Sustainable Aviation Fuels

Growing concerns over global warming have led to increased awareness among different sectors, including the aviation industry. The aviation industry is at a crossroads, grappling with the pressing need to address its substantial carbon footprint, as it is a significant contributor to carbon emissions (CO₂), and there is increasing pressure globally to address climate change. The aviation sector creates 13.9% of the emissions from transport, making it the second most significant source of GHG emissions in transport after road transport (European Commission). Traditional jet fuels contribute significantly to greenhouse gas emissions, and the urgency of mitigating climate change necessitates a swift transition to cleaner alternatives. This is where SAF comes into play.

SAF offers a lifeline for the aviation sector, providing a viable means to reduce carbon emissions significantly. Derived from sustainable feedstocks, SAF serves as an alternative to conventional fossil aviation fuel, sharing similar chemistry with traditional fossil jet fuel. Today’s most common feedstock used for SAF production is hydro-processed esters and fatty acids (HEFAs, including waste and residue vegetable oils and animal fats). The next generation of sustainable aviation fuels should use residual feedstocks from different industries as the source of raw materials and then utilize thermal conversion processes such as gasification and fast pyrolysis. These technologies are already quite mature and can accept a much larger variety of sustainable feedstocks that are available in large volumes.

SAF feedstocks are less carbon-intensive than fossil feedstocks over their life cycle, there is a certain amount of CO₂ released during the production and refinement of the SAF feedstocks. According to IATA, SAF could contribute approximately 65% of the emissions reduction required by aviation to reach net zero in 2050, confirming the commitment of many of the world’s airlines, airports, air traffic management and the makers of aircraft and engines to reduce CO₂ emissions in support of the Paris Agreement 1.5ºC goal.

Research Work

The work aims to analyse spatial optimization of resource supply, preprocessing, logistics, the conversion system, as well as mid-to-long-term term market demands according to the EU Green Deal and in particular aviation fuel targets. In terms of assessment, a prospective LCA/LCC (Life Cycle Cost) will be carried out. Prospective cradle-to-grave LCA poses methodological and computational challenges, as they should provide an assessment of technologies at a future point in time for both the foreground and background systems considered. LCC metrics will relate to whole chain economics (covering feedstock cost, logistics costs and conversion costs). Decisions address geographical locations, and links to market activities producing the biomass waste feedstock. Thus, multi-objective optimization will be performed considering the prospective LCA/LCC metrics for the scaled-up, integrated technological system.

The compatibility results, conversion processes and feedstock data will be the basis for the scalability analysis, as they will provide information on material and energy flows, equipment types and sizes, feedstock and product specifications, which is the starting point for OPEX, CAPEX, LCC/LCA inventory analysis, optimal plant sizes and locations and estimation of technology (innovative technology to couple solar energy and fast pyrolysis of biomass) barriers and technological learning potential. This work will provide insights into how the EU can reduce geopolitical dependence on biomass imports to produce SAF and enable the processing of mainly domestic carbon-based wastes to ensure the stability and security of fuel supply in Europe.

It should be noted that the present research is directly related to the HORIZON Project Circular Fuels [HORIZON-CL5-2022-D3-02-04 — Technological interfaces between solar fuel technologies and other renewables].