An evaluation of substrate degradation patterns in the composting process. Part 1: profiles at constant temperature

Area of Science:

• Environmental Science
• Biotechnology
• Mathematical Modeling

Background:

• Substrate degradation is a key process in composting.
• Accurate modeling of degradation kinetics is essential for optimizing composting processes.
• Existing models may not fully capture the complexity of constant temperature degradation.

Purpose of the Study:

• To evaluate the effectiveness of three mathematical models (single exponential, double exponential, and non-logarithmic Gompertz) in describing constant temperature substrate degradation profiles.
• To analyze the shapes and patterns of 32 composting substrate degradation profiles from existing literature.
• To assess the goodness of fit for each model against empirical data.

Main Methods:

• Collected and analyzed 32 substrate degradation profiles from composting literature.
• Applied single exponential, double exponential, and non-logarithmic Gompertz models to the data.
• Assessed model performance using a normalized error function and a five-category rating scale (excellent to poor).

Main Results:

• Degradation profiles were predominantly sigmoidal or multi-phase; few were convex.
• 26 out of 32 profiles were poorly described by the tested models.
• No excellent fits were achieved; only a few good fits were observed for each model.
• Most fits were rated as moderate to poor.

Conclusions:

• The use of single exponential, double exponential, or non-logarithmic Gompertz models to describe constant temperature substrate degradation profiles is currently limited.
• Further research is needed to develop standard procedures and simulated composting mixtures.
• Generation of more comprehensive long-term degradation data under controlled conditions is recommended.