An overview of process monitoring for anaerobic digestion

Anaerobic digestion (AD) is a traditional process that not only manages different sources of organic waste but also generates renewable energy (biomethane) at the same time. However, AD relies on the cooperation of certain microbial communities and is, therefore, vulnerable to process disturbances that may affect biogas production and methane yield. In this context, process monitoring has been receiving attention as a strategy for achieving a stable process and ensuring a high yield of biogas. This review was undertaken to address the recent progress related to contemporary techniques deployed for real-time monitoring of the AD process at different scales. It also points out the necessity of choosing appropriate early-warning indicators and proper monitoring biosystems to achieve accurate information on the bioprocess. Nonetheless, the implementation of online monitoring techniques has been restricted due to its high-cost, which limits its industrial application. On this premise of rigid cost control, further studies are required to make AD real-time monitoring more technically and economically sustainable.