Jock Robie of Gorham is spreading the gospel of worm composting, a topic he’s so passionate about that he maintains 30 worm bins at his own home.

Worm composting, or vermiculture, makes the world a better place in many ways. Most immediately, it keeps food scraps, which are mostly water, out of the solid-waste system – which in Greater Portland is an electricity-producing incinerator, where wet food scraps hinder the process.

Even better, it’s an easy-to-use method of getting rid of your food waste, and it produces a fertilizer that makes your plants grow like crazy.

“The microbes associated with worm castings create chemicals similar to plant-growth hormones and plant growth regulators,” Robie said.

As a result, all parts of a plant fertilized with worm-made compost will grow significantly faster. So if you grow vegetables, you’ll get more produce. While Robie also has outdoor compost bins for leaves garden debris, the worm castings work better than the compost from the bins, he said.

Robie regularly spreads the word about worm composting, and he does it as a community service. He gives 45-minute talks on the topic at places like the Portland Flower Show. He also offers two- to three-hour programs at which he helps people set up with worm-composting bins for free. (The bins would cost about $30 elsewhere.) A chemical engineer who retired from a career in the paper industry, Robie began giving presentations on worm composting in 2011.


Robie recommends using 20-gallon plastic bins – the type often used for storage. Such bins will weigh about 40 pounds each when full of worm compost, he said, about as much weight as most people will want to lift when separating the worms from the castings.

To make a worm box, he creates a grid using wood strapping (small, cheap lumber usually used to attach to studs) at the bottom of the bin, so the leachate from the composting process can drain. On top of the grid he adds a layer of flat, wet newspaper weighing about 2 pounds.

Next he creates the bedding from shredded wet newspaper.

“It needs to be moist because worms breathe through their skin,” he said, and if their skin isn’t moist, the process won’t work.

The worms are red wigglers, much smaller than the earthworms you find in the garden. Each bin gets about a pound of worms, roughly 100 worms, Robie said.

Robie’s red wigglers.

Robie’s red wigglers.

The newspaper has to be fairly loose, both so the worms can move through it and oxygen is available for the composting process. The worms also eat the newspaper, so it will have to be replenished occasionally.


The kitchen scraps are buried underneath the damp newspaper. By burying the food, it is more accessible to the worms and less accessible to fruit flies and house flies.

Next, Robie puts two layers of damp newspaper on top of the bedding and a piece of fly paper over those, in case flying insects are attracted to the bin. Some people who worm compost either microwave or freeze the kitchen scraps before adding them to bins in order to kill any fruit-fly or house-fly eggs or cocoons.

To finish, Robie puts floating row cover on top of everything, which he attaches with a big rubber band, for a tight fit. For people who have cats that might be attracted to the bin, he adds a plastic cover drilled with holes, but the process works better without the plastic, he said.

Feed the worms vegetable scraps, but no meat, fish or dairy. Animal products, Robie warns, will smell bad.

Each compost bin needs 1 to 1.5 pounds of kitchen waste a week, and most families would need four to five bins to handle all their scraps. To fill his own 30 bins, Robie collects waste from nearby stores, coffee shops and restaurants. He advises people to start with one bin to see how it works.

You shouldn’t put in more waste than the worms can eat because those vegetables will just rot, which hinders proper composing. And since the worms eat the newspaper bedding if you don’t add kitchen scraps, you can go away from home for up to six weeks without the worms suffering.


Keep the worm bins between 60 to 77 degrees; the process slows down at lower temperatures. Some people place bins under the kitchen sink and others in the basement (including Robie, whose spouse shares his interest in the compost operation), although if your basement is too cool, it will require a heating pad.

After three to four months, it’s time to clean out the bin – and harvest the worm castings. Robie dumps the bin onto a clean tarp or other piece of plastic and lets it dry out a bit before sifting the product through a No. 4 (quarter-inch mesh) sieve to save the worms and cocoons. That is faster but loses some worms, so he often will use a No. 8 (eighth-inch) mesh for a second screening.

The compost has to dry because “you can’t screen mud,” he said.

Robie uses the end result both as a worm-compost tea and as solid castings. He makes the tea with a quart of castings in four gallons of water, stirring with a paint stirrer. It is easy to use the tea in the vegetable garden, pouring it over the leaf plants and into the ground, but the tea does not keep long.

Dried castings will keep almost indefinitely, he said. The ideal mixture is 20 percent worm castings and 80 percent soil. If you put in as much as 40 percent castings, plant growth is actually slowed, he said.

My own next step is to figure out a good place for the worm bin that Robie has invited me to come over to his place to build.

Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth and can be contacted at 767-2297 or at

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