Unravelling the potential of sustainable aviation fuels to decarbonise the aviation sector

Abstract

The aviation industry is responsible for approximately 2% of the total anthropogenic greenhouse gas emissions. With an expected four to six-fold growth by 2050, increased attention has been paid to reduce its carbon footprint. In this study, we analyse the requirements to promote Sustainable Aviation Fuels (SAFs) from solar energy to reduce the emissions of the sector. Using a discrete spatio-temporal mathematical description of the region of Spain, we present the key elements required to produce jet fuel via Fischer–Tropsch (FT) and Methanol to fuels (MtF). We have found that solar PV, electricity storage, and alkaline water electrolysis are the key drivers for the performance of solar SAFs while the optimal location of the facilities is driven by the availability of solar radiation, underground H₂ storage, and high jet fuel demand. We show that the constant supply of H₂ requires an over sizing of technologies, which in turn decreases the utilisation of solar panels and electrolysers. While higher usage rates could be attained by a constant supply of electricity (e.g., via the electricity grid), the use of renewable sources is essential to guarantee a reduction in CO₂ emissions compared to fossil-based jet fuel. We found that production costs in 2020 per kg_fuel in Spain varied from 3.90 € (MtF) to 4.95 € (FT) using solar radiation as a sole source of energy and a point source of CO₂, cutting CO₂ life cycle emissions by ∼25% compared to their fossil-based counterpart (2.5–2.7 kg_CO2eq per kg_fuel). Potential technological improvements could reduce jet fuel production costs to 2.5–3.3 € per kg_fuel for CO₂ point sources while emissions could reach ∼1.0 kg_CO2eq per kg_fuel. Ultimately, the impact of these routes in the cost of a flight ticket would result in a minimum increase of 100–150% at present and 40–80% by 2050, accounting for current projections on technologies and carbon prices. This shows that future minimum carbon taxes of 500 € per tCO₂ would be required for SAFs to become competitive.