Worm Composting

Worm composting can be a wonderful solution for reducing household waste in places where a backyard compost bin may not be practical: An apartment, a school classroom or an office building. Worm bins are quite small and don't require contact with the soil, which means they can be kept inside or on a patio.

With the proper care and attention, the worms will thrive and help you reduce your waste while making a great fertilizer for your plants.

There are many types of worm bin systems available for purchase or you can build your own.

Building the Bin

An easy and inexpensive option for a home-made worm bin involves using Rubbermaid totes. They come in a variety of shapes and sizes and last a long time.

Generally each square foot of surface area will support 1lb of worms, which will eat half their weight every day. A 53 L Bin (about 2 square feet of surface area) will support 2lbs of worms which will each 1lb of food a day (7lbs a week). A shallow bin is better than a deep bin.

An opaque bin will work best as worms don't like the light. Buy two of the same size bin so you can nest them together to create a sealed drip tray (See Diagram below).

Drill holes in the bottom of the top bin so that any liquid can drain into the second bin. This can be emptied once a month or so. You'll only need one lid. Drill holes in the lid for air circulation. Holes should be about 1/2cm in diameter.

Prepping the Bin

The bin requires a few things before it is ready for the worms:

• First the worms require some bedding. Ripped-up newspaper works best for indoor bins. Bedding in outdoor bins can include leaves, straw, etc.
• Next, you must moisten the bedding. Aim for the moisture level of a damp, wrung-out sponge. All the newspaper should be moist, but it should not be dripping.
• Next, as the worms don't have teeth, they require some sand to digest their food. Add a handful of sand and mix it into the bedding.

Now you're ready for the worms!

Worms:

You need red wiggler worms. They are a special type of worm that likes to live right in their food and will do well in a bin. Dig your own from a friends compost bin or your local stable's manure pile. (Do not get worms from the soil - they're not the right type of worms). You'll need about 1/2 lb to start (and they will reproduce to fill the bin).

You can purchase worms from the following companies:

• Transform Compost
• Earthworks Composting Supplies
• Compost Worms
  
  

Feeding the Worms

Worms bins work best if fed once a week, so save up your food scraps in a container on your counter (or in your fridge during warmer months) rather than putting them in the bin every day.

As the worms can take awhile to eat the food scraps you put in the bin, it's best to add the scraps to a different location in the bin each week. Consider using a popsicle stick to keep track of the last location you fed and working your way around the bin in a clockwise fashion. Add food scraps by pulling aside some of the bedding, dumping in the food and then covering the scraps with the bedding.

Ongoing Maintenance

• Check moisture levels often. The bedding should be moist as a damp wrung-out sponge, but not dripping. If the bin is too wet, simply add more dry bedding
• A gentle stir once a month or so can also help keep the bin from going anaerobic and stinky.
• Empty the drainage bin every month or so. Dilute it and use it to water your plants.

Harvesting

It's best to harvest the bin before it gets full and when there is little or no original bedding visible. Usually between 3 - 6 months after starting or harvesting.

No-fuss Method

Push everything over to one side of the bin and add new bedding to the the empty side (see picture to right). By only feeding the new side, you'll encourage the worms to move out of the finished compost, allowing you to scoop it out as needed (can take about 1 month).

Some-fuss Method

Remove and set aside the top unfinished bedding. Shine a light on the finished compost. This will encourage the worms to move deeper into the bin, allowing you to skim off the top layer. Repeat as many times as necessary to remove finished compost. Replace the top bedding and feed as normal.

Most-fuss Method

Dump the bin out on to a tarp and manually separate the worms from the finished compost. Remember to place the small, lemon-shaped worm cocoons back in the bin. Create small compost piles out in the sunshine to encourage the worms to move to the bottom of the piles and allow you to scrape off the top of the piles.

Tips

• Only open the bin when necessary. It's best to disturb the worms as little as possible.
• Keep the bin somewhere convenient to use, out of the hot sun or heavy rain.
• Avoid placing the bin in an area with lots of vibrations (such as on top of your washer or dryer).
• If you are keeping your worm bin indoors, stick to newspaper as a bedding material as you never know what other critters you're bringing into your home if you use leaves/straw etc.
• Maintain a good thick layer (4-6") of ripped-up newspaper on the top of the bin. The worms will eat the bedding so you'll have to add more every few weeks. Adding this dry bedding will also help you maintain correct moisture levels. This will minimize the chance that you get fruit flies or fungas gnats and also ensure that your bin stays aerobic.
• Worms prefer warmer temperatures (13 - 25*C). If temperatures drop below 4*C, ensure your bin is insulated or move it indoors.
• Make sure you bury all food scraps below the newspaper.
• If you develop problems (hopefully not!) don't get discouraged - there is always a solution. Check out the resources below for help.

Resources:

• Appelhof, Mary. Worms eat my Garbage: How to set up and maintain a worm composting system. Kalamazoo, Michigan: Flowerfield Enterprises, LLC, 1997.
• Metro Vancouver. Here's the Dirt: Worm Composting. Vancouver, BC.
• City Farmer Webpage: Composting with Red Wiggler Worms.
• Compost Hotline: 604-736-2250.