Question
How do micro organisms rot away organic material?

Answer
Dear Mikayla:

Reference: Offwell Woodland & Wildlife Trust Website

All living organisms on earth will eventually die.  Many plants naturally complete their life cycle and die within a year, but even the longer lived plants such as trees have a limited natural life span.  Nearly all animals in nature will succumb to disease, being killed or being eaten, it is very rare for any to make it to old age.  If every organism that died did not decay and rot away, the earth's surface would soon be covered in a deep layer of dead bodies that would remain intact indefinately.  A similar situation would arise if animal and plant wastes never rotted away.   Fortunately this does not happen because dead organisms and animal wastes become food or a habitat for some other organisms to live on.  Some dead animals will be eaten by scavenging animals such as foxes or crows.  Those which are not eaten by larger animals are quickly decomposed or broken down into their constituent chemicals by a host of creatures including beetles and their larva, flies, maggots and worms as well as bacteria, moulds and fungi.  Collectively these are known as decomposers.  The lives of many of these organisms depends on the death of others.

During the process of decomposition, the decomposers provide food for themselves by extracting chemicals from the dead bodies or organic wastes; using these to produce energy. The decomposers will then produce waste of their own.  In turn, this will also decompose, eventually returning nutrients to the soil. These nutrients can then be taken up by the roots of living plants enabling them to grow and develop, so that organic material is naturally recycled.  Virtually nothing goes to waste in nature.  When an animal dies and decomposes, usually only the bones remain, but even these will decompose over a much longer period of time.

Putrefactive breakdown of organic material takes place anaerobically. Organic compounds break down by the action of living organisms that do not require air in the normal sense. These organisms use nitrogen, phosphorus, and other nutrients to live and to develop cell protoplasm, but they reduce the organic nitrogen to organic acids and ammonia. The carbon from the organic compounds which is not utilized in the cell protein is liberated mainly in the reduced form of methane (CH4). A small portion of carbon may be respired as carbon dioxide (C02).

Since anaerobic destruction of organic matter is a reduction process, the final product, humus, is subject to some aerobic oxidation when put on the soil, that is, it may appear to decompose further after being exposed to air. This oxidation is minor, takes place rapidly, and is of no consequence in the utilization of the material on the soil. In other words, much less heat is generated in anaerobic decomposition than in aerobic decomposition.

The lack of heat generated in the anaerobic destruction of organic matter is a definite disadvantage if contaminated materials are used for composting. High temperatures are needed for the destruction of pathogens and parasites. In anaerobic decomposition the pathogenic organisms do eventually disappear in the organic mass, as a result of the unfavorable environment and biological antagonisms. The disappearance is slow, and the material must be held for periods of six months to a year to ensure relatively complete destruction of pathogens, such as the eggs of Ascaris, nematodes which are among the most resistant of the fecal-borne disease parasites in wastes. Therefore, make compost this year and use it next year.

Sincerely,

Mack Jean
AllExperts
Master Gardener
Tennessee