A Dynamic Multiparameter Stability Index for Industrial Anaerobic Digester Performance Monitoring

Anaerobic digestion (AD) is a widely used technology for converting organic waste into biogas while supporting sustainable waste management and the circular economy. However, maintaining stable digester performance remains challenging because the process depends on complex interactions among feedstock characteristics, microbial activity, and operating conditions. Conventional monitoring parameters, such as pH, volatile fatty acids (VFAs), alkalinity, methane content, ammonia concentration, and organic loading rate, provide useful information but often fail to capture the overall health of the digestion process. This review introduces the Dynamic Multiparameter Stability Index (DMSI), an integrated framework that combines physicochemical, operational, and biological indicators into a single stability index for real-time process assessment and early detection of instability. The framework includes key parameters such as VFAs, the VFA-to-alkalinity ratio, methane concentration, biogas production rate, ammonia levels, hydraulic retention time, and microbial stability indicators. It also discusses feedstock-specific monitoring strategies for food waste, press mud, bagasse, hybrid Napier grass, water hyacinth, and co-digestion systems. The proposed DMSI offers a practical tool to improve process stability, enhance methane production, and support the integration of artificial intelligence and Industry 4.0 technologies in future smart biogas plants.