Life Cycle Assessment of hydrogen for mobility options and energy systems based on carbon neutral fuels

Hydrogen produced from renewable or low-carbon energy sources is set to play a crucial role in the decarbonisation of energy systems. The use of hydrogen as a clean fuel, especially for the transport sector, has been under study for decades. In recent years, there has been a renewed confidence in technologies based on the use of hydrogen produced from renewable energy sources. However, the launch of a hydrogen economy still presents significant barriers that need to be overcome. Beyond the need to start from scratch a massive production of renewable-based hydrogen, there is also the need to solve other traditional problems related to the transport, distribution, storage and final use of hydrogen. In this context, therefore, it is essential to find smart and effective strategies that could facilitate this transition to clean hydrogen energy systems. Within the framework of this doctoral thesis, various strategies are presented aimed at circumventing some barriers and at favouring and speed-up the advent of a hydrogen economy. One of these possibilities lies in the production of carbon-neutral and synthetic renewable fuels, by combining renewable hydrogen with a carbon source. Regarding hydrogen vehicles instead, a part from the well-known fuel cells, several other technologies are conceivable. Moreover, being hydrogen an energy carrier which does not involve particular environmental criticalities during its use, it is essential to carefully check the environmental suitability of hydrogen-based fuels and technologies under a full life-cycle perspective. Three research lines were mainly conducted: i) proposal of innovative short-term national strategies to allow a faster implementation of renewable hydrogen in road transport, through assessment of the environmental suitability of renewable hydrogen as a fuel for sustainable mobility. Different technical vehicle and fleet options were evaluated; (ii) evaluation of the technical and environmental potentialities of systems for the production of carbon-neutral fuels (such as renewable-based substitute natural gas) and possible co-production of electricity, starting from renewable energy sources and biomass; (iii) evaluation of the life-cycle environmental performance of renewable hydrogen production systems (mainly through electrolysis) and environmental footprint of the produced hydrogen. Overall, this doctoral thesis provided advances and developments on sustainable energy systems and alternative vehicles based on hydrogen and carbon-neutral fuels, both from an energy and an environmental life-cycle perspective, paving the way towards a faster implementation of hydrogen in the current energy sector.