Composting: Industrial Processes, Factors, and Stages

Industrial Composting Processes

Compost is created through a biological process, relying on aerobic fermentation (with air). This technique ensures hygienic processing of organic waste into a homogeneous substance easily assimilated by the soil. The process involves a microbial population, including bacteria, actinomycetes, and fungi (responsible for 95% of the activity), as well as algae, protozoa, and cyanophytes.

Suitable Organic Materials for Composting

• Plants from the garden or orchard
• Adventitious herbs or "weeds" (before they seed)
• Poultry manure and bedding
• Lawn clippings (in thin, dried layers)
• Organic food remains
• Napkins and tissues (unprinted and uncolored)
• Haircuts (undyed)
• Raw wool or old mattresses (in small, mixed layers)
• Wine, vinegar, beer, spirits, edible oils, and fats (sparsely scattered in small quantities)

Critical Factors in Compost Production

Critical factors include:

• Temperature (°C)
• pH
• Humidity
• Carbon/Nitrogen Ratio
• Aeration
• Particle Size
• Time
• Stabilization Period

Stages of Composting

Composting involves four main operations:

1. Waste Reception

2. Selection and Conditioning

This phase involves initial selection and cleaning of raw materials, followed by crushing and conditioning to increase the surface area for microbial action.

3. Composting Phase

The composting process is divided into four periods based on temperature changes:

Mesophilic Phase

The compost mass is at room temperature, and mesophilic microorganisms multiply rapidly. Their metabolic activity raises the temperature and produces organic acids, lowering the pH.

Thermophilic Phase

When the temperature reaches 40°C, thermophilic microorganisms transform nitrogen into ammonia, raising the pH. At 60°C, fungi disappear, and thermophilic bacteria and sporogenous actinomycetes appear. These organisms break down waxes, proteins, and hemicellulose.

Cooling Phase

When the temperature drops below 60°C, thermophilic fungi reappear and break down cellulose. As the temperature lowers to 40°C, mesophilic organisms resume activity, and the pH drops slightly.

Maturation Phase

This phase requires months at room temperature, during which secondary reactions of condensation and polymerization of humus occur.

4. Final Treatment and Storage

Mature compost undergoes grinding and sieving to reduce particle size, making it easier to store and package.