Ammonia recovery from waste streams: Energy efficiency and performance of microbial electrochemical system and electrochemical system

Nutrient recovery from waste streams, particularly digestate from anaerobic digestion, represents a promising strategy for sustainable waste management and circular economy practices. This study evaluated the performance of electrochemical (ES) and Microbial electrochemical systems (MES) for ammonia recovery from digestate under varying voltages. Energy consumption, and natural pH increase in catholyte were investigated for increased recovery efficiency. The results demonstrate that MES and ES exhibited similar recovery rates, with ammonia recovery reaching approx. 49 % at 1.2 V, while at lower energy efficiency MES outperformed ES. At '0' voltage, MES achieved a baseline recovery of 31.85 %, significantly higher than ES (13.25 %), highlighting the contribution of microbial electrochemical activity in driving nutrient recovery with minimal energy input. MES exhibited remarkably lower energy consumption, requiring nine-fold less energy than ES at low applied voltages, owing to the synergistic effects of microbial activity and bioelectricity generation. Moreover, MES minimized ammonium transport losses and showed better stability in cathodic pH variations, favouring long-term operational viability. The findings in MES as a more sustainable alternative for ammonia recovery, emphasizing its potential to global carbon neutrality and operational costs in nutrient recycling processes.