Life cycle assessment of an innovative ammonia production process via electrochemical reduction of nitrates in aqueous solution

Ammonia is traditionally produced using the Haber-Bosch process, which requires high temperatures and pressures. Efforts are now focused on finding ways to synthesize NH3 under milder conditions, and the electrochemical nitrate reduction reaction (E-NO3RR) is a promising approach, allowing to produce ammonia starting from waste flows rich in nitrate ions. The aim of this study is to conduct the life cycle assessment (LCA) of the technology at a laboratory scale, to identify its environmental hotspots and to evaluate the flows of critical raw materials (CRMs) and the cost of externalities (CoE) of the process, under a safe and sustainable by design (SSbD) perspective. Results highlight polytetrafluoroethylene (PTFE) and iridium oxide used within the flow cell manufacturing as the most impactful materials, while the electricity consumed to conduct the synthesis is the highest overall contributor to the impacts during the NH3 synthesis. Furthermore, the approach allows to individuate the flow cell as the highest contributor to the consumption of CRMs and the electricity usage as the most impactful process in terms of CoE at laboratory scale, providing insightful information to the developers towards a more sustainable and competitive scale-up of the technology.