Life cycle assessment of hydrogen delivery pathways: a review

• LNH 3 is most efficient for long-distance hydrogen transport. • LH 2 has lower emissions if powered by renewable electricity. • LOHCs offer safe storage but need high energy for conversion. • LCA results vary due to inconsistent boundaries and data sources. • Harmonized LCA methods needed for reliable hydrogen policy. As an adaptable energy carrier, hydrogen is capable of playing a crucial role in the world’s low-carbon fuel future. Its environmental benefits, high efficiency, and potential to unify the power and transportation sectors would facilitate clean, flexible, and secure energy. However, a sustainable hydrogen supply chain not only requires robust infrastructure deployment and supportive government policies but also depends heavily on the choice of hydrogen production pathways, including the feedstock and energy sources used, processes for converting hydrogen into hydrogen carriers, and storage and transportation options. Life cycle assessment (LCA) is an essential method of identifying environmentally sustainable hydrogen delivery pathways and accelerating the global development of the hydrogen economy. This paper provides a systematic review of LCA studies for hydrogen delivery pathways, focusing on hydrogen carriers, specifically liquid hydrogen (LH 2 ), liquid ammonia (LNH 3 ), and liquid organic hydrogen carriers (LOHCs). Our review paper shows that LCA results regarding life cycle carbon emissions vary widely due to differences in system boundaries, functional units, and the type of life cycle inventory sources, underscoring the need for standardization and transparency. Advancing hydrogen infrastructure will require not only technical improvements in hydrogen carriers’ production efficiency and transportation protocols, but also harmonized LCA methodologies to inform policy, certification, and market decisions for deep decarbonization.