Changes in Temperature During Composting of Organic Fertilizer

Composting is the process of mixing a certain percentage of composting base material and filler material, under the appropriate temperature, humidity and ventilation conditions, so that organic matter is degraded by microorganisms to form stable humus and minerals, and release heat, after composting the product is organic fertilizer. Composting is a fermentation process closely related to temperature, including four periods: warming period, high temperature period, cooling period and decomposition period.

First, The Warming Period

The warming period is dominated by bacteria, fungi, actinomycetes and other mesophilic microorganisms, which mainly decompose and use soluble substrates such as sugars, starchy organic matter to release some NH3 while emitting large amounts of heat. When the temperature reaches 25 degrees, thermophilic microorganisms rapidly reproduce and grow, and can reach 40~45 degrees at about 20H. The temperature exceeds 45~50 degrees, marking the high temperature period of composting.

Second, The High Temperature Period

With the increase of temperature, mesophilic microorganisms gradually lose their activity, which is replaced by thermophilic microorganisms such as Bacillus and actinomycetes.

Bacillus is the representative bacteria of the high temperature stage of compost, they can form a very thick spore wall to resist high temperature, radiation and chemical corrosion and other adverse conditions.

Actinobacteria can break down some cellulose, dissolve lignin, and tolerate higher temperatures and pH than fungi. Actinomycetes are not as strong as fungi in degrading cellulose and lignin, but they are the dominant group of lignocellulosic decomposing bacteria during the high temperature period of composting Under adverse conditions, actinomycetes survive in the form of spores. Nocardia, Streptomyces, high-temperature actinomycetes and monospora (Micromonospora) are thermophilic actinomycetes that are dominant in composting, not only in the high-temperature phase of the composting process, but also in the cooling phase and maturation phase, where cellulose, hemicellulose, lignin and some protein-like complex organic compounds begin to be gradually oxidized and decomposed.

As the temperature rises during the high temperature period, the microbial populations that play a role are also gradually changing, thermophilic fungi and actinomycetes are active in the environment of about 50 degrees, 60 degrees because the fungal activity completely stopped, the thermophilic actinomycetes and bacteria continue to be active, when the temperature is higher than 70 degrees, the majority of thermophilic bacteria dormant or dead, organic matter decomposition under the action of enzymes, the degradation rate becomes slower.

Therefore, the best temperature of composting high temperature period should be 55~60 degrees, this interval is rich in microbial species and the number of microorganisms and the best activity, can ensure a high rate of organic degradation, and at the same time can kill the parasites, pathogenic microorganisms and harmful bacteria in the raw materials of composting, to achieve the harmless compost.

Third, The Cooling Period

Composting late, easy to degrade the nutrients are basically consumed completely, thermophilic microbial activity decreases, heat release decreases. When the temperature gradually decreases to below 50 degrees, the number of thermophilic microorganisms such as yeast, actinomycetes and nitrifying bacteria increases, thus further decomposing the hard-to-degrade organic matter. During the period, humus and fulvic acid content increases and tends to stabilize, oxygen demand decreases and water content decreases.

Fourth, The Decomposition Period

Compost temperature gradually decreases to the same temperature as the environment, the compost enters the decomposition period. Organic material has been decomposed and stabilized in large quantities, humus and nutrients in the fertilizer, especially the content of N fertilizer increased significantly.