A worm bin that fits under the sink

About this photo

1It has to be the right worm

Red wigglers (Eisenia fetida), not garden earthworms, are the species used — they burrow shallow and horizontal rather than deep, tolerate crowding, and reproduce fast: a mature worm lays a cocoon of several babies roughly every 7 to 10 days once it reaches maturity around 90 days old.

2Building the bin

A plastic or wood bin about 2 feet by 3 feet and a foot deep works well, drilled with small drainage holes on the bottom and ventilation holes near the top, raised on bricks over a tray to catch drips. It has to stay dark — no clear plastic — and the ideal temperature range is 55–77°F, with 65–70°F best; keep it away from a dishwasher or washing machine, since the vibration bothers the worms.

3What goes in

Bedding is shredded newspaper, cardboard or fallen leaves, dampened to a wrung-sponge feel with a handful of garden soil mixed in for grit. Feed almost any plant-based kitchen scrap — vegetable peels, coffee grounds, tea bags, bread — but skip onion, garlic, citrus and anything with meat, dairy, oil or heavy salt, which the worms can't process well. A couple of tablespoons of crushed eggshell once a week keeps the bedding's pH in a safe range.

4Why it's slower, and why that's fine

A backyard hot compost pile finishes in six to eight weeks under good conditions; a worm bin takes up to six months, since it never heats up and relies on the worms and microorganisms instead of bacterial heat. The trade is real: no turning, no smell, no outdoor space needed, and the finished worm castings carry up to 4% more nitrogen than conventional hot compost.

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