The principle of thermal inactivation of organic fertilizer compost

Many substrates used for composting carry pathogens of humans, animals and plants, as well as weed seeds, and the sludge after urban sewage treatment is a typical substrate that carries pathogens. During the composting process, the growth of these organisms can be effectively controlled through continuous heating for a short period of time. Therefore, one of the main advantages of high-temperature composting is the ability to inactivate pathogens and seeds.

Cell death is largely based on thermal inactivation of enzymes. At a suitable temperature, the inactivation of the enzyme is reversible, but it is irreversible at high temperatures. The thermodynamic point of view shows that the active part of the enzyme will decrease rapidly in a small temperature range. Without the action of enzymes, cells will lose function and die. Only a few enzymes can withstand long periods of high temperature.

Studies have shown that heating at a certain temperature for a period of time can destroy pathogens or organisms. Usually at 60~70℃ (damp heat), heating for 5~10min can destroy the activity of non-spore bacteria and non-dormant bacteria of spore bacteria. Data show that using heat sterilization, heating for 30 minutes at 70°C can eliminate pathogens in the sludge. However, at lower temperatures (50~60°C), it takes up to 60 days to inactivate some pathogens, so it is necessary to maintain a temperature above 60°C during the composting process.