Optimising fuel supply chains within planetary boundaries: A case study of hydrogen for road transport in the UK

The world-wide sustainability implications of transport technologies remain unclear because their assessment often relies on metrics that are hard to interpret from a global perspective. To contribute to filling this gap, here we apply the concept of planetary boundaries (PBs), i.e., a set of biophysical limits critical for operating the planet safely, to address the optimal design of sustainable fuel supply chains (SCs) focusing on hydrogen for vehicle use. By incorporating PBs into a mixed-integer linear programming model (MILP), we identify SC configurations that satisfy a given transport demand while minimising the PBs transgression level, i.e., while reducing the risk of surpassing the ecological capacity of the Earth. On applying this methodology to the UK, we find that the current fossil-based sector is unsustainable as it transgresses the energy imbalance, CO2 concentration, and ocean acidification PBs heavily, i.e., five to 55-fold depending on the downscale principle. The move to hydrogen would help to reduce current transgression levels substantially, i.e., reductions of 9–86% depending on the case. However, it would be insufficient to operate entirely within all the PBs concurrently. The minimum impact SCs would produce hydrogen via water electrolysis powered by wind and nuclear energy and store it in compressed form followed by distribution via rail, which would require as much as 37TWh of electricity per year. Our work unfolds new avenues for the incorporation of PBs in the assessment and optimisation of energy systems to arrive at sustainable solutions that are entirely consistent with the carrying capacity of the planet.