Compost Tumblers

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Story and photos by Brook Elliott

You've seen the ads: "Now you can have dark, rich compost in just a few weeks!" What an appealing message. Whether you grow flowers, vegetables, herbs or houseplants, compost is "black gold" in the garden. We never have enough of it, and can't make it fast enough. Compost tumblers, the ads say, can give us a steady supply every couple of weeks. Designed so you can crank, turn or roll the container to turn and aerate the compost, tumblers come in several sizes.

Before you run out and buy one, however, be aware that those headlines are advertising hyperbole at best. In our tests, tumblers did not produce finished compost any faster than a well-managed compost bin or open pile.

To be sure, the ingredients appear to be composting faster because you are likely to turn the contents more often in a tumbler, thus introducing air—one of the four vital ingredients (the others being nitrogen, carbon and water)—that is necessary to turn vegetable matter into compost. But if you build an open pile the same size as a tumbler's capacity, use the same ingredients in both and turn the open pile whenever you rotate the tumbler, they will produce compost in the same general time frame. So, why should you buy a compost tumbler?

Last summer we conducted a field test of various compost tumblers versus open compost piles. Although most of us at MOTHER use cold composting methods (substituting time for the work of maintaining a hot pile), we ran a hot pile as a control.

Under our environmental conditions, both the open (hot) pile control and the tumblers yielded rich, finished compost in about 10 weeks—a far ay from the 14 days some of the manufacturers claim. The tumblers were certainly easier to use than turning an open pile with a pitchfork, but they did not appreciably increase the speed of production when compared to a properly managed open pile. Ease of turning is probably the main benefit tumblers offer, but as you will see below, some are easier to turn than others.

Although the decomposition time is not increased, compost tumblers do have advantages in addition to ease of turning. By and large, they are clean, neat, unobtrusive, pest-resistant and odor-free. Because of this, tumblers often can be used in urban and suburban areas, where local laws or restrictive covenants may prohibit open compost piles.

One pleasant surprise during the testing, in what turned out to be a drought year, was that the enclosed tumblers retained moisture better than the open pile, which had to be watered frequently.