The different organisms do not live under the same conditions of temperature and do not eat all of the same substances.  By feeding on these materials and by digesting them, the organisms produce new materials (humus), which are consumed by others.

During the composting process, the composition changes in organic matter, and the presence of communities that are now living are not linear.

At the beginning of composting, only the micro-organisms are active.  The oxygen is consumed and the temperature rises, it is the phase of decomposition.  The micro-organisms use enzymes that destroy first the cell walls of soft tissue.  When the cell walls are pierced, the content of the cell flows and there remains a soft structure.

This is what we may call “spoil”.

Then the bacteria are at work.  Possible negative effects of decay, such as the smell of acidity are negated by the presence of structures and materials by a regular airing. Another consequence of the activity of micro-organisms is the gradual elevation of temperature. This is particularly important at the beginning of the composting process. The energy in the organic matter is transformed into heat.

In a large compost pile, the temperature can reach from 122 to 140 degrees Fahrenheit and sometimes more (158 to 176 degrees Fahrenheit in cubic meters).  Atthis temperature there is more of a rapid digestion.  The seeds of disease and other seeds that are present in the garden waste are neutralized. 

What is significant is that the decomposition phase is combined with a reduction of volume.  The reduction which occurs during the first days, after the formatting of the different layers, constitutes the work to be attributed to the self weight and loss of the structure matter.

The transformation of carbonaceous matter as CO2 volatile and the evaporation of the water are other sources of reducing the volume.

The temperature gradually decreases and the fungus colonizes the matter.  Below 86 degrees Fahrenheit, the micro organisms stay active but are now accompanied by bodies of larger sizes which are, compost worms, mites, springtails, woodlice, and millipedes .. In fact all the macros that live in the litter, live among the leaves and branches under trees or under pieces of rotten wood.

While the micro organisms continue processing waste through the droppings of their own enzymes, the decomposition by macro-organisms is happening through their own digestive tract.  Thus it happens as follows: they nibble on pieces of wood which become tender and then they suck the substance of the cells.  The material is then reduced into smaller particles that continue the decomposition process in the gastrointestinal tract and then during the colonization of excrement by micro-organisms.

The material loses entirely its original appearance; in fact we find more than crumbs.

Then other micro-organisms are at work:
The final processing of organic matter in foster elements, water and oxygen, is called mineralization.

Substances form mineral nutrients for the plant.
As the extent of decomposition of organic matter, humus is formed.