The Workbench: Worm bin home for a cast of thousands

Here's a win-win weekend project that will help you turn food waste into garden compost using red wiggler worms. Build a wooden worm bin similar to ones used by Anson Biller, manager of Taproot Farm at Sebastopol-based Permaculture Skills Center.

Or modify a plastic storage bin, a system used by Rick Kaye, founder of the Healdsburg-based Compost Club. Both are good choices for people without enough room or sunlight for traditional composters.

Building a wooden worm bin

Tools required:

Electric or battery-powered drill

1/8-inch and half-inch drill bits

1 pound 2-inch-long No. 10 galvanized Phillips-head deck screws, or 8d galvanized nails

Measuring tape, pencil and straight-edge

Handsaw or power saw

Pry-bar or wood chisel to remove pallet slats

Materials:

two 3/4-inch x 5-1/2-inch x 30-inch pallet boards

two 3/4-inch x 5-1/2-inch x 28-1/2-inch pallet boards

Two 30-inch x 30-inch sheets of 1/2-inch or 5/8-inch plywood (many lumber yards can cut to size)

1 sheet 28-1/2-inch x 28-1/2-inch x 1/4-inch galvanized hardware cloth

34-inch x 34-inch weed-block cloth

4 12-inch x 12-inch cinder blocks

Note: Since recycled wood can be brittle, screws minimize wood splitting and maximize holding power.

Assembly: Butt the two 28-1/2-inch boards flush with the ends of the two 30-inch boards (measure the outside dimensions to confirm the 30-inch x 30-inch outside dimension).

Mark a vertical center line about 3/8-inch from the end of the boards to ensure the screws are centered.

Pre-drill two pilot holes using the 1/8-inch drill bit before attaching the screws. Then drill a series of ventilation holes 4 inches apart along the top inch of each side. Attach one 30-inch plywood sheet to the bottom with one screw every 6 inches.

Drill half-inch drainage holes on a 4-inch grid in plywood bottom. Insert a sheet of half-inch galvanized hardware cloth on top of the plywood and line the sides with weed-block cloth to minimize moisture wicking.

Use the second piece of plywood for an easily removable top. Be sure to drill ventilation holes on a 3-inch grid, using the 1/8-inch drill bit. Set box on cinder blocks for ventilation and rodent control.

Bins can be stored in any available nook or cranny out of direct sunlight. Choose a cool location to keep temperatures between 55 and 85 degrees F. Too cold, you will slow the worms' activity. Too hot, you play havoc with their health.

Making a plastic storage container: With a child often serving as a family's chief worm farmer, plastic bins may be easier to handle when full of mature worm-castings. Kaye's design is an ideal "entry level" project.

Materials and tools required:

Two 1-foot by 2-foot plastic boxes, dark colored

Drill

1/4-inch and 1/16-inch drill bits

Four 12-inch x 12-inch cinder blocks

Assembly: The only necessary modification is drilling ventilation holes on the sides and top and drainage holes on the bottom.

Turn both boxes upside down and drill 1/4-inch holes on a 3-inch grid to provide drainage. On each of the four sides, drill a series of 1/16-inch holes spaced about 1-1/2 inches apart.

On just one of the tops, drill about 40 ventilation-holes using the 1/16-inch inch bit. Do not drill holes in the second lid, as it will be used as a drip pan under the bottom box when it is set on cinder blocks.

Stocking Your Worm Bin: Shred newspaper and junk mail into 1-inch strips. (If the paper has colored printing, confirm that the ink is biodegradable soy-based before using.) Soak the paper in water and wring out.

Cover the bottom of the bin with 3 to 4 inches of moist, fluffed shredded paper (a carbon source). Then add organic clippings such as leaf litter and a handful of dirt to help the worms' digestion.

Finally, add kitchen food waste, burying them to minimize bugs and fruit flies. Be sure to rotate your deposit locations. As a rule of thumb, worms consume half their body weight every day, so 1 pound of worms require half-pound of feed daily.

Drop in 1 pound of red wiggler worms. Then cut and place a piece of moistened cardboard to fit over the top of the worm/bedding mix.

The worms cost about $25 per pound and are available from Biller at the Permaculture Skills Center, anson@permacultureartisans.com; Kaye at compostclub@gmail.com, 922-5778; or Sonoma Valley Worm Farm, sonomavalleyworms.com, 996-8561.

Care and feeding of red wigglers: Worms are vegetarians. They prefer breads, grains, cereal, coffee grounds, fruits, tea bags and veggies. They despise all dairy products, fats, meats and oils, as well as onions and garlic.

Once your bottom bin has generated ample worm castings (usually three or four months) stop feeding the worms. It's time to load a new bin with the mix detailed above and set firmly on top of the bottom bin. Caveat: Fill it to the top with soil as worms cannot jump.

In three or four days, most of the worms will have migrated through the holes in search of food. Some will remain below, so give them another three or four weeks before harvesting the castings.

(Tom Wilmer has been a licensed general contractor since 1986. Contact him with questions or suggestions at tomwilmer@aol.com.)