Indoor Composting Systems

Kitchen scraps account for 24 percent of Americans’ trash—and almost all of those scraps go into landfills. That’s a shame, because organic waste like banana peels and coffee grounds can be turned into nutrient-rich fertilizer through composting. A few forward-thinking cities (like San Francisco) have programs to pick up your food waste and do the composting for you. The rest of the country has to do it itself. For urban dwellers without the backyard space to create a compost heap, a handful of companies offer small kitchen systems that claim to be easy to use, clean, and odor-free.

CHOW tested the three most popular indoor composting systems with three months’ worth of our test kitchen’s scraps—everything from orange peels to cake batter. Our results are below, with the systems ranked from best to worst.

NatureMill Pro System

The System

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Compost in Process

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The Final Product

The Final Product

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NatureMill Pro

$399

HOW IT WORKS: Waste (along with the sawdust pellets included with the system and baking soda you must add to reduce acidity) is electrically heated in the top of a two-tiered chamber. The machine also mixes, moisturizes, and aerates the food scraps. After the scraps have been thoroughly mixed, the upper chamber automatically opens at the bottom, like a trap door, depositing the waste into the lower chamber, where it breaks down further. After 10 to 14 days, a red light goes on, indicating that the compost is ready to be used. The system also lets you know when there’s a jam and when you need to wait before adding new waste to the upper chamber.

PROS: Odors are minimal (the system produces a natural, subtle scent, like mushrooms or a forest after a storm, and at times a faint dark-chocolate aroma). The NatureMill’s also fast: On average, it can run through about 10 to 15 pounds of food waste per week, producing 1 to 2 pounds of compost. It fits easily in most kitchen cupboards or under the sink, and comes in colors like mint green and red. Because it’s temperature-controlled, it works the same regardless of climate or time of day.

CONS: It’s much pricier than the other systems we tested. Hard items like apple cores and corncobs jammed the system. Long, stringy items like corn husks and kale got tangled in the mixing arms—we had to either cut them up or avoid them. It runs on electricity, though it requires less than even Energy Star–certified appliances.

THE UPSHOT: We plan to keep this, our favorite system, in the test kitchen.

Happy Farmer Kitchen Composter with Bokashi

The System

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Compost in Process

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The Final Product

The Final Product

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Happy Farmer Kitchen Composter with Bokashi

$65.99 for both

HOW IT WORKS: About the size of an office wastebasket, the Happy Farmer kit comes with bokashi, a brown powder that looks like sawdust and is essentially fermented wheat bran. You fill the bin with kitchen scraps and layer them with bokashi, then let the whole thing sit with the lid closed for two weeks. When you open it up you find not soil, but rotted, fermented food that remains physically intact, but that can be added to your garden to increase the soil’s nutrient content.

PROS: The Happy Farmer is small and easy to use. Just open, add food, add bokashi, close, and repeat. You don’t need to cut waste into small scraps first (despite what the website says), the way you do with some other systems.

CONS: The system’s smell, when opened, was described by CHOW’s staff photographer as “rotting corpse.” The end product is unappealing—white, moldy, and resembling moist cotton candy and dryer lint tangled with chunks of decomposing food—which isn’t as easy to approach as dirt. During the two weeks our bin was closed and working, we threw out a lot of food. You’d need a few bins in rotation to be able to compost all of your kitchen scraps.

THE UPSHOT: Too stinky, and not ideal as a kitchen composting system.

Can-O-Worms Worm Composte

The System

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The Final Product

The Final Product

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Can-O-Worms Worm Composter with Two Pounds of Red Worms

$169.85 for both

HOW IT WORKS: The system consists of three stackable plastic rings, two feet across and two feet high when stacked, with a base and a lid. We also bought a two-pound box of red worms from the same company that sells the composter, though you could buy your worms from a garden supply store.

To the lowest ring, you add the red worms and a mixture of one cup of soil and cardboard (the latter is included with the system). Food waste goes on top of the middle ring. The top ring is left empty.

Once the bottom ring fills up with vermicompost (worm manure), the worms crawl up to the next ring through small holes. The bottom ring can then be removed and the vermicompost collected to use as fertilizer. The now-empty ring can then be placed on the top of the system and the process repeated.

PROS: In theory, worm compost systems are the most cost efficient—worms eat their body weight in food daily, have a life span of 15 years, and can double in population every few months. Vermicompost is an ideal fertilizer, with a neutral soil pH (measure of soil acidity) of 7, the optimal pH level for food-producing crops.

CONS: You can’t put any animal products in this composter. If you’re as squeamish as we found we were, you will not like having to deal with 2,000-plus live worms. The critters are also, it turns out, rather high maintenance: They’re extremely sensitive to light and heat (we lost some to a week-long heat wave). They are finicky eaters: Ours refused to eat bananas and dandelion greens, for example. The system is big and heavy (it took two people to move it when full), attracted fruit flies, and smelled like a city dump. Additionally, whenever the lid was opened, a few worms would crawl up the sides of the container, fall off, and creep into the depths of the kitchen. Ugh.

THE UPSHOT: The Can-O-Worms system did produce the best compost material, but it is the most malodorous and hard-to-use indoor composting system we tried.

Michele Foley is a former associate editor at CHOW.