A review of high-solid anaerobic digestion (HSAD): From transport phenomena to process design.

High-solid anaerobic digestion (HSAD) is an attractive organic waste disposal method for bioenergy recovery and climate change mitigation. The development of HSAD is facing several challenges such as low biogas and methane yields, low reaction rates, and ease of process inhibition due to low mass diffusion and mixing limitations of the process. Therefore, the recent progress in HSAD is critically reviewed with a focus on transport phenomena and process modelling. Specifically, the work discusses hydrodynamic phenomena, biokinetic mechanisms, HSAD-specific reactor simulations, state-of-the-art multi-stage reactor designs, industrial ramifications, and key parameters that enable sustained operation of HSAD processes. Further research on novel materials such as bio-additives, adsorbents, and surfactants can augment HSAD process efficiency, while ensuring the stability. Additionally, a generic simulation tool is of urgent need to enable a better coupling between biokinetic phenomena, hydrodynamics, and heat and mass transfer that would warrant HSAD process scale-up. • HSAD suffers from limited heat and mass transfer due to moisture deficit. • Reactor designs and operational strategies can mitigate potential challenges. • HSAD reactor control algorithm must be informed with feedstock properties. • Integrating biokinetic models, CFD and ML will improve process simulation. • Novel engineered-materials can improve transport characteristics of HSAD process. [ABSTRACT FROM AUTHOR]