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Digital archive of theses discussed at the University of Pisa


Thesis etd-03082021-133800

Thesis type
Tesi di dottorato di ricerca
Thesis title
Modelling and Life Cycle Assessment of Power-to-Fuel production pathways: a comprehensive evaluation of different Carbon Capture Utilisation routes
Academic discipline
Course of study
tutor Prof. Desideri, Umberto
relatore Prof. Antonelli, Marco
relatore Prof.ssa Geldermann, Jutta
  • ammonia
  • Carbon Capture Utilization
  • energy storage
  • hydrogen
  • Life Cycle Assessment
  • methanol
  • Power-to-Fuel
  • synthetic natural gas
  • urea
Graduation session start date
Release date
Climate change concerns led many countries to limit carbon dioxide concentration in the atmosphere. The high penetration of renewable energy sources in the country energy mix for electricity production poses new challenge to keep the energy system functional and efficient. One of the most promising solutions to give resilience to the electric grid is to store electric energy. Among all the different kinds of energy storage, long-term (seasonal) storage is achievable by only some kinds of energy storages (i.e: mechanical and chemical). Besides a progressive shift of the power generation towards cleaner sources, another sector that needs an urgent decarbonization is the chemical industry. One promising option is to produce low impact chemicals by capturing carbon dioxide and transforming it into a valuable chemical product by using surplus electricity from the grid. In this way, the double function of decarbonizing the chemical industry and storing surplus electricity could be achieved. Though, the performances and the environmental impacts of the Carbon Capture Utilization are still largely untapped. In the present dissertation different Power-to-Fuel (PtF) production pathways are modelled and compared according to different performance indicators. The investigated chemicals are synthetic natural gas, methanol, ammonia and urea. After a state of the art about the status of PtF technologies, including techno-economical, environmental studies and a status of worldwide installed PtF plants, a detailed modelling of the investigated pathways is carried out and the plant performances are quantified in terms of efficiencies, specific consumption and environmental footprints according to several different impact categories. The impacts of producing the aforementioned synthetic chemicals are assessed with Life Cycle Assessment methodology, in a Cradle-to-Gate approach. A sensitivity analysis on the energy mix is carried out, using two 2030 forecasted energy mixes, and the use of electrolytic hydrogen in PtF chains is compared with the current conventional hydrogen production from cracking technologies. Another crucial parameter is the choice of the carbon dioxide source, therefore a sensitivity analysis on this is carried out, considering DAC and the most widespread European carbon dioxide emitting sources. Finally, the impact assessment of producing SNG from biomass and electrolytic hydrogen is performed by comparing six different layouts, and compared with the natural gas impacts. The analysis is carried out with different functional units and with different approaches to deal with multifunctionality. Some main findings of this work are that PtF technologies could serve as efficient storage technologies in support of decarbonization policies, under specific conditions. PtF plants can reach medium-high efficiencies of conversion, improvable with the development of more performing electrolyzers. To make synthetic fuels sustainable if compared to the fossil alternatives, the choice of the carbon dioxide source and of the electricity source is crucial.