The aviation sector is one of the largest sources of greenhouse gas (GHG) emissions, accounting for 2% of global CO2 emissions in 2022, with emissions potentially tripling by 2050 without intervention. In light of these events, the most promising avenue to cut emissions is through the use of Sustainable Aviation Fuels (SAF), although their impact remains limited due to numerous barriers that do not allow SAF blend ratios above 50%. Therefore, the main objective of this research is to systematically investigate the current barriers to blending limits of SAF specified under existing regulations and develop a comprehensive strategy which mobilises stakeholders. While existing literature addresses future uptake of SAF blends, identified barriers and coupled strategies are unclear, underdeveloped and dispersed, with regulatory mechanisms at times inefficacious. Furthermore, although collaboration among stakeholders is encouraged, it is unclear what roles individual stakeholders should take on to approach certain problems.

The research was conducted using a qualitative approach. The sample was composed of 14 specialists ranging from different key stakeholder groups. These key stakeholder groups were largely located in the higher rungs of the participation continuum, a model used in the stakeholder analysis which placed stakeholders along the continuum based on their level of participation in the SAF ecosystem. Semi-structured interviews then collected data, which were translated into codes. Using the Technological Innovation System (TIS) and its seven building blocks as a framework, all identified codes were grouped under one of the TIS building blocks. Based on this, three analyses were performed in parallel: barriers of SAF blending were identified, SAF production methods were compared against one another based on method-specific barriers, and strategic measures were formulated to overcome identified barriers alongside the actors who are responsible for enacting them. This, however, deviated from the TIS framework in the sense that it formulated a strategy for an entire industry and how stakeholders can collaborate as opposed to the formulation of a strategy for a single firm.

SAF blending above 50% is found to hold little to no priority among the SAF industry, which rather prioritizes upscaling of available capacity. This is because there is currently too little blend component available to achieve high blend percentages, regulatory limits do not instil an urgency to increase blends due to being small in number, and SAF supply methodologies are configured such that all SAF is blended to the bare minimum mandated. Only when such barriers are removed, and more blend component becomes available in the future, an increase in blend ratios and removal of the blend wall will be necessitated to achieve a higher sustainability impact of SAF in flight.

For SAF itself, it is found that the majority of TIS building blocks remain incompatible or partly incompatible. Product performance and quality are sufficient to some degree given that SAF can already be used in existing aircraft, but remain limited to blends of 50%. Product price is largely incompatible, the most cost-efficient SAF still being at least twice as expensive as conventional fuel due to energy-intensive processes and lack of technological maturity. The production system is similarly incompatible, projected to produce insufficient quantities of bio-SAF and e-SAF by 2030 due to long construction times and limited financial resources. Institutions and regulations are partly incompatible as they are widely in place but remain scattered and unclear. Network formation and coordination also remain partly incompatible, with limited participation and coordination concerning sustainability transitions. Uptake among customers remains limited due to their lack of knowledge and trust in SAF combined with the limited means by airlines to communicate. Only complementary infrastructure and services are fully compatible.

In terms of comparison between production methods, hydro-processed esters and fatty acids (HEFA) performs the best concerning product price and production system because it is a more mature technology. On the other hand, alcohol-to-jet (ATJ), catalytic hydrothermolysis jet (CHJ), and Fischer-Tropsch (FT) are still underdeveloped and more expensive, yet fall under the same mandated share of bio-SAF as HEFA, which causes them to be minimally stimulated. However, given HEFA’s limited impact due to its feedstock constraints, FT, ATJ, and CHJ technologies show future promise because they hold more potential with respect to unlocking the blend limit and have a larger pool of feedstock available. The same holds for synthetic SAF (e-SAF), although its energy-intensive processes remain a large bottleneck for future upscaling.

Paired with each identified key challenge comes an array of measures and actors that enables the industry to overcome these challenges. Mandates and regulations alongside incentives and subsidies most commonly contribute to bridging challenges concerning price, production system, and regulations. Meanwhile, product quality, performance, and infrastructure require further developments in technology and designated infrastructure. For network formation, stakeholder coordination, and customers, emphasis is more often placed on knowledge building and sharing, networking, and raising awareness. Depending on the context of the challenges and coupled measures, different levels of participation are required among stakeholders.

From these findings, the research reveals a comprehensive overview of barriers to large-scale SAF adoption. The application of the TIS framework in a multi-actor system broadens the perspective on barriers and strategies beyond the level of individual firms, illustrating that the strategies to help overcome the barriers are not enacted by a single stakeholder. Instead, to achieve the successful introduction of SAF, dynamic collaboration and coordination within the industry are required, with each stakeholder fulfilling different roles when faced with different challenges.
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