Compost fermentation process

Compost fermentation process

Composting is actually a form of waste stabilization, but it requires special humidity, aeration conditions and microorganisms to produce a suitable temperature. It is generally believed that this temperature is higher than 45°C. Maintaining this high temperature can inactivate pathogenic bacteria and kill weed seeds. After reasonable composting, the residual organic matter has a low decomposition rate, is relatively stable, and is easily absorbed by plants. The odor can be greatly reduced after composting.

There are many different types of microorganisms involved in the composting process. Due to changes in raw materials and conditions, the number of various microorganisms is constantly changing, so no microorganisms always dominate the composting process. Every environment has its own specific microbial flora, and the diversity of microorganisms makes composting avoid system breakdown even when external conditions change.

The composting process is mainly carried out by the action of microorganisms, which are the main body of composting fermentation. There are two sources of microorganisms involved in composting: one is the original large number of microorganisms in the organic waste; the other is the artificially added microbial inoculant. These strains have a strong ability to decompose certain organic wastes under certain conditions. They have the characteristics of strong activity, fast reproduction, and rapid decomposition of organic matter. They can accelerate the process of composting reaction and shorten the time of composting reaction.

Composting is generally divided into two types: aerobic composting and anaerobic composting. Aerobic composting is the decomposition process of organic materials under aerobic conditions. Its metabolites are mainly carbon dioxide, water and heat. Anaerobic composting is the decomposition process of organic materials under anaerobic conditions. The final metabolite of anaerobic decomposition is methane. , Carbon dioxide and many low molecular weight intermediate products, such as organic acids.

The main types of microorganisms involved in the composting process are bacteria, fungi and actinomycetes. These three kinds of microorganisms have mesophilic bacteria and thermophilic bacteria.

During the composting process, the microbial population changes alternately as the temperature changes as follows: low- and medium-temperature flora is mainly transformed into medium-high temperature flora, and medium-high temperature flora is mainly transformed into medium-low temperature flora. With the extension of composting time, bacteria gradually decrease, actinomycetes gradually increase, and molds and yeasts are significantly reduced at the end of composting.

Fermentation process of organic compost

1.Fever phase. In the initial stage of compost production, the microorganisms in the compost are mainly of medium temperature and aerobic species, and the most common ones are non-spore bacteria, spore bacteria and molds. They start the composting fermentation process, decompose easily decomposable organic substances (such as simple sugars, starch, protein, etc.) under aerobic conditions, generate a lot of heat, and continuously increase the composting temperature from about 20°C to 40°C. It is the fever stage, or the middle temperature stage.

2.High temperature stage With the increase of temperature, thermophilic microorganisms gradually replace the mesophilic species and play a leading role. The temperature continues to rise, generally reaching above 50°C within a few days, entering the high temperature stage. In the high temperature stage, thermoactinomycetes and thermogenic fungi become the main species. They strongly decompose the complex organic substances in the compost (such as cellulose, hemicellulose, pectin substances, etc.), accumulate heat, and the compost temperature rises to 60-70°C, even as high as 80°C. Then most of them are hot. Microorganisms also die in large numbers or enter a dormant state (above 20 days), which plays an important role in accelerating the maturity of compost. Improper composting has only a short period of high temperature, or it does not reach high temperature at all, so it matures very slowly, and cannot reach a semi-ripe state in half a year or longer.

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, and the activity of microorganisms is weakened , The temperature gradually drops. When the temperature drops below 40°C, mesophilic microorganisms become the dominant species again

If the cooling stage comes early, it indicates that the composting conditions are not ideal and the plant material is not fully decomposed. At this time, you can turn over the pile and mix the accumulated materials to make them generate a second heat and temperature to promote the maturity of the compost.

4.The stage of decomposing and maintaining fertilizer. After the compost is decomposed, its volume shrinks and the temperature of the compost drops slightly higher than the temperature. At this time, the compost should be compacted to cause an anaerobic state and weaken the mineralization of organic matter to facilitate fertilizer retention.

In short, the fermentation process of organic compost is actually a 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 generate energy, which promotes the composting process, increases the temperature, and can also dry the wet substrate.

Many substrates used for compost carry human, animal and plant pathogens, as well as annoying organisms such as weed seeds. During the composting process, the growth of these organisms can be effectively controlled through continuous heating for a short time. Therefore, one of the main advantages of high-temperature composting is that it can inactivate human and animal and plant pathogens and seeds.

During the compost making process, the pile should be turned if necessary. Generally, it is carried out when the temperature of the pile exceeds the peak and begins to drop. Turning the pile can remix the substances with different decomposition temperatures in the inner and outer layers. If the humidity is insufficient, add some water to promote the uniform maturity of the compost.