Worm bins are designed for composting food wastes using red worms (Eisenia Foetida). Vegetable and fruit scraps from the kitchen are added on a regular basis; the worms eat the food waste and turn it into compost.

What you need

• a container that is wide and shallow 
• red worms
• bedding
• fruit and vegetable scraps from your kitchen

How you do it - Fill the container three-quarters full with moistened bedding. Add the worms. Pull aside some of the bedding, bury the food waste and cover it up.

What happens - During a period of two to three months, the worms and microorganisms eat the food waste and bedding and produce a rich compost.

Worm bins - four steps:
1. The container and the worms
Build a wooden worm bin (use the plans in this brochure), buy a plastic tub with a lid, or use an old trunk or drawer. Wooden containers are absorbent and good insulators. Plastic containers maintain a constant moisture level but may get too wet.

The container should be between 8 and 16 inches deep, with holes drilled in the bottom and sides for aeration and drainage. The bin design in this brochure will accommodate about one pound of red worms (1,000 to 2,000 worms) and process about seven pounds of fruit and vegetable scraps each week. Raise the bin on bricks or wooden blocks for air circulation and to protect from freezing in winter. Place a tray underneath to capture any excess moisture.
Cover the bin to conserve moisture and provide darkness for the worms. Place a sheet of dark plastic on top of the bedding to retard moisture loss and discourage fruit flies.

Worm bins may be located outdoors, or in the basement, shed, garage, balcony or under the kitchen counter. They need to be kept moist, dark and out of hot sun. When temperatures drop below freezing, bins should be moved indoors or be well-insulated.

There are local and mail order suppliers of red worms. Red worms are recommended because they quickly and efficiently process food waste into vermicompost. These worms will probably not survive in your garden. Most suppliers sell red worms by the pound. Availability of worms may fluctuate seasonally. A list of suppliers is available from Metro Recycling Information.

2. The bedding
Suitable bedding materials include shredded newspaper or cardboard, brown leaves, straw, peat moss and/or sawdust. Mix more than one bedding item in the bin to create an environment with spaces for air and to allow easy movement by the worms. Fill the bin three-quarters full with bedding that has been moistened so it is as wet as a wrung out sponge. Add a handful of dirt to provide necessary grit for the worms' digestion. Cover the bedding with a dark sheet of plastic to maintain a constant moisture level and discourage fruit flies. During the course of several months, the worms will eat the bedding. Add more moistened bedding as necessary to maintain the bin at three-quarters full.

3. Food waste
Do feed your worms

• vegetable scraps
• coffee grounds and filters
• tea bags and filters
• limited amounts of old bread (no butter, mayonnaise)
• fruit peels or pulp

Do not feed your worms

• meat
• fish
• dairy products
• greasy or oily foods
• pet wastes

To avoid odor or pest problems, do not compost meats, dairy products, oily foods or grains. When adding food waste to the bin, pull aside some of the bedding and bury the food. Bury successive loads in different locations in the bin.

4. Harvesting your compost and cleaning out the bin
After several months, there should be a marked reduction in the amount of bedding in the bin. Dark, crumbly compost castings will have collected in a layer on the bottom of the bin. It is time to remove some of the finished compost and add new bedding.

The quickest method is to build fresh bedding on one side of the bin and feed the worms on that side only. Wait two weeks until the worms have migrated to that side, then move the bedding from the whole bin to that side. Remove the finished compost from the "worm-free" side of the bin. Use the compost on your house plants, seedlings or for general garden use.

Add new moistened bedding to the empty side of the bin. Next time you add food, put it in the new bedding. The worms will migrate into the new bedding to eat the food.

After several more months, repeat the procedure to remove the finished compost from the other side of the bin.

Common problems

Odor -
To avoid unpleasant odors:

• add only enough food that the worms can eat in a few days
• maintain air spaces in the bedding
• keep bedding moist but not wet
• add only the proper food items

Fruit flies -
To discourage fruit flies:

• bury the food waste in the bedding
• place a dark plastic sheet over the bedding
• put the bin in a location where a few fruit flies will not bother anyone

Too hot or too cold - Excessive heat, above 90 degrees or excessive cold, below freezing, can cause the worms to die. If your worm bin is outdoors, insulate it during the heat of summer and the coldest part of winter with straw, brown leaves or an old blanket thrown over the bin. Moving an outdoor bin into the garage or shed will provide protection during hot or cold spells.

Build your own worm bin

This bin will accommodate one pound of worms and handle the food waste for a family of four. It can be built for about $45. To request a brochure with illustrated directions, call Metro Recycling Information, 234-3000 or send e-mail to mri@metro.dst.or.us

Tools

• Tape measure
• Skill saw or rip hand saw
• Hammer
• Saw horses
• Long straight edge or chalk snap line
• Screwdriver
• Chisel
• Wood glue
• Drill with 1/2" bit

Use eye and ear protection

Materials

• One 1/2" sheet of plywood (treated wood is not recommended)
• One 14-foot utility 2x4
• One 16-foot utility 2x4
• One pound 4d galvanized nails
• 1/4 pound 16d galvanized nails
• One piano hinge with screws
  

Construction of the bin
Measure and cut plywood as indicated in drawing below. To make base, cut the 14-foot 2x4 into five pieces; two 48 inches and three 20 inches long. The remaining 12-inch piece will be used to make the sides. Nail the 2x4s together on edge with two 16d nails at each joint as illustrated in the base frame diagram. Nail the plywood base piece onto the 2x4 frame using the 4d nails.

To build the box, cut three 12-inch pieces from the 16-foot 2x4. Place a 1-foot 2x4 under the end of each side panel so that the 2x4 is flush with the top and side edges of the plywood, and nail the boards into place. Nail the side pieces onto the base frame. To complete the box, nail the ends onto the base and sides. To reinforce the box, place a nail at least every 3 inches wherever plywood and 2x4s meet. Drill 12 holes, 1/2 inch in diameter, through the bottom of the box for drainage.

To build the lid, cut the remainder of the 16-foot 2x4 into two 51 inch lengths and two 27-inch pieces. Cut lap joints in the corners, then glue and nail the frame together. Center the plywood on the 2x4 frame and nail with 4d nails. Lay top on ground with plywood touching ground. Attach hinge onto the top and back using the short screws to the top and the long screws to the back. Center the hinge and make sure the screws go through the plywood to the 2x4s.

Summary

A worm bin is an ecosystem. About eight microorganisms will thrive in your bin with the worms. Together they eat, reproduce and make compost. It is your responsibility to maintain an environment conducive for life. The worms, in turn, will thrive, reproduce and generate an enormous quantity of high-quality compost.