking the worms gently out of the pile while you prepare new bedding for the bin.

If you're using this time as an science lesson, tell your worm hunters to look for the tiny worm cocoons, which contain baby worms. Make sure they make their way back into your compost bin too! Return the worms to their happy home and use the compost on your garden or flower beds.

If you're the more patient type, you can also move all of the worms and compost to one side of your bin. Fill the other side with fresh bedding and start burying your food scraps on that side. Eventually, the worms will all move to that side of the bin, and you can scoop out the (mostly) worm-free compost to use as you like. There's another method that's similar to this one that utilizes an onion bag.

Some helpful tips

  • Worm bins can be placed anywhere -- pantry, kitchen, patio, basement, yard, etc. Keep in mind that worms are happiest when temperatures are between 40 and 80 degrees Fahrenheit. If keeping them outside, pick a shady spot that's protected from rain, and bring them in if the weather is going to turn cold.
  • If your bin stinks, it's because there's too much food for your worms to "process" in a timely manner. Stop adding food until the worms take care of what is already in the bin, then gently fluff the bedding to let more air into the container.
  • If your worms are crawling out of their bedding and up toward the top of their container, it means that something in their bin is making them unhappy. Be sure you aren't adding citrus or other foods that might aggravate them, or that your bedding isn't too wet or too dry.
  • Fruit flies are common worm bin pests. Though they won't hurt the worms, they can certainly get annoying. Prevent fruit flies by burying your food scraps well and by reducing the amount of fruit you put in your bin. If your bin is outside, placing it near a few spiderwebs will also help reduce the problem.
  • You can control the population of your worm bin by adjusting your feeding schedule. Feeding less frequently will result in a lower worm population, while feeding more often (but not over feeding) will mean more worms and more castings (and possibly, more worm bins if your population gets too big!)
  • Though the bedding needs to be moist, it's a common problem among new worm bin owners to drown the worms. Be sure to drill plenty of drainage holes and keep a very close eye on the wetness of your worm's bedding.
  • As always when dealing with live creatures, keep in mind that you've taken them out of their natural habitat and into your care. Though composting with worms isn't difficult, it does require a degree of responsibility and commitment.

Though they aren't all appropriate for feeding worms, if you have a conventional compost pile, Anna recently shared 163 things you can add to your heap. And if creepy crawlies aren't your thing, Francesca can teach you how to build a backyard compost pile (minus the red wigglers) out of shipping pallets.

Happy composting!



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