Turning should continue until the temperature fails to rise. This indicates that the compost material is biologically stable. Sustained temperatures above 130 degrees Fahrenheit favors destruction of pathogenic bacteria, viruses, fly larvae and weed seeds that might be present in the waste. N ratio, or a decrease in oxygen supply, the temperature may drop and the microbial population will shift back to a regime of lower temperature microbes, causing the compost pile to go anaerobic. Aeration in the composting process is critical.
Proper aeration introduces oxygen and evacuates excess heat, gas and moisture.
As oxygen becomes depleted, microbial growth will slow and the temperature of the mass will decrease. Proper aeration may be achieved by passive air exchange, forcing air through the material or mechanical turning. In addition, aeration minimizes nitrogen loss by denitrification. This may result in unpleasant odors, and loss of fertilizer value. For animal carcass disposal, aerobic composting is preferred because it is faster and produces less odors.