As the aviation industry seeks to reduce its carbon footprint, Sustainable Aviation Fuel (SAF) has become a crucial part of the conversation as the most viable option to decarbonise flights for the next decade and beyond. SAF can significantly cut emissions compared to traditional jet fuel, but there are several ways to produce it. Each production pathway offers its own set of advantages and challenges. Here’s a look at four of the main pathways and what they might mean for the future of aviation.

  1. HEFA (Hydroprocessed Esters and Fatty Acids)

HEFA is the most established method for producing SAF today. It uses feedstocks like waste oils, animal fats, and vegetable oils to produce a fuel that can be used in existing aircraft engines without modification.

Why It’s Important: HEFA is popular because it can be scaled relatively quickly due to the maturity of the production technology and the ability to re-purpose existing refinery infrastructure. This means that HEFA facilities can be developed and constructed with significantly less CAPEX compared to advanced 2nd generation routes to SAF.

The cost of production is cheaper than other pathways, such as Gasification + Fischer Tropsch or AtJ. This makes it a strong candidate for meeting immediate demand.

Challenges: The main challenge with HEFA is the limited availability of feedstocks. As more industries compete for these resources, the cost could rise, and supply may become a bottleneck. There are also HEFA caps being implemented on the policy and regulatory side which will limit the scalability.

  1. Gasification + Fischer-Tropsch

This pathway involves turning solid materials like biomass or municipal waste into gas, which is then converted into liquid wax through the Fischer-Tropsch process. Waxes are then upgraded in conventional refinery hydroprocessing steps to produce SAF and by-product naphtha. SAF produced in this way is called Fischer Tropsch synthetic paraffinic kerosene (FT-SPK). It’s a more complex method than HEFA but has the potential to produce large amounts of SAF.

Why It’s Important: Gasification + Fischer-Tropsch can use a wide range of feedstocks, including materials that would otherwise go to waste. This makes it a promising option for large-scale SAF production, especially in areas with abundant biomass or waste resources.

Challenges: The technology is complex and expensive to scale. Building and operating these plants requires significant investment which can be challenging in a nascent market. Policy and regulatory support is essential to enable this pathway to scale at pace.

  1. Alcohol-to-Jet

Alcohol-to-Jet (AtJ) converts alcohols, like ethanol, into jet fuel. This method can be particularly appealing in regions with established alcohol production industries.

Why It’s Important: AtJ can leverage existing ethanol production infrastructure, which means it could be easier and cheaper to implement in some geographies. It also offers flexibility in terms of the types of feedstocks that can be used.

Challenges: The technology is still in the early stages, and there are technical hurdles to overcome, such as improving the efficiency of the conversion process to make it commercially viable.

  1. Power-to-Liquid (eSAF)

Power-to-Liquid, also known as eSAF, is a cutting-edge approach that involves creating fuel from renewable electricity, hydrogen, and captured CO2. This pathway is seen as a long-term solution for truly sustainable fuel.

Why It’s Important: eSAF has the potential to produce jet fuel with a very low carbon footprint. Since it doesn’t rely on biological feedstocks, it avoids many of the sustainability issues associated with other methods.

Challenges: eSAF is still in its infancy. The technology is expensive, and the infrastructure needed to produce it on a large scale isn’t fully developed yet. It will take several years before eSAF can be produced in significant quantities.

The future of scaling SAF lies in utilising a mix of these pathways, especially in the early stages of the energy transition. HEFA is currently leading the way, but as technology and infrastructure develop, other methods like Gasification + Fischer-Tropsch, Alcohol-to-Jet, and Power-to-Liquid will play increasingly important roles. Each pathway has its own strengths and challenges, and the best approach may vary depending on regional resources and technological advancements. As the industry continues to innovate and countries seek to reach their Net Zero targets, SAF will become a critical component in reducing aviation’s environmental impact.