Building & Keeping a Worm Bin at Home

worm bin illustrationWith the threat of charging to haul away household kitchen waste in King County, it’s time to get serious about worm bins.  Worm bins are the new compost pile, people. I promise.

Nine out of 10 clients ask me about setting up a system for home composting.  The biggest issue with composting on a small(ish) city lot is that we often don’t have enough ‘browns’ and ‘greens’ to make up a successful hot compost.  And cold compost just takes so long!   The quick fix solution?  A worm bin.  It’s cheap to set up, easy to store outdoors and will pepper your beds with nutrient rich worm casings.  Turn your trash into something useful!

Vermiculture is another great resource for making compost at home in a very small space. Vermiculture uses worms in a worm bin to break down food waste and bedding into compost. Worms produce castings: worm manure, also called vermicompost. These castings are then collected and used on plants and in gardens as lush, nitrogen- dense fertilizer.

A worm bin has the added benefit of being small; it can be stored inside or outside. So it’s an excellent option for apartment and condo dwellers who want to compost at home.

Worms can eat half their weight in food waste every day. If you start off with one pound of worms, count on their handling about a half a pound of kitchen scraps each day. There are a number of options for worm bins, from pricey commercial bins with multiple trays to plastic storage bins or homemade bins. (For instructions on building a worm bin and filling it with proper bedding, see Chapter 7, Do-It-Yourself Garden.) All systems need some method of drain- age, because worms generate liquid waste, and if conditions get too mucky, the worms will not be happy. The worms used in worm bins are not your garden earthworms, but a particular species—commonly called red worms or red wigglers—that would not survive for long in outdoor conditions. You can buy them locally or by mail order, but the cheapest (free!) source is from a gardener who already has a worm bin going.

It is important to note that a new worm bin starts off slowly, so you should add food waste in small amounts at first and monitor how quickly the worms are able to process them. They may ignore foods they don’t like; if so, remove these scraps from the bin so they don’t rot and give off odors. When you add food to the bin, lift some bed- ding and put food scraps underneath. This will help minimize odors. Additionally, when adding scraps you should utilize a different part of the bin than the last time, so the worms have a chance to process the older scraps before more waste is piled over them. Plan to follow a pattern, moving from left to right and then right to left, back and forth through the bin.

Worms can get finicky about what they will or won’t eat. A few finely crushed eggshells provide grit to help them digest, as worms do not have teeth. Do not give the worms proteins, dairy, oil, or oily products like vegetables cooked in oil or fried potato chips. Instead, include only plant-based organic matter like vegetable and fruit scraps. I have seen many a worm ignore citrus peels, but you can try them. Worms also love coffee grounds, and you can include the paper filters. Grains (stale bread, tortillas, and so on) are OK too.

Keep your worms in a temperate location, ranging from 55 ̊F to 75 ̊F; this means you may need to bring an outdoor bin inside during cold winter months.

After a few months, the worm compost will likely appear dark brown, like finely crushed cookie crumbs. This can take up to six months. To harvest your compost and re-bed the bin, move the entire contents of the bin over to one side. On the other side, refill the area with a mound of fresh bedding. Add some new kitchen waste to the new bedding side and wait for the worms to migrate over. This can take anywhere from two weeks to the better part of a month. Worm compost can be used on all potted plants and even indoor plants.

Top-dress your pots with a sprinkling of worm compost every six weeks or so. As worm castings are quite nutrient rich, you want to be sure not to add too much too often or you run the risk of plant burn from overfertilization.

As mentioned earlier, worms also expel liquid as they work to break down your kitchen scraps. You can collect that liquid and add it directly to plants along with the vermicompost. Or add equal parts water to the worm “tea” and spray or water your plants with this solu- tion. This also makes a great gift for any gardeners in your life.