Composting and Microorganisms


Composting is the process of decomposing raw organic materials into compost. Compost is a nutrient-rich material that adds nutrients and organic matter to your garden soil. This improves the fertility of the soil as well as the structure, making it porous and reducing nutrient runoff during irrigation.


Chemical decomposing microorganisms are bacteria, fungi and actinomycetes that live in the compost pile during the decomposition process, says the University of Illinois Extension. The microorganisms change the chemical properties of organic wastes. Larger macroorganisms such as mites, spiders, slugs, beetles and ants are considered physical decomposers. They suck, bite and grind the organic material into smaller pieces.

Aerobic Bacteria

Aerobic bacteria are the most abundant microorganisms. They are so small that you would need 25,000 laid end to end to make an inch, and over a million may live in one gram of soil. They are able to eat anything. The bacteria eat carbon to build up energy in their bodies. As their bodies gain energy, they begin producing heat. This process heats up the compost pile. As these aerobic organisms die, their bodies become further material to decompose. The rise in temperature creates the proper conditions for more organisms to grow and thrive.


As the pile decomposes, oxygen is needed to regulate the pile's temperature and hasten the decomposition process. Too much heat, as well as a lack of oxygen, kills microorganisms. Regular turning with a pitchfork will fluff the pile and add oxygen, says the University of Illinois.


Microorganisms need water to live. According to the University of Illinois, microbial activity works best through a thin film of water. Microorganisms are better able to utilize organic molecules that are dissolved into water. When moisture is below 40 percent, bacteria slow down and become dormant. Over 60 percent moisture in the pile drowns the microbes.

Particle Size and Volume

The size of the items in the pile determines how quickly everything breaks down. If the pile has more surface area than depth, the pile will decompose quicker. Smaller pieces of material allow microorganisms to break down material quickly. Cutting materials with a knife or mower before putting it into a pile will keep pieces small.

Keywords: Composting, Microorganisms, Composting science

About this Author

Cleveland Van Cecil is a freelancer writer specializing in technology. He has been a freelance writer for three years and has published extensively on, writing articles on subjects as diverse as boat motors and hydroponic gardening. Van Cecil has a Bachelor of Arts in liberal arts from Baldwin-Wallace College.