Submitted to: Principles and Applications of Soil Microbiology
Publication Type: Book / Chapter
Publication Acceptance Date: April 13, 2004
Publication Date: July 15, 2004
Citation: Zibilske, L.M. 2004. The microbiology of composts. Sylvia, D., Fuhrmann, Hartel, P., Auberer, editors. 2nd edition Prentice Hall, Upper Saddle River, New Jersey. Principles and Applications of Soil Microbiology. Chapter 23.
Interpretive Summary: Composting is the biological decomposition and stabilization of organic substrates under conditions that allow development of thermophilic temperatures as a result of biologically-produced heat to produce a final product that is stable, free of pathogens and plant seeds, and can be beneficially applied to land. The processes are characterized by a period of rapid decomposition and self-heating followed by a cooler, slower decay of remaining organic substrates. Regulating the kinds of organic substrates and controlling the physical and chemical attributes of the decomposition environment in the compost pile facilitate the process. Manipulating moisture content, pH, nutrient concentrations, and oxygen can bring about increased decomposition rates and change the characteristics of the compost. The same microbial processes are used by both large commercial composting industries and by backyeard gardeners, although the former may produce thousands of cubic yards of compost while the latter only a few. Today, enhancements in modern engineering have resulted in the growing use of composting for municipal and industrial waste treatment and nutrient recovery.
Composting is a microbial process in which organic matter progresses through stages of decomposition and stabilization in a relatively short time. It is characterized by an early period of self-heating in which heat generated by rapid microbial metabolism is produced faster than it can dissipate from the site of decomposition. Temperature increases and substrate changes elicit a succession of microorganisms that reflect the change from mesophilic to thermophilic stages. During the curing phase, mesophilic conditions return and further decomposition stabilizes the compost. The purposes of composting wastes range from volume reduction to sanitization of the wastes. Applied to land, finished compost can function as a slow-release fertilizer and soil-improving amendment. Interest in composting has increased greatly, and has led to the development of many engineering design modifications. Computerized control and large physical facilities designed to enhance the processing of large amounts of municipal and industrial wastes are now commonplace.