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.