The decarbonisation of the transport sector is key to meeting climate goals, especially those related to sustainable development. In this context, under the premise that liquid fuels are and will continue to be the primary source of energy worldwide in the coming decades, so-called e-fuels, produced from H2O, CO2 and renewable energy, represent a promising alternative due to their compatibility with existing infrastructures and their low carbon footprint compared to conventional fuels. However, their full economic and environmental performance remains unclear, as most studies in this area focus only on the economic dimension, neglecting the environmental aspect and the economic costs it entails.
This thesis, therefore, explores the economic and environmental performance of carbon- and nitrogen-based e-fuels for road and air transport, which are obtained via electrolysis and co-electrolysis-based processes powered by renewable solar and wind electricity. Since renewable solar and wind energy availability varies significantly with location and timeframe, e-fuel production is assessed in several locations from different sources of CO2, N2 and green H2. Here, the sustainability of production processes is critically assessed by combining a palette of tools encompassing process simulation, optimisation, cost evaluation, life-cycle assessment (LCA) explicitly accounting for externalities, and uncertainty analysis.
The results show that, with current technology and under current market conditions, e-fuels are much more expensive than their fossil counterparts. On the other hand, e-fuels exhibit a lower global warming potential than fossil fuels, which comes at the cost of worsening impacts on human health. In this respect, green H2, and particularly the electricity used in its production, is the largest contributor to the cost and the environmental impact of e-fuels. Thus, it is concluded that the widespread deployment of e-fuels will critically depend on the availability of abundant renewable electricity with low intermittency, low cost and minimal environmental impact.