The Basics of Composting

Composting is a natural biological process of decomposition of organic materials, historically in a predominantly aerobic environment. Enhancing basic composting with forced aeration that mechanically moves fresh oxygen-rich air up through the composting pile, evenly and at pre-determined intervals, optimum aerobic conditions are created throughout the duration of the composting process. Forced aeration removes one of the limiting factors associated with the traditional static pile composting process – the lack of oxygen within the pile – and results in maximum decomposition of the waste material in a minimum amount of time.

During the process, bacteria, fungi and other microorganisms break down organic materials to a stable mixture called compost while consuming oxygen and releasing heat, water, and carbon dioxide (CO2). The finished compost resembles humus and can be used as a soil amendment. Composting reduces the volume of the parent materials and pathogens are destroyed if the process is controlled properly.

All disease-causing organisms are subjected to at least three adverse conditions during composting: heat, toxicity caused by products of decomposition, and microbial antagonism. Heat generated in the composting process is the primary determinant studied as the in-activator of disease-causing organisms. Heat is also the performance indicator of microbial activity within the composting pile. An extended period of heat (minimum of 5 consecutive days) in the desired range (above 140°F) achieved during composting is essential for the destruction of most pathogens. With proper management, the forced aeration composting process will produce temperatures consistently higher than the typical static pile composting pile as noted earlier. Higher temperatures translate into higher microbial activity, reduced retention time in each bin and better pathogen reduction. Normal temperatures for forced aeration are typically in the range of 140°F to 150°F for 10 or more consecutive days.

The effect of pH and the action of other bacteria and fungi on the destruction of disease-causing organisms is still largely unknown. Only minimal research has been done with disease-causing organisms of animals with regard to the ability of the composting process to destroy them. A recent review of chemical and microbial hazards to humans from urban waste composting facilities indicates that the assumption that all disease-causing organisms are killed by composting may be faulty.

All living organism require carbon, nitrogen, oxygen, hydrogen, and many other elements to survive. Any requirement that is not met will limit the growth, reproduction, and ultimate survival of the organism. Composting is focused on understanding and meeting the needs of the organisms that are actually doing the composting. While composting occurs naturally, the process requires proper conditions to occur rapidly, minimize odor generation, and prevent nuisance problems. Over 20 controllable factors affect composting. View our table that lists eight of those factors and acceptable ranges to aim for when composting. Of these factors, the four major factors to be controlled in the composting process are the material mix (nutrient balance), water content, porosity or aeration, and temperature.