Bio-incubation under aerobic conditions

Currently, in order to reduce the problem of pollution from polluting landfills, bio-composting technologies are available to replace the traditional landfill method. At the same time, this is also a solution to reduce the amount of toxic waste released into the environment. Let’s learn about <aerobic composting of organic solid waste> to solve the problem of waste treatment in daily life.

The aerobic composting process of organic solid waste is the biological transformation and stabilization of organic matter in the presence of oxygen with the participation of aerobic microorganisms (VSV). The products of the process are CO2, water, heat, stable humus, and do not carry pathogens. During decomposition, complex organic compounds are first broken down into simpler substances. Nitrogen and carbon compounds are decomposed into CO¬2, NH4, organic acids and molecular nitrogen, respectively.

During decomposition, complex organic compounds are first broken down into simpler substances. Nitrogen and carbon compounds are decomposed into CO¬2, NH4, organic acids and molecular nitrogen, respectively. The mechanism of aerobic biotransformation takes place as follows:

– For compounds of nitrogen: Protein → Peptides → Amino Acid

→ Ammonium compounds → Bacteria → Molecular nitrogen.

For carbon compounds:

Hydrocarbons → sugar molecules → organic acids → CO2 and bacteria. 

The biochemical metabolic reactions that take place during aerobic incubation are very complex, all carried out by the enzymes of microorganisms present in the incubation. The biochemical reactions occurring in aerobic incubation are characterized by the equation:

COHNS + O2 + aerobic microorganisms → CO2 + NH3 + other products + energy. 

Factors affecting the aerobic bio-incubation process:

  1. Size and composition of annealing material:

The size of the material greatly affects the rate of decomposition because the aerobic decomposition of microorganisms occurs on the surface of organic materials. Therefore, reducing the size of the incubation material will increase the contact surface, increase the activity of bacteria, and accelerate the decomposition rate. However, if the size of the material is too small and tight, it will limit the air circulation in the pile and reduce the level of VSV activity. The optimum size for the process of organic matter is 3-5cm.

  1. Porosity of annealing material

Porosity is an important factor in the production of organic fertilizers. Porosity directly affects the oxygen supply necessary for the metabolism and respiration of aerobic microorganisms and the oxidation of organic particles present in the compost. Normally, porosity for manure production to take place is 35-60%, optimally 32-36%.

  1. Annealing temperature and time

Incubation temperature can greatly affect the incubation process because temperature has an impact on aerobic microbial activity. The optimum temperature for annealing is 40-550C.

Note: If the temperature in the compost pile is not guaranteed, moisture-loving, thermophilic bacteria will not appear. cannot kill pathogenic microorganisms, affecting the quality of compost. If the heat is too high, it will lead to the depletion of water in the compost pile, causing the primary bacteria to die, reducing the efficiency of the incubation process. The incubation time should be consistent with the temperature of the compost pile. If the composting time is too short, the decomposition process has not been completed and the quality of the compost is not satisfactory. But if the incubation time is too long, it requires a large incubation tank area, which is not economically efficient.

  1. pH

pH is an important parameter affecting aerobic incubation. pH affects the absorption of nutrients, the activity of microorganisms and the dissolution of heavy metals. Bacteria usually grow well at pH = 6.5-8 and fungi at pH = 5-8.5. In the compost pile, the pH changes with the incubation time. The initial stage pH is usually around 6.0, then decreases to 4.5-5 due to organic acid production for a few days, then increases to 7.5-8.5 as the temperature increases. At the end of incubation, the pH decreased to a neutral level of 5.5-6.5.

  1. Humidity

Moisture is essential for the activity of microorganisms in the composting process because water is necessary for the dissolution of nutrients into the cell cytoplasm.

The optimum humidity for incubation is 50-60%. With urban waste with relative humidity in the range of 40-60%, it is very suitable for the composting process. However, the optimal moisture content can vary depending on the nature of the organic matter in the compost pile, to achieve high performance it is necessary to control the humidity at 40-60% during the composting process.

  1. Oxygen Distribution

Oxygen plays an important role in the metabolism and oxidation of organic matter present in the composting material. When VSV oxidizes carbon to produce energy, oxygen is used and CO2 is produced. In the absence of oxygen, the process will occur in anaerobic conditions, creating odors due to the production of H¬2S gas. If enough oxygen is provided, the microorganisms will rapidly decompose organic compounds, reduce the initial high moisture content in the litter, and have a cooling effect in the compost pile. Aerobic microorganisms can survive at 5% oxygen concentration, 10% oxygen concentration is optimal for aerobic incubation. Air is supplied to the compost mass in several ways, such as agitation, use of air ducts, dumping of waste from upper to lower reservoirs, forced aeration. 


The information is contained in the report “Bio-composting technologies for organic solid waste treatment” made by a team of authors including staff from Green Development Support Center (Greenhub) and experts from the National University of Civil Engineering within the framework of the Green Bay project 2020.

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