A critical review of ammonia recovery from anaerobic digestate of organic wastes via stripping

Anaerobic digestion is a well-established technology that valorises organic wastes to produce renewable energy as biogas. The ammonia released during this process can be inhibitory if it exceeds a threshold concentration. Additionally, ammonia is a harmful environmental pollutant and also a renewable source of energy, thus establishing a need for the recovery of ammonia. Gas-liquid stripping is one such widely researched technology to recover ammonia from wastewater. However, there have not been any reviews focusing solely on the application of stripping to recover ammonia from the anaerobic digestate of organic wastes. This study reviews the current state of research in this field, focusing on the factors affecting the ammonia recovery, stripping column designs and linking of an anaerobic digester to a stripping column. An overview of the work done on the modelling of the ammonia stripping from digestate is also included. This review offers a direction for further research in this field; i.e., experimental and modelling studies on i) the effect of digestate composition on ammonia recovery and ii) the effect of stripping gas on ammonia removal.

Automated summary

Anaerobic digestion is a mature technology that converts organic waste into biogas, but the released ammonia may have inhibitory effects, necessitating its recovery. Gas-liquid stripping is a technology to recover ammonia, but research on its application to anaerobic digestate of organic wastes is limited. Further research could focus on the effect of digestate composition on ammonia recovery and the impact of stripping gas on ammonia removal.