Hydrogen as a sustainable transportation fuel

This review examines the potential direct and indirect (synthetic fuels) uses of hydrogen in road, rail, air, and marine transportation. Key physical properties of hydrogen (e.g., energy density) are presented and contrasted against conventional fuels. The costs and emissions of current and future hydrogen production methods are characterized, and the challenges of transporting, storing, distributing, and dispensing hydrogen are highlighted. The sustainability of hydrogen use is evaluated in terms of CO 2 and other air pollutant emissions, energy efficiency and intensity, critical material use, and water consumption. Electrification is much more energy efficient than using hydrogen in transportation. Hydrogen should be used strategically where electrification is impractical due to range, refueling times, or energy storage requirements. Electrification is already well advanced, making hydrogen unlikely to play a significant role in the light-duty road sector. Hydrogen can play a role in long-distance rail and heavy-duty road transportation, where electrification is problematic. Electrification is impractical for deep ocean shipping and aviation due to volume and weight constraints (except for ranges below approximately 200 miles). Hydrogen can be used, either directly or indirectly (in e-fuels), to fully decarbonize these sectors. Currently, the high costs of clean hydrogen production, storage, and distribution make it prohibitive for transportation. Major reductions in these hydrogen infrastructure costs, the cost of e-fuel synthesis, or both are needed to make hydrogen competitive with other fuel options. Strong policy measures such as the Bipartisan Infrastructure Law and the Inflation Reduction Act are funding R&D and technology demonstration to support this goal. • Hydrogen is unlikely to play a significant role in the light-duty road sector. • Hydrogen system energy intensity for freight spans four orders from ships to aircraft. • System energy intensities for passenger transportation are more similar across modes. • Cost reductions (5–10 fold) in H 2 production, distribution, & storage are needed. • Technologies to mitigate hydrogen leakage and transfer losses need to be developed.