Composting is a controlled, biological process of decomposing raw organic waste materials such as dead leaves and kitchen scraps. Microorganisms including bacteria, fungi, and worms break them down to compost, a nutrient-rich soil amendment. 

In the active phase of composting, metabolic work of microorganisms rapidly heats up the compost pile to temperatures typically in the range of 50-65°C (120-150°F), high enough to kill pathogens and toxic compounds to plants.

When the active phase subsides, the temperatures gradually decline to about 100°F and also the rate of oxygen consumption to a level where the compost pile can remain stockpiled without much turning. Under an optimal condition of oxygen, moisture, pH, and salinity levels, the compost pile can undergo months of final composting period which would be concluded by the time of complete conversion of organic materials to humic substances resistant to microbial decomposition.