Toward sustainable ammonia: A techno-economic and environmental assessment of emerging electrochemical ammonia synthesis pathways

Abstract

This study conducts a comprehensive techno-economic and environmental assessment of three emerging electrochemical ammonia (NH3) synthesis pathways: nitrogen reduction (N2RR), lithium-mediated nitrogen reduction (Li-NRR), and nitrate reduction (NO3RR). Based on experimental system-level data, we quantify the levelized cost of ammonia (LCOA) and global warming impact (GWI) for each pathway under future grid scenarios. Of the assessed routes, NO3RR demonstrates the most favorable performance (LCOA: $0.84/kg; GWI: similar to 2 kg CO(2)eq/kg NH3), particularly when using wastewater-derived nitrate. Li-NRR moderate economic feasibility ($1.13/kg), enabled by gas-phase NH3 separation, although it remains sensitive to the hydrogen source. In contrast, N2RR represents the most direct route for the production of NH3 from N-2 but requires major advances in catalyst selectivity and current density to reduce the LCOA (>$1.7/kg). Sensitivity analysis reveals bottlenecks that must be addressed for electrochemical NH3 synthesis to become a viable alternative to the Haber-Bosch process, including catalytic and system-level limitations for N2RR, energy efficiency and hydrogen sourcing for Li-NRR, and sustainable nitrate supply chains for NO3RR. These findings provide insights for the development of research and deployment strategies for economically viable and climate-competitive electrochemical NH3 production.