Sustainable Aviation Fuel – An Effective Tool for Complying with the Aviation’s Global Environmental Commitment
Authors: Barbosa Fábio Coelho 
Published: December 2024

<div class="section abstract"><div class="htmlview paragraph">The (commercial) aviation sector (passenger and freight), which is strongly engaged with the world efforts to mitigate the carbon emissions and their inherent climate change effects, has accounted in 2018 for 2.4 % of global carbon dioxide (CO<sub>2</sub>) emissions (pre-pandemic levels). Despite the reductions in air travel demand during the 2020 pandemic, with a reduction of up to 80% in passenger travel during the peak pandemic period, the air travel demand has already recovered to around 80% of the pre-pandemic level, with aviation emissions in 2022 reaching around 800 Mt CO<sub>2</sub>, accounting for 2% of the global energy related CO<sub>2</sub> emissions. Moreover, the demand for air travel is expected to double by 2040, growing at an annual average rate of 3.4%, which means that. despite the efficiency improvement trend (average 2%/year), will almost double the aviation’s greenhouse (GHG) emissions, with a significant increase in its relative GHG share, compared to the other transport modes.</div><div class="htmlview paragraph">Meanwhile the aviation sector is one of the hardest to decarbonize, with few and costly pathways available. Zero emissions technologies, such hydrogen fuel and electric batteries are currently far from commercially ready for aviation use in the short to medium term, due to the technical challenges, such as aircraft onboard liquid hydrogen storage difficulties, as well as battery weight and volume, and are unlikely ever to be able to power large or long-haul flights.</div><div class="htmlview paragraph">In this scenario, the so called sustainable aviation fuel (SAF), a drop-in fuel concept, already available in modest amounts on a commercial scale, are seen as a promising short to medium term alternative to tackle aviation emissions, by using existing aircraft designs and infrastructure. As a drop-in fuel, the SAF enables the replacement for the fossil jet fuel by using the existing fuel delivery and storage infrastructure and existing aircraft engines, with lifespan that still ranges from 20 to 30 years. From a chemical perspective, the SAF is the liquid aviation fuel derived from non fossil carbon resources, such as biomass or organic derived waste feedstocks, as well as synthetic fuels produced from carbon capture and renewable energy sources. They might be currently used in blends with fossil jet fuel, with current blending limits ranging from 5% to 50%, depending on the feedstock and production pathway. It is estimated from the International Air Transport Association (IATA) that to reach the net zero emission commitment, by 2050, around 65% of emission reductions should be reached by replacing conventional jet fuel with SAF.</div><div class="htmlview paragraph">Despite its important role in the aviation decarbonization, the SAF share currently makes up only 0.1% of aviation fuel demand, which requires a huge increase in the production capacity, which might face challenges, such as feedstock availability, fuel sustainability and cost competitiveness.</div><div class="htmlview paragraph">This work presents a review of the SAF technology, with a focus on the production pathways and their environmental footprint, their use on current aircraft engines and the associated required blends, as well as the challenges associated with SAF production increase and cost reductions, still required to make it a realistic aviation decarbonization tool.</div></div>