Vermicomposting: Vermis Aren’t Vermin

June 12, 2010

Get ready with the big “ewwwww!” I’m going to talk about worm composting.  Worm composting is an excellent way to recycle your household organic waste, cut down on the garbage going to landfills, and inexpensively create a fantastic garden fertilizer. Good eco-karma points — and it’s easy.

Worm compost is made in a container filled with moistened “bedding” and red worms. You add your food waste, and the worms and microorganisms will convert the entire contents into rich compost. Here’s what you need to get started:


A Worm Bin: There are websites that sell ready-made worm bins via mail order. My worm bins are simply opaque Rubbermaid® plastic tubs with lids, with holes drilled in the sides for drainage and ventilation.

The “rule of thumb” is to create 2 square feet of surface area per person per week, which is about 1 lb of scraps per week.  Create a “bed” for the worms with moistened 1” black and white newspaper strips. Keep the bin in a shady, protected spot, so the worms don’t get too hot in the summer or freeze in the winter.

Worms: You need to use red worms or “red wrigglers.” Standard garden worms don’t work, so leave them digging away in your garden. I purchase my red worms locally in Santa Cruz, and there are local suppliers around the Bay Area, as well as mail order suppliers. Contrarily, the red worms will not do well outside of their bin, so there is no danger of introducing a non-native species to your garden.

Worm Food: Feed your worms fruits, vegetables, bread, grains, coffee grounds and filters, tea bags, eggshells, you name it. Unlike some compost heaps, there is little odor. Just don’t put meat or dairy-based items in your worm bin as it can start to smell bad and attract scavengers.  And don’t add grass or other yard clippings, as the compost can get too hot and cook your worms. Put a layer of shredded paper over each food addition.

Harvesting Your Compost: In as soon as 3 months, you can start using your compost. At first, I dumped my bin out onto paper and then put the worms and newer scraps back into the bin, saving the dark worm castings for the garden.  After I outpaced the worms, I started a second bin and now alternate between the two, letting the worms complete their thing in the first bin, while I start the process again with a new set of worms in a second bin.

For use in the garden, many people steep a worm casting “tea,” and water with it. I just spread a 1/2” layer of the compost at the base of my plants and water it in.   For additional information on worm composting and resources, check the California government site at and/or your own county’s Waste Management website.