If the microbes are supplied with the conditions they need to stay active, they will efficiently decompose raw materials. See Figure 1 for a graphical representation of the process. Manure, the most abundant agricultural compost ingredient, is high in nitrogen and relatively wet. It's a narrow, low pile with a large surface area exposed to encourage aeration, or addition of oxygen. As the microorganisms decompose the organic material, they produce carbon dioxide, heat, and water.
Heat is released as a result of the microbial activity.
Actively composting materials maintain temperatures between 120 and 140 degrees. Many composters monitor the activity of the microorganisms by monitoring temperature. See Figure 2 for a look at the process of composting. The compost pile or windrow shrinks as the product becomes drier. It contains beneficial microorganisms, humified organic material, and slow-release forms of nitrogen.