The composting process is typically divided into four stages: mesophilic (warm-up), thermophilic (high-temperature), cooling, and maturation. Below are the temperature ranges and microbial activity characteristics for each stage:

1. Mesophilic Stage (Warm-Up/Heat Generation Phase)

• Temperature Range: 15°C–45°C
• Microbial Activity:
  • Dominated by mesophilic microorganisms (bacteria, fungi, actinomycetes), which decompose soluble organic matter (e.g., sugars, starches).
  • Rapid microbial metabolism generates heat, causing stack temperatures to rise quickly.
• Key Points:
  • At 25°C, mesophilic bacteria proliferate, raising temperatures to 40°C–45°C within 20 hours.
  • Bacteria target water-soluble monosaccharides, while actinomycetes and fungi break down cellulose and hemicellulose.

2. Thermophilic Stage (High-Temperature Phase)

• Temperature Range: Above 45°C (optimal: 55°C–60°C)
• Microbial Activity:
  • Mesophiles are suppressed, and thermophiles (e.g., Bacillus, actinomycetes) dominate.
  • Complex organic matter (hemicellulose, cellulose, proteins) is decomposed, forming humus.
  • Thermophilic populations progress through logarithmic growth, decelerated growth, and endogenous respiration phases.
• Key Points:
  • At 60°C, fungal activity ceases; above 70°C, thermophiles enter dormancy or die.
  • Sustaining temperatures >55°C for 5+ days kills pathogens, parasite eggs, and weed seeds.
  • Excessive heat (>65°C) inhibits microbial activity, requiring turning or aeration to cool.

3. Cooling Stage (Early Maturation Phase)

• Temperature Range: Drops below 50°C
• Microbial Activity:
  • Mesophiles reactivate, decomposing residual recalcitrant organic matter (e.g., lignin).
  • Humus content increases, enhancing compost stability.
• Key Points:
  • Reduced microbial activity lowers heat generation, causing natural temperature decline.
  • Oxygen demand decreases, moisture content drops, and stack porosity improves, facilitating oxygen diffusion.

4. Maturation Stage (Post-Fermentation Phase)

• Temperature Range: Approaches ambient temperature
• Microbial Activity:
  • Mesophiles continue breaking down residual organic matter, further stabilizing humus.
  • Microbial diversity and abundance decline, with reduced metabolic activity.
• Key Points:
  • The compost stabilizes, with enriched nutrient content (especially nitrogen).
  • Mature compost appears dark brown, loose in texture, odorless, and non-attractive to flies.

Summary of Stage Characteristics

Management Guidelines

• Temperature Control: Maintain 55°C–60°C in the thermophilic phase to eliminate pathogens; avoid >75°C to prevent excessive organic matter loss.
• Aeration Adjustment: Increase ventilation during warm-up, moderate aeration in high-temperature phases to cool, and reduce aeration during cooling to retain nutrients.
• Turning Operations: Turn stacks post-thermophilic phase to enhance oxygen supply and accelerate maturation.
• pH Regulation: No neutralization required; pH self-adjusts to 5.5–9.0.
• C/N Ratio: Optimal range is 20:1–30:1 (anaerobic fermentation) or 75:1–150:1 (solid organic composting).

This translation maintains technical accuracy while adapting terminology and structure for an English-speaking audience in composting or environmental science contexts.