|
The
Composting Process
Prepared by Charles W. Marr,
Extension Horticulturist, Vegetable Crops
Composting is the biological decomposition
of organic materials. Decomposition occurs naturally. However, in the composting
process natural decomposition is accelerated and improved by human intervention.
An understanding of the process can lead to better products and fewer problems.
Microorganisms
Decomposition is carried
out by microorganisms and invertebrates. They utilize yard and food wastes as
a source of energy and require oxygen and water to survive. In the process of
decomposition, carbon dioxide, heat, water and soil-enriching compost
(partially decomposed organic materials) result. Heat produced in the
composting process can be as warm as 150° to 160° F. The increased
temperature results in increased water evaporation. Monitoring the temperature
of the pile is a way of determining the success of the composting process.
After organic materials are decomposed, the temperature of the pile gradually
lowers to ambient temperatures. The weight and volume of the compost pile is
reduced. This is another way of measuring the effectiveness of the composting
process.
Microorganisms that are
involved in composting include a wide range of naturally occurring organisms
including bacteria, fungi, molds, actinomycetes, and protozoa. Other small
invertebrate animals such as mites, millipedes, insects, earthworms, and other
similar organisms can also be involved. A wide range of different organisms is
usually preferred since there is a better chance that a complete composting
process will occur. However, aerobic bacteria are the primary organisms that
cause decomposition of materials in a compost pile.
Aerobic versus Anaerobic
Most organisms preferred for the
composting process are aerobic (requiring oxygen) since they provide rapid,
complete composting. Other organisms can operate without oxygen or anaerobic
conditions. Sometimes this process is called fermentation and usually occurs
more slowly. However, the greatest limitation to anaerobic organism is that
odors usually are produced which can be quite offensive. It is also possible
to generate acids and alcohols which may be harmful to some plants. If you
notice a serious bad smell from your compost pile, chances are it needs a
greater level of oxygen (which can be created by turning or agitating the
pile).
Temperature
Aerobic bacteria vary in the
temperatures at which they can survive. Some can survive temperatures of 140°
to 150° F and are called thermophilic bacteria. As the composting process
starts, lower temperature requiring bacterial species predominate until
temperatures increase to a level that they are killed. Then thermophilic
bacteria take over and predominate. Thermophilic bacteria are eventually
killed by the ever increasing temperatures of the compost pile. As this
occurs, the temperature of the pile decreases and lower temperature bacteria
begin to take over again. Finally, when most of the material has been
composted and the bacteria no longer have an energy source, they die and the
composting process is complete.
Composting
A complex 'web of life' exists in the
compost pile where various organisms are feeding on the organic materials or
on other organisms in the pile. Certain mobile organisms, such as worms may
move away from the excessive heat of the center of the pile then move back
when the pile cools. Most harmful organisms, such as disease organisms or
persistent insect pests, as well as weed seeds are killed in the composting
process.
Kansas State University Cooperative
Extension Service Path:
Home>Education>Environment
Information>The
Composting Process
|
