The Fermentation Process of Organic Compost can be Simply Divided into the Following 4 Stages

1. Heat Generation Stage
At the early stage of compost making, the microorganisms in the compost are mainly medium-temperature, aerobic species, the most common being non-bacterium, bacterium and mold. They start the fermentation process of compost, under aerobic conditions exuberant decomposition of easily decomposable organic substances (such as simple sugars, starch, protein, etc.), generating a large amount of heat, and constantly increase the temperature of compost, from about 20 ℃ to 40 ℃, known as the heat stage, or medium temperature stage.

2. High Temperature Stage
As the temperature increases, the good heat microorganisms gradually replace the medium-temperature species and play a leading role, the temperature continues to rise, generally within a few days that is more than 50 ℃, into the high-temperature stage. In the high temperature stage, thermophilic actinomycetes and thermophilic fungi become the main species. They decompose the complex organic substances (such as cellulose, hemicellulose, pectin substances, etc.) in the compost strongly, heat accumulation, compost temperature rises to 60-70℃, even up to 80℃. Immediately thereafter, most thermophilic microorganisms also die in large numbers or enter a dormant state (more than 20d), which has a very important role in accelerating the decay of compost. Improperly composted compost, only a very short period of high temperature, or simply can not reach high temperature, and thus slow decomposition, in half a year or longer period of time still can not reach the semi-rotten state.

3. Cooling Stage
When the high temperature stage lasts for a certain period of time, cellulose, hemicellulose, pectin material has been mostly decomposed, leaving complex components that are difficult to decompose (such as lignin) and newly formed humus, microbial activity is weakened, and the temperature gradually decreases. When the temperature drops below 40°C, mesophilic microorganisms become the dominant species again.

If the cooling stage comes early, it indicates that the pile conditions are not ideal and the decomposition of plant matter is not sufficient. At this time, the pile can be turned and the pile material mixed to produce a second heat-up and warming to promote the decomposition of compost.

4. Decomposition and Fertilization Stage
After the compost has rotted, the volume shrinks, the pile temperature drops to slightly above the temperature, then the compost should be pressed tightly, resulting in an anaerobic state, so that the mineralization of organic matter is weakened, in order to facilitate fertilization.

Composting is actually a form of waste stabilization, but it requires special humidity, aeration conditions and microorganisms to produce the right temperature. Studies have shown that heating at a certain temperature for a period of time can destroy pathogens, weed seeds. Usually heating at a temperature of 60°C-70°C (humid heat) for 5-10min. can destroy the activity of non-sporulating bacteria and non-dormant bodies of bacteriophages. Using heat sterilization, heating at 70°C for 30min can destroy the pathogens in sludge. However, at lower temperatures (50°C-60°C), the inactivation of some pathogenic bacteria can be up to 60 d. Therefore it is necessary to maintain the temperature above 60°C for a period of time during composting. The decomposition rate of residual organic matter after reasonable composting is low, relatively stable and easy to be absorbed by plants. The odor can be greatly reduced after composting.