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Decomposition is a natural process

Natural products that were once part of a living organism, such as wool, wood, paper (uncoated) cardboard, cotton, bones, are not only food for a host of insects and other creatures but will slowly rot if the conditions are right.

Composting and decomposition is a completely natural process, which is happening all around us everyday. Decay is often seen as a negative process rather than a thriving process of change, involving millions of organisms busily recycling organic matter, creating a nutrient rich substance to feed the cycle of growth.

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All organic matter decomposes in the right conditions

If you get the proportion of the materials you put together in a pile right, then composting happens optimally. The mix of greens (the wet, soft, green materials, high in nitrogen) and browns (the dry harder, absorbent materials high in carbon). This mixture then needs to be moist and have enough air.

The decay of organic matter involves more than the physical shredding and chopping into microscopic pieces. It's also the chemical and biological transformation. Most of this transformative work is done by micro-organisms, though some larger organisms including various insects and earthworms can also be involved at different stages.

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Decomposition is an exothermic process - it generates heat

In the process of composting, microorganisms break down organic matter and produce carbon dioxide, water (leechate), heat, and humus - the relatively stable organic end product (compost). Under optimal conditions, composting proceeds through three phases:

1) the mesophilic, or moderate-temperature phase, which lasts for a couple of days,

2) the thermophilic, or high-temperature phase, which can last from a few days to several months, and finally,

3) a several-month cooling and maturation phase.

Bacteria are the smallest living organisms and the most numerous in compost; they make up 80 to 90% of the billions of microorganisms typically found in a gram of compost. Bacteria are responsible for most of the decomposition and heat generation in compost. They are the most nutritionally diverse group of compost organisms, using a broad range of enzymes to chemically break down a variety of organic materials.

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Decomposition drastically reduces the volume of organic matter

A composting process that operates at optimum performance will convert organic matter into stable compost that is odor and pathogen free, and a poor breeding substrate for flies and other insects. In addition, it will significantly reduce the volume and weight of organic waste as the composting process converts much of the biodegradable component to gaseous carbon dioxide.

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The process of decomposition releases a liquid called leechate

Composting produces a natural liquid residue (leechate) which can be highly polluting - if if it is mixed with inorganic and toxic matter, as is the case in the landfill. But leechate produced in organic decomposition can be diluted and used as fertilizer.

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Decomposition produces smelly gases only if there is insufficient oxygen.

Many microbes need oxygen, just as animals need oxygen. During the early stages of composting, the oxygen-loving microbes predominate. The microbes combine the oxygen with the carbon from the decaying matter. In that way the microbes produce energy in the form of heat. This makes the compost pile warm.

aerobic composting:
organic materials + oxygen + water = carbon dioxide + water + energy

If the oxygen in the pile is not replenished by stirring or aeration, the microbes that do not need oxygen tend to take over. These are the anaerobic bacteria.They do not produce heat. They do produce a good deal of ammonia, that gives off a tell-tale smell. The ammonia is a waste product; it comes from the microbes as they seek to discard the unneeded nitrogen in their small bodies. Another gas that can get produced in this anaerobic state is hydrogen sulfide, which smells like rotten eggs.

anaerobic composting:
organic materials + water = carbon dioxide + methane + hydrogen sulfide + energy

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