Author: Jeanette Thurston-Enriquez, USDA Agricultural Research Service Scientist, jthurston2@unl.edu

Pathogens are reduced from 90% to 99.999% by appropriate composting that includes such factors as temperature levels, water potential, and compost turning.

Temperatures should reach greater than or equal to 55 degrees Celsius or 131 degrees Fahrenheit for an extended period. This period depends on the type of compost pile. For example, a windrow needs to maintain 55 degrees Celsius for at least 15 days in combination with at least five turnings during this period. In addition to high temperatures and low water potential (low water potential will inhibit bacterial colonization), microbial competition within the compost will also inhibit pathogen survival. Non-pathogenic microorganisms within the compost can out-compete pathogens for consumption of available nutrients.

Appropriate composting means not only achieving the temperatures mentioned earlier but also the length of treatment time and pile turning. These factors are very important in pathogen reduction. Pile turning is very important since the high temperatures will not likely reach the outside and edges of the pile. By turning the pile, all of the compost material is adequately heated.