Can existing or future pathways reduce green ammonia production costs?

Many scenarios for the energy transition consider green ammonia. The technologically most mature production process combines water electrolysis and Haber-Bosch process (EHB). Its costs are dominated by electrolyzer investment costs and electricity. Emerging pathways researched in academia, start-ups, and industry try to reduce costs by changing sub-processes and chemistry. However, it remains unclear which pathways have the potential to outperform EHB, if any. We assess relevant emerging pathways, compare to EHB in terms of costs and energy demand, and derive performance targets. Many pathways investigated in the literature, such as metalmediated electrolysis, have theoretical minimal energy demands well above the actual energy demand of EHB; consequently, they cannot produce ammonia at competitive costs due to the high influence of electricity costs. Any novel pathway must employ simple and energy-effective chemistry to substantially reduce costs. Identified performance targets are applicable to novel pathways and can guide research, industry, and policy makers.