The role of hydrogen in heavy transport to operate within planetary boundaries.

Green hydrogen, , produced from renewable resources, is attracting attention as an alternative fuel for the future of heavy road transport and long-distance driving. However, the benefits linked to zero pollution at the usage stage can be overturned when considering the upstream processes linked to the raw materials and energy requirements. To better understand the global environmental implications of fuelling heavy transport with hydrogen, we quantified the environmental impacts over the full life cycle of hydrogen use in the context of the Planetary Boundaries (PBs). The scenarios assessed cover hydrogen from biomass gasification (with and without carbon capture and storage [CCS]) and electrolysis powered by wind, solar, bioenergy with CCS, nuclear, and grid electricity. Our results show that the current diesel-based-heavy transport sector is unsustainable due to the transgression of the climate change-related PBs (exceeding standalone by two times the global climate-change budget). Hydrogen-fuelled heavy transport would reduce the global pressure on the climate change-related PBs helping the transport sector to stay within the safe operating space (, below one-third of the global ecological budget in all the scenarios analysed). However, the best scenarios in terms of climate change, which are biomass-based, would shift burdens to the biosphere integrity and nitrogen flow PBs. In contrast, burden shifting in the electrolytic scenarios would be negligible, with hydrogen from wind electricity emerging as an appealing technology despite attaining higher carbon emissions than the biomass routes.