Beyond Hydrogen Carriers: Global Green and Blue Ammonia Corridors for Industrial Integration and Trade

Hydrogen and ammonia are increasingly recognized as key molecular-energy carriers for decarbonizing hard-to-abate sectors, long-distance transport, maritime shipping, and seasonal energy storage. Although hydrogen offers high end-use efficiency and carbon-free energy utilization, its large-scale deployment remains constrained by storage, liquefaction, transport, and infrastructure challenges. Ammonia has consequently emerged as a promising hydrogen carrier because of its higher volumetric hydrogen density and compatibility with existing global storage and shipping infrastructure. However, ammonia systems also face important challenges related to toxicity, NOx emissions, cracking energy penalties, and lifecycle environmental uncertainty. This review provides a systems-level assessment of hydrogen and ammonia energy pathways, with an emphasis on production technologies, transport infrastructure, technoeconomic competitiveness, lifecycle greenhouse-gas emissions, industrial integration, and emerging molecular trade corridors. Particular attention is devoted to ammonia-corridor systems, hydrogen-backbone infrastructure, and integrated carbon-management networks within evolving molecular economies. The analysis shows that ammonia pathways are often more competitive for long-distance renewable-energy transport and international trade. In contrast, hydrogen systems remain better suited for localized industrial use and direct end-use applications. Nevertheless, the climate performance of blue hydrogen and blue ammonia remains highly sensitive to methane leakage, carbon-capture efficiency, and lifecycle-boundary assumptions. Overall, future hydrogen–ammonia deployment is expected to evolve through regionally differentiated, infrastructure-dependent transition pathways rather than a single, globally dominant energy architecture. Integrated molecular-energy systems combining renewable electricity, hydrogen networks, ammonia corridors, industrial clusters, and carbon-management infrastructure are likely to play a central role in future industrial decarbonization strategies.