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February 5, 2024

e-SAF offers much promise within Sustainable Aviation Fuels

This article first appeared in Sustainable Aviation Futures and is reproduced with their kind permission.

The aviation industry is embarking on a strong growth journey following the Covid-19 years. The International Air Transport Association (IATA) noted that by March 2023, industry-wide revenue passenger-kilometers (RPKs) had surged to 88% of pre-pandemic levels. The long-term outlook is also soundly positive with the IATA predicting demand for air travel will double by 2040, with origin-destination passengers projected to increase from approximately 4 billion in 2019 to over 8 billion in 2040. This growth outlook is obviously positive for the industry, but it makes cutting emissions even harder. 

Improved aircraft design, enhanced technology, and optimized ATM systems will yield benefits in terms of decarbonization. But the true impact lies within the nature of the fuel itself, with SAF projected to contribute more than 60% of aviation’s decarbonization. However, in 2022, global SAF production increased three-fold from 2021 but remained at less than 0.1% of what is required for 2050 net zero targets. Importantly, airlines used every single liter of SAF produced in 2022, highlighting the existing supply-side challenge.

Co-processing, HEFA and 2nd gen feedstocks are short-term winners
Presently, HEFA is used for almost all SAF, but feedstocks of waste oils and fats (second generation feedstocks) are resource-constrained and are already largely consumed by the road transport sector.
Initially co-processing, which allows refineries to convert renewable feedstocks into drop-in, biojet fuel at economically competitive prices, can swiftly boost the availability of SAF. But long-term other approaches will be necessary. In the short to medium term, we will see more and more existing refineries upgrading, diversifying, or reconstructing their operations to produce SAF from FT-SPK or HEFA pathways. 

By the end of 2022, eight refineries in the United States had completed conversions to produce Renewable Diesel (RD) or Sustainable Aviation Fuel (SAF), or a combination. A year later, an additional six sustainable fuels plants joined their ranks in the US. In this diversifying landscape, we see gasification, FT (Fischer Tropsch) and hydrocracking further ramping up of SAF production. 

eFuels go beyond blue-sky thinking
eFuels and emerging pathways will increasingly play a crucial role in diversification to tackle feedstock obstacles. A wider array of feedstocks will take on greater significance, including municipal solid waste, alternative waste sources, and plastics. These resources will undergo conversion into SAF through methods like, pyrolysis, and gasification, Fischer-Tropsch.

eFuel, specifically eSAF in aviation, holds massive potential. eSAF is produced through the combination of green hydrogen (renewable electricity is used to separate hydrogen from water via electrolysis) with CO2 captured from the atmosphere or biogenic sources. eSAF has substantial supply potential since the future availability of renewable electricity and CO2 may not be not constrained in the same manner as with other SAF feedstocks. 

eSAF technology is already here
Topsoe’s G2L™ eFuels solution enables the production of sustainable synthetic fuels, including eSAF, from green hydrogen and biogenic CO2, with much of the required infrastructure, certification and legislation is already in place.

The commercially proven G2L™ solution has served energy companies for years, enabling them to transform natural gas and methane rich gas into a range of high-quality fuels. The G2L™ eFuels solution combines these well-known processes with breakthrough technologies for producing sustainable liquid fuels: from renewable energy via green hydrogen, and from CO2 via carbon capture.

SynCOR™ technology has been the reliable and optimal choice for Gas-to-Liquids plants using natural gas feedstock for many years. This technology has been adapted to convert CO2 and hydrogen through our two-step RWGS (Reverse Water Gas Shift) process; a fully commercialized process that gives high conversion rates. With the novel eREACT™ Fuels technology, the process is further electrified, meaning syngas can be produced from renewable energy, water and CO2 in a very compact reactor.

The Sasol Low Temperature Fischer Tropsch™ technology relies on a catalytic process to convert carbon monoxide and hydrogen to long-chain, largely paraffinic molecules. These are ideally suited for producing synthetic kerosene for jet fuel and diesel fuels. The technology (including the Topsoe PWU process to convert FT products to SAF) and catalyst are in commercial operation in various plants across the globe.

A facility dedicated to producing SOEC (solid oxide electrolysis cell) electrolyzers is also currently being constructed by Topsoe in Herning, Denmark. Facilities like this represent an important step in scaling up and streamlining production, which can lead to lower costs and higher efficiency in manufacturing electrolyzers. Access to this type of technology may play a key role in the future of eSAF, since it can be used in Power-to-Liquid processes, opening up for eMethanol and, by extension, the Methanol-to-Jet pathway. Topsoe’s ModuLite™ eMeOH plants enable the rapid deployment of methanol-synthesis solution built on decades of experience. Modular, renewables-optimized and in capacities up to 600 MTPD, Topsoe's eMethanol and ModuLite technologies are ready to support the Methanol-to-Jet takeoff.

Getting prepared for eSAF takeoff
While holding significant potential, the production of eSAF is still costlier compared to HEFA (attributed to the high cost of green H2), demands a significant amount of energy, and hinges on the expansion of both clean electricity generation and CO2 sourcing, such as Direct Air Capture (DAC) or biogenic CO2. The commitment from over 100 countries to triple renewable energy capacity by 2030 at COP28 summit in Dubai shows we are heading in the right direction.

While important to acknowledge and appreciate the leadership shown by the US and EU in providing an increasingly clear regulatory SAF framework overall, more ambitious actions are necessary to ensure the swift and effective implementation of these policies, especially around eSAF. 

Financial incentives are crucial for de-risking private investments and creating a robust market. In the US, we hope for the extension of SAF tax credits beyond 2027. Additionally, the EU should consider increasing the budget of the European Hydrogen bank to support the production of renewable hydrogen for eSAF and redirect revenues from the Emissions Trading System (ETS) towards price support mechanisms that bridge the gap between SAFs and fossil fuels. Meaningful, financially sound offtake agreements from airlines will also enable investment transparency.

There needs to be an overall focus on the development and adoption of third-generation feedstocks and eFuel production. This can be achieved through increased investment in research and development as well as prioritization of aviation’s need for renewable energy. Additionally, support for infrastructure and logistics can also smooth eSAF’s commercialization. 

Then we can finally expect an eSAF takeoff.  


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