Principles of Microbial Organic Fertilizer Production and Microbiological Processes

1, Basic Principle

Aerobic fermentation is a process in which aerobic microorganisms, under aerobic conditions, decompose and oxidize part of the organic matter into simple inorganic matter through their own catabolic and anabolic processes, from which they obtain the energy needed for microbial metabolism, while converting part of the organic matter into new cellular material, allowing microorganisms to grow and reproduce, producing more organisms. The result of fermentation is the conversion of organic matter in waste to humus with a higher degree of stabilization.

2, Microbiological Process

The microbiological process of aerobic fermentation can be roughly divided into three stages, each of which has its own unique microbial taxa.

1) Heat Production Stage (medium temperature stage, warming stage)

At the early stage of fermentation (usually 1-3 days), thermophilic microorganisms in the pile use soluble and easily degradable organic matter as a source of nutrients and energy to proliferate rapidly and release heat energy, causing the temperature of the pile to rise continuously. The temperature at this stage is in the range of room temperature to 45℃, and the microorganisms are mainly medium temperature and aerobic type, usually some non-budding bacteria. There are more types of microorganisms, mainly bacteria, fungi and actinomycetes. Among them, bacteria mainly use water-soluble monosaccharides, etc., and actinomycetes and fungi have special functions for decomposing cellulose and hemicellulose substances.

2) High Temperature Stage

When the temperature of the fertilizer pile rises above 45℃, it enters the high temperature stage. Usually from the beginning of the pile fermentation, only 2-3 days the fertilizer pile temperature can quickly rise to 55 ℃, 1 week the pile temperature can reach the highest value (the highest temperature up to 80 ℃). Thermophilic microorganisms are suppressed, and thermophilic microorganisms gradually take their place. In addition to the residual and newly formed soluble organic matter from the previous stage continue to decompose and transform, complex organic matter such as hemicellulose, cellulose and protein also start to decompose strongly. At about 50 ℃ to carry out activities are mainly thermophilic fungi and actinomycetes; temperature rises to 60 ℃, fungi almost completely stop activities, only thermophilic actinomycetes and bacteria activities; temperature rises to 70 ℃ or more, most thermophilic microorganisms have been unsuitable, microorganisms die in large numbers or enter a dormant state. At this time, the heat generated decreases and the pile temperature automatically decreases. When the pile temperature drops below 70℃, the dormant thermophilic microorganisms will be active again and continue to decompose the difficult organic matter, and the heat will increase, so the pile temperature will be in a naturally regulated and long-lasting high temperature period.

The high temperature plays an important role in the rapid decomposition of fermentation, in this stage the formation of humus within the fermentation process began, and began to appear in the weak alkali dissolved black material. Through high temperature can effectively kill pathogens in organic waste, requiring the highest fermentation temperature of 50-55 ℃ or more, lasting 5-7 days.

3) Ripening Stage

At the end of the high-temperature stage, only part of the more difficult to decompose organic matter and newly formed humus, when microbial activity decreases, heat generation decreases, and the temperature drops. At this time, thermophilic microorganisms dominate again, the residual more difficult to decompose organic matter for further decomposition, humus is increasing and tends to stabilize, at this time the fermentation into the decomposition stage.

After cooling, oxygen demand is greatly reduced, fertilizer pile void increases, oxygen diffusion capacity is enhanced, at this time only need natural ventilation. In the forced ventilation fermentation common after-ripening treatment, that is, the aeration pile turned once, stop the aeration, let it decay. It can also play the role of nitrogen retention.