A mini-review on performance metrics for electrochemically mediated ammonia recovery from wastewater†

Ammonia recovery from various waste streams offers a promising pathway to move towards a more sustainable fertilizer production while minimizing the heavy reliance on fossil fuels. Several electrochemical methods have demonstrated promise over existing biological and physicochemical approaches due to the ability to separate and convert ammonium to ammonia via electrochemically mediated processes. However, the performance is generally standardized only to energy consumption that may overlook the effectiveness of ammonia recovery, thereby leading to an incomplete assessment. In this mini-review, we created a new plot to compare energy consumption and productivity as key performance metrics. The productivity was calculated using the molar flux of ammonium N separated from wastewater, which was then normalized by the mass of membranes as the key active component as well as to grasp the key operating condition and system parameter. By analyzing a comprehensive set of the literature data on the energy–productivity plot, we aimed to provide valuable insights into the current status and future directions of electrochemically mediated ammonia recovery from wastewater.