Anaerobic digestion: A review on process monitoring

Biogas plants can effectively treat organic wastes from various sources and recover energy from biomass for commercial use. However, anaerobic digestion (AD) can suffer from process instability, which can affect efficiency of biogas production. Process monitoring can be used to ensure stable and efficient biogas production process. In recent years, researchers have paid increasing attention to process monitoring as a means of stabilizing anaerobic reactors and ensuring high biogas production. This review of process monitoring of AD focuses on recent progress related to effective early-warning indicators and robust, applicable monitoring methods. A review of the literature revealed that explorations of process monitoring parameters have mainly focused on the metabolic process of AD itself, while the importance of monitoring the feeding substrate as a means of optimizing process stability has not been valued sufficiently. In addition, the application of robust online monitoring methods developed in the laboratory to real-world applications in biogas plants has been limited by high costs. In the future, on the premise of strict cost control, better understanding of the mechanisms underlying AD instability and increased attention focused on online monitoring of the feeding substrate will facilitate optimization of the production process at biogas plants to achieve efficient and stable production.