Green hydrogen and alternative fuels for climate mitigation: a cross-sectoral techno-economic and deployment perspective

Green hydrogen and its low-carbon derivatives are increasingly considered for decarbonising sectors in which direct electrification is technically constrained or cannot replace a required molecular feedstock. This review examines the technical, techno-economic, environmental, infrastructure, and deployment conditions that determine where green hydrogen and hydrogen-derived alternative fuels can provide effective climate-mitigation pathways across major end-use sectors. Global hydrogen demand reached approximately 100 Mt in 2024, while low-emissions hydrogen accounted for less than 1% of supply. Announced projects could provide approximately 37 Mtpa by 2030, yet only about 4.2 Mtpa has reached operation or final investment decision, indicating a substantial project-bankability gap. The synthesis shows that electricity cost, utilisation, offtake certainty, infrastructure, regulatory eligibility, renewable-resource availability, and water management govern hydrogen deployment. Conversion to ammonia, methanol, and synthetic hydrocarbons introduces additional energy losses but can provide storage, transport, and infrastructure advantages in shipping and aviation.