Liquid Hydrogen: A Mirage or Potent Solution for Aviation's Climate Woes?

The aviation industry faces a formidable challenge to cap its climate impact in the face of continued growth in passengers and freight. Liquid hydrogen (LH 2 ) is one of the alternative jet fuels under consideration as it does not produce carbon dioxide upon combustion. We conducted a well-to-wake life cycle assessment of CO 2 emissions and non-CO 2 climate change impacts per passenger-distance for 17 different hydrogen production routes, as well as conventional jet fuel and biofuels. Six other environmental and health impact categories were also considered. The Boeing 787-800 was used as the reference aircraft, and a range of flight distances were explored. Contrail cirrus contributes around 81 ± 31% of the combustion climate impacts for LH 2 , compared to 32 ± 7% for conventional jet fuel, showing that research is needed to reduce uncertainty in the case of LH 2 . The life cycle impacts of the two dominant commercial LH 2 pathways are on average 8 and 121% larger than conventional jet fuel. Some novel LH 2 pathways do show considerable potential for life cycle climate impact reductions versus conventional fuel (up to -205 ± 78%). LH 2 from renewable energy is not climate neutral, though, at best -67 ± 10% compared to conventional over the life cycle.