A Comparative Life Cycle Assessment on Nuclear-Based Clean Ammonia Synthesis Methods

摘要

This paper evaluates the impacts of nuclear ammonia synthesis options on the environment through the life cycle assessment (LCA) technique. Ammonia is synthesized via the mature Haber-Bosch technique that combines hydrogen and nitrogen with 3:1 ratio to yield ammonia. For hydrogen production from water, five different hydrogen production methods are used, namely, conventional electrolysis (CE), high-temperature electrolysis (HTE), and 3-, 4-, and 5-step Cu-Cl cycles. The nitrogen required for ammonia synthesis is extracted from the air by the cryogenic air separation technique. The thermal and electrical energy need of production processes is supplied from a pressurized water reactor type nuclear power plant (NPP). The simapro software is utilized for LCA in the present study. The environmental impacts of nuclear ammonia are investigated through five impact categories, namely, abiotic depletion potential, acidification potential, global warming potential (GWP), ozone depletion potential, and human toxicity potential. According to LCA results, ammonia synthesis via HTE corresponds to the lowest environmental impact in all selected impact categories. Furthermore, the GWP for ammonia production via HTE is 0.1832 kg CO_2 eq/kg ammonia, followed by CE (0.2240 kg CO_2 eq/kg ammonia), 4-step Cu-Cl (0.3113 kg CO_2 eq/kg ammonia), 3-step Cu-Cl (0.3323 kg CO_2 eq/kg ammonia), and 5-step Cu-Cl (0.3370 kg CO_2 eq/kg ammonia).