Comparative life cycle assessment of carbon-free ammonia as fuel for power generation based on the perspective of supply chains

In recent years, there has been a surge in ammonia demand due to growing interest in carbon-free fuel for decarbonization. Thus, it is crucial to identify the methods to fulfill the required demand, particularly for countries with resource scarcity or lacking well-established production infrastructure. The present study compares environmental impact analysis between domestic ammonia production and import ammonia for these countries by using life cycle assessment (LCA) methodology. In these ammonia supply paths, five different production ways were applied: gray (conventional Haber-Bosch process), blue (with carbon capture and storage), green (wind, solar, and nuclear powered water electrolysis with Haber-Bosch process). The assessment showed highest global warming potential (GWP) value at 2.64 ton CO₂-eq/ton NH₃ for imported gray while domestic nuclear-driven ammonia had the lowest value at 0.81 ton CO₂-eq/ton NH₃. In addition, contrary to expectations, the human and environment impact of green ammonias were all higher than gray and blue ammonia due to the production of raw materials. This means that environmental improvements of related production process are crucial in preparation for the coming new energy regime, which then lead to the production of environmentally friendly ammonia. Lastly, these results offer valuable guideline for future energy strategy planning.