(1) Fever stage In the early stage of composting, the microorganisms in the compost are mainly of moderate temperature and aerobic types. The more common ones are non-spore-forming bacteria, spore-forming bacteria and mold. They start the fermentation process of composting. Under aerobic conditions, they vigorously decompose and easily decompose organic substances (such as simple sugars, starches, proteins, etc.) to generate a lot of heat. For the fever stage, or the middle temperature stage.
(2) High temperature stage As the temperature increases, the heat-bearing microorganisms gradually replace the mesophilic species and play a leading role. The temperature continues to rise, generally reaching more than 50 ° C within a few days, and enters the high temperature stage. In the high temperature stage, thermophilic actinomycetes and thermophilic fungi become the main species. They strongly decompose complex organic substances (such as cellulose, hemicellulose, pectin substances, etc.) in the compost, heat accumulation, the temperature of the compost rises to 60-70 ° C, and even up to 80 ° C. Then most of the good heat Microorganisms also die in large numbers or enter a dormant state (more than 20 days), which has an important role in accelerating the compost maturation. Improperly composted compost only has a short high temperature period, or does not reach high temperature at all, so it matures slowly, and it cannot reach a semi-mature state in half a year or more.
(3) Cooling stage When the high temperature stage lasts for a certain period of time, most of the cellulose, hemicellulose and pectin substances have been decomposed, leaving complex components that are difficult to decompose (such as lignin) and newly formed humus Activity weakens and the temperature gradually decreases. When the temperature drops below 40 ° C, the mesophilic microorganisms become the dominant species again. If the temperature comes down early, it indicates that the stacking conditions are not ideal and the plant matter is not decomposed sufficiently. At this time, the pile can be turned over, and the accumulated materials can be mixed well to generate a second heat and temperature increase to promote the composting of the compost.
(4) Stage of maturing and composting After composting, the volume of the compost is reduced, and the temperature of the compost is reduced to slightly higher than the temperature. At this time, the compost should be compacted, causing an anaerobic state, and weakening the mineralization of organic matter, so as to facilitate fertilizer preservation.
In short, the fermentation process of organic compost is actually the process of metabolism and reproduction of various microorganisms. The metabolic process of microorganisms is the process of decomposition of organic matter. The decomposition of organic matter will inevitably produce energy, which drives the composting process, raises the temperature, and at the same time dries the wet substrate. Many composting substrates carry human and animal and plant pathogens, as well as annoying organisms such as weed seeds.
During the composting process, by continuously heating for a short time, the growth of these organisms can be effectively controlled. Therefore, a major advantage of high-temperature composting is its ability to inactivate human and animal and plant pathogens and seeds. Pathogens and seeds are inactivated due to cell death, and cell death is largely based on the thermal inactivation of enzymes. At an appropriate temperature, the enzyme inactivation is reversible, but at high temperatures it is irreversible. Within a very small temperature range, the active part of the enzyme will rapidly decrease. If there is no enzyme, the cell will lose its function and die. Only a few enzymes can withstand the long-term high temperature. Therefore, microorganisms are very sensitive to heat inactivation.
Studies have shown that heating at a certain temperature for a period of time can destroy pathogens or annoying organisms. It is usually heated at 60-70 ° C (damp heat) for 5-10 minutes. Can destroy the activity of non-spore bacteria and non-dormant bodies of spore bacteria. Using heat sterilization, heating at 70 ° C for 30min can eliminate pathogens in sludge. However, at lower temperatures (50-60 ° C), some pathogens can survive up to 60 days. Therefore, it is necessary to maintain a temperature above 60 ° C for a period of time during the composting process. During the composting process, the pile should be turned over if necessary. Generally, it takes place when the reactor temperature crosses the peak and begins to cool down. Turning the reactor can remix the materials with different decomposition temperatures in the inner and outer layers. If the humidity is not enough, some water can be added to promote the compost to rot evenly.