Aerobic fermentation is the core technology for organic waste resource utilization. Whether it is livestock manure, kitchen waste, or municipal sludge, all materials in a composting tank undergo a temperature-driven four-stage evolution process dominated by microorganisms.
Understanding the scientific logic of these four stages not only helps operators precisely control process parameters but also maximizes fermentation efficiency and ensures organic fertilizer quality. This article provides an in-depth analysis of the mesophilic (heating) phase, thermophilic (high-temperature) phase, cooling phase, and maturation phase, revealing the microbial activity patterns and key control points of each stage.
Temperature – The "Dashboard" of the Fermentation Process
In aerobic fermentation, temperature is the most intuitive and core process indicator. Temperature changes within the compost pile essentially reflect the succession of microbial communities and the progress of organic matter degradation.
The temperature curve inside the composting tank is like a "dashboard," telling operators which stage the fermentation is in, how active the microorganisms are, and whether intervention is needed. From ambient temperature to 60-70°C high heat, and then gradually back down to near-ambient temperature, this temperature curve divides the process into four clearly defined stages.
Phase 1: Mesophilic (Heating) Phase
The mesophilic phase is the start-up period of aerobic fermentation, typically lasting 1-3 days. In this phase, the mesophilic microorganisms (bacteria, fungi, actinomycetes, etc.) naturally present in manure or organic waste become active. They use soluble and easily degradable organic matter (such as sugars, proteins, and starches) in the material as nutrients and energy sources, multiplying rapidly and releasing heat.
As microbial metabolic activity intensifies, the pile temperature gradually rises from ambient temperature to around 45°C.
Thanks to the excellent insulation performance of the tank body (Mingjia composting tanks feature a high-density polyurethane insulation layer), heat is effectively accumulated, and the temperature rises relatively quickly.
Phase 2: Thermophilic (High-Temperature) Phase
When the pile temperature rises above 45°C, the fermentation enters the thermophilic phase. This is the most critical stage of the entire aerobic fermentation process. As the temperature rises, mesophilic microorganisms are gradually inhibited or even die off, while thermophilic microorganisms (such as thermophilic Bacillus stearothermophilus) become the dominant population.
In the high-temperature environment of 60-70°C, thermophilic microorganisms efficiently decompose complex organic matter such as hemicellulose, cellulose, pectin substances, and some lignin. This phase typically lasts 5-7 days.
The core value of high temperature lies in sanitization – effectively killing pathogens, parasite eggs, and weed seeds. According to USEPA standards, maintaining pile temperature above 55°C for 3 days is sufficient to effectively kill pathogenic bacteria.
Phase 3: Cooling Phase
After the thermophilic phase, as easily degradable and moderately difficult organic matter is largely consumed, microbial activity gradually weakens, heat production decreases, and the pile temperature begins to naturally drop. When the temperature falls below 40°C, thermophilic microorganisms enter dormancy or die off, and mesophilic microorganisms regain dominance.
During the cooling phase, mesophilic microorganisms continue to decompose the remaining difficult-to-degrade organic matter. Microbial activity overall declines, and oxygen demand is greatly reduced.
This stage is a critical transition period from "active decomposition" to "approaching stabilization" of organic matter.
Phase 4: Maturation Phase
When the pile temperature drops to near-ambient levels (typically 30-40°C), the fermentation enters the final maturation phase. At this point, most microorganisms enter the endogenous respiration phase, leaving only some difficult-to-decompose organic matter and newly formed humus. The organic matter has basically stabilized, no longer generating significant heat, and oxygen demand is at its minimum.
Mature organic fertilizer has the following characteristics: dark brown or black-brown color, loose structure in powder or small granular form, no ammonia or sour smell but an earthy odor, and temperature stable near ambient.
The organic fertilizer discharged from Mingjia composting tanks has a moisture content of about 30%, and can be directly packaged and transported for sale as high-quality organic fertilizer or for field application.
How Mingjia Composting Tanks Ensure Efficient Four-Stage Operation
The smooth progression of the four stages of aerobic fermentation relies on precise process control. Mingjia's fully enclosed high-temperature aerobic composting tank provides optimal operating conditions for each stage through the following core technologies:
Intelligent Control System: A microcomputer monitors key parameters such as temperature, pressure, and oxygen content throughout the process, ensuring precise control of temperature and oxygen conditions at each stage.
Multi-point Bottom Oxygen Supply System: Equipped with ultra-energy-saving blowers (saving about 40% electricity), automatically adjusting oxygen supply intensity according to the oxygen demand of different stages.
High-density Polyurethane Insulation Layer: Effectively reduces heat loss, ensuring rapid start-up during the heating phase and temperature stability during the thermophilic phase.
Hydraulically Driven Mixing System: Forged integral ratchet drive ensures uniform oxygen contact with the material, preventing localized anaerobic conditions.
Waste Heat Recovery System: Returns heat from exhaust gas back to the tank for insulation, reducing energy consumption.
Summary
The four stages of aerobic fermentation – mesophilic (heating), thermophilic (high-temperature), cooling, and maturation – are a naturally evolving process driven by microorganisms and dominated by temperature. Each stage has its specific microbial populations, temperature ranges, and process control requirements.
Understanding this scientific logic is the foundation for optimizing fermentation processes and ensuring organic fertilizer quality.
Mingjia's fully enclosed high-temperature aerobic composting tank provides reliable support for the efficient operation of all four stages through core technologies including intelligent control, precise oxygen supply, efficient insulation, and waste heat recovery.
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