Unlike other compost bins, the Earthmaker Aerobic Composter, retailing for around $200 and up in 2010, can be used continuously without needing an off-cycle for the compost to mature. It resembles a 55-gallon drum with indents indicating three separate chambers for mixing, digesting and maturing. Compost bins may save money for those who pay user fees based on volume of household waste, and the compost they produce creates a valuable soil amendment for home gardens.
Consumer House and Garden found the Earthmaker the least strenuous type of compost bin, given its use of a push-pull tool instead of a pitchfork for mixing materials. A study by the U.K.-based HDRA (Henry Doubleday Research Association), now called Garden Organic, found that the Earthmaker provided twice as much fully decomposed material (38 percent) than control bins (15 percent), and a much higher proportion (63 vs. 30 percent) of ready-to-use material. The Earthmaker also offers advantages to open piles, in that animals and rodents cannot get into the rotting organic material.
The Earthmaker, manufactured in New Zealand, stands 47 inches high and has a 123-gallon capacity, producing about 10 gallons of finished compost per month.
The Earthmaker can be sited conveniently to your kitchen and should be shaded from the hot midday sun, which can soften the plastic. Level a site about a yard in diameter. The manufacturer recommends constructing a flat base of paving stones or bricks or timber.
Load the top of the Earthmaker with a 1:5 ratio of kitchen scraps to garden waste. Add grass cuttings, leaves and tree trimmings, using a shredder or mower to mince up larger pieces. Add kitchen scraps, vacuum cleaner dust and clothes dryer lint. Fill the top chamber, adding more material as it becomes available. Mix and stir the material in the top chamber weekly or every two to three weeks. Every month, remove the pull-out panel. Gently push the top material down into the middle chamber and the middle-chamber material to the bottom area.
Large amounts of grass clippings can make the mix slimy. Layer grass over kitchen waste to avoid smells and flies. If an odor develops, fold and stir materials in the top chamber to add air. Avoid adding pet waste, ashes or lime to the Earthmaker. Chop up large branches or long twigs or shred garden waste to avoid blockages in the apparatus.
The first batch of mature compost will be ready in three to four months. The manufacturer notes that you can speed this process by adding sugar to the mix, stirring more often or having a 2:1 ratio of carbon or brown materials (dry leaves, sawdust, wood chips) to nitrogen or green materials (wet items such as food scraps and grass clippings).
The significantly different design of the Earthmaker leads to ease of use and produced more than twice as much good quality compost over a 26-week period, according to the study by Garden Organic.