Converting Waste Tires into Blue Ammonia: Safe and Sustainable Process Design, Multiobjective Optimization and Comprehensive Assessment

Abstract Ammonia synthesis based on steam methane reforming (SMR) is characterized by intensive energy consumption and high carbon emissions. To address these limitations, novel processes integrating gasification and carbon capture technologies were proposed for converting waste tires into blue ammonia. Detailed safety, techno-economic, and life cycle assessments were conducted to evaluate comprehensive performance. Machine learning-driven multiobjective operation optimization was carried out for reducing levelized cost of ammonia (LCOA) while enhancing safety and sustainability scores based on safe-and-sustainable-by-design framework. Our results highlight the critical role of artificial neural networks in achieving efficient optimization. Additionally, the quantitative impacts of integrating various renewable energy sources were investigated. The results showed the conventional gasification (CG) integrating methyldiethanolamine (MDEA)-based carbon capture alternative achieved the optimal LCOA at 358.1 $/ton in current electricity scenario. A peak environmental sustainability score of 0.443 was achieved, outperforming traditional SMR integrating MDEA-based carbon capture pathway by 13.04%. The safest process is CG integrating monoethanolamine-based carbon capture. Under the renewable scenario, the LCA results highlighted the critical role of renewable energy integration in enhancing the environmental sustainability of waste tires-to-ammonia processes, especially achieving a 0.344 increase in environmental sustainability score with onshore wind electricity at a lower LCOA of 406.0 $/ton in plasma gasification integrating MDEA-based alternative.