Organic Gardener's Composting by Steve Solomon

Frequent turning with machinery keeps the heap working rapidly. During the initial experiments the turning was done with a tractor and front end loader. These days giant "U" shaped machines may roll down windrows at municipal composting plots, automatically turning, reshaping the windrow and if necessary, simultaneously spraying water.

Some municipal waste consists of moist kitchen garbage and grass clippings. Most of the rest is dry paper. If this mixture results in a moisture content that is too high the pile gets soggy, sags promptly, and easily goes anaerobic. Turning not only restores aerobic conditions, but also tends to drop the moisture content. If the initial moisture content is between 60 and 70 percent, the windrow is turned every two days. Five such turns, starting two days after the windrow is first formed, finishes the processing. If the moisture content is between 10 and 60 percent, the windrow is first turned after three days and thence at three day intervals, taking about four turns to finish the process. If the moisture content is below 40 percent or drops below 40 percent during processing, moisture is added.

No nuisances can develop if turning is done correctly. Simply flipping the heap over or adding new material on top will not do it. The material must be blended so that the outsides are shifted to the core and the core becomes the skin. This way, any fly larvae, pathogens, or insect eggs that might not be killed by the cooler temperatures on the outside are rotated into the lethal high heat of the core every few days.