Food waste is composted by a wide range of technologies, from low-tech windrows that require only a front-end-loader to mix and turn piles, to medium-tech aerated static piles and windrow turning machines, to high-tech in-vessel containers with aeration and agitation systems. The guiding principle of higher tech equipment design is to maximize the presentation of surface area of the food waste to microbes within optimal oxygen and moisture concentrations, thus accelerating degradation.
Rotary drums are at the high end of the technology spectrum since they continuously, or intermittently, mix food waste with carbon bulking agents such as leaves, wood chips, and nonrecyclable paper and cardboard. Large rotary drums can be 12-feet in diameter and 185-feet long, with a capital cost of more than $2 million per drum. There are also smaller drums, such as 4-feet in diameter and 8-feet long, or 10-feet in diameter and 40-feet long. The capital cost of such systems can be $40,000 to more than $150,000.
Rotary drums have been successfully utilized to compost food waste in all kinds of settings, from municipal to universities to an automobile manufacturing facility. There are probably more than 100 smaller drums operating on dairy farms in North America that convert manure into compost, as well as bedding for the cows. Drums are also used to compost animal mortalities, particularly chickens.
Less Expensive Design
Since its inception in the 1920s, the North Country School/Camp Treetops (NCS/CTT) preparatory school for students in grades 4 through 9 in Lake Placid, New York, strives to connect students to the land through environmental studies and outdoor education, forestry, organic gardening, hiking, skiing, swimming, and other activities so prevalent in the Adirondack mountains. Food scraps have been composted since the 1940s at the school and summer camp, with compost used to grow vegetables in greenhouses and gardens for the cafeteria.
Read the full article at BioCycle.net.