Aerobic Annealing Process and Factors Affecting Aerobic Annealing

How does aerobic incubation take place?

Stage 1: Adaptation

Temperatures rise rapidly up to 65-70⁰C during the first few days. First, thermophiles proliferate rapidly on available sugars and amino acids. They generate heat by their own metabolism and increase their temperature to the point where their activities become inhibited.

Stage 2: Growth

This is the period when bacteria grow the most. Some thermophilic fungi and some thermophilic bacteria (optimal temperature range: 50-70⁰C or lower) continue the process, raising the temperature of the material to 75-80⁰C or higher. This peak heating period is important to the quality of the compost because heat destroys pathogens and weed seeds.

Stage 3: Ripening

Eventually, the temperature drops below ambient temperature. By the time composting is completed, the compost will become more uniform and less biologically active even though thermophilic organisms regenerate the compost. The finished product has a color ranging from gray brown to black. The particles decrease in size, becoming consistent and have a soil-like texture. During this process, the amount of humus increases, the ratio of carbon to nitrogen (C:N) decreases, the pH neutralizes, the exchange capacity of the material increases.

Factors affecting the aerobic incubation process

Oxi

Humidity

Moisture is necessary to support the metabolic activity of microorganisms. The compost material should maintain a moisture content of 40 – 65%. Where the compost pile is too dry, the composting process is slower. If humidity exceeds 65% anaerobic conditions will develop. In practice, incubation should start at 50-60% humidity, finishing at around 30%.

Temperature

The analysis process includes two scopes. While the ideal temperature for the initial stage is 20-45⁰C, in subsequent stages when thermophilic microorganisms take over, a temperature range of 50-70⁰C may be ideal.Extremely high in temperature clumping process and is a sign of strong microbial dynamics. Pathogens are usually destroyed at 55⁰C and above, while the critical point that can eliminate weed seeds is 62⁰C.Reverse can be used to adjust temperature.

pH

Although the natural buffering effect of composting has the effect of accepting material over a wide range of pH levels, pH levels should not exceed 8. At higher pH levels, more ammonia gas is produced and can can be lost to the atmosphere.

Nutrients

Microorganisms require C, N, phosphorus (P) and potassium (K) as primary nutrients. Of particular importance is the C:N ratio of the feedstock.
The optimal C:N ratio of raw materials is between 25:1 and 30:1.Where the C:N ratio is higher than 40:1, microbial growth is limited, resulting in longer composting times.A C:N ratio less than 20:1 leads to overuse of N, and the excess can be lost to the atmosphere as ammonia or nitrogen oxides and cause odor problems. The final product has a C:N ratio between 10:1 and 15:1.