Towards effective management of digester dysfunction during anaerobic treatment processes

Highlights: • Anaerobic digester operation can be effectively monitored with VFA/alkalinity. • Volumetric loading rate or VFA saturation provide information on the digester imbalance. • Conductive materials reduce volatile acid build-up in digesters. • Multi-stage digesters and super-high-rate systems accommodate higher organic loading rates. • Biogas production can be optimized via statistical modelling. -- Abstract: Anaerobic digestion (AD) of organic substrates for biogas production is constantly challenged by some critical factors (ammonia inhibition, hydrogen partial pressure and volatile fatty acid accumulation) which result in digester imbalance or failure. This review was undertaken to address how these critical perturbations have challenged AD-derived bioenergy. The key advances (e.g., early warning indicators) for the detection and informing the operators of the digester imbalance such as VFA/alkalinity measurements, e-nose (metal oxide), biogas isotopic labelling and volumetric loading rate and/or VFA saturation estimation were addressed. The novel strategies towards the alleviation of the perturbation causing anaerobic digester dysfunction such as use of multi-stage digesters, use of super high rate systems, introduction of pure microbial cultures and deployment of direct interspecies electron transfer (conductive materials) and statistical modelling are also presented. While some of these approaches are promising in real applications (especially those that are currently at pilot-scale operation), others have been attempted theoretically or shown no recorded success. Considering the varying success in mitigating these challenges, the practical implications of the current study and the future prospects were highlighted.