The aviation industry is actively seeking solutions to curb emissions, and SAF emerges as a leading option. However, the effectiveness of SAF varies, with many available forms only permitting limited emission reductions due to blending constraints.
The term 'SAF' can be misleading, as it is applied to many synthetic fuels with a carbon intensity below a certain threshold in relation to conventional jet fuel, as defined by various policies and international agreements. This results in a range of fuel blends that sit under the SAF umbrella, which contain varying proportions of synthetic components, most of which are not 100% SAF.
Presently, SAF is typically blended with varying percentages of conventional jet fuel, producing varying qualities of fuel to meet the criteria of international standards, specifically to ensure it contains aromatics in the range of 8-25%. Aromatics are an important component of the fuel as, among other benefits, they enhance lubricity, lower freeze point, and interact with polymer seals in the engines and fuelling systems to help prevent fuel leakage. Traditional jet fuel naturally contains aromatics but many bio-based fuels, such as Hydroprocessed Esters and Fatty Acids (HEFA) and Fischer Tropsch (FT) products, do not. This restricts their use to a maximum blend of 50% with conventional jet fuel, which, in turn, limits emission reductions and falls short of meeting international aviation emission targets for 2030 and 2050.
Moreover, SAF standards do not consider the variety of feedstocks and their associated carbon intensities, which vary across different production processes and supply chains. Enabling diversity of feedstocks will accelerate and support the ramp-up of SAF production.
Despite these challenges, the SAF market presents numerous opportunities. Key areas of focus include increasing the permissible SAF blend in the global fleet, enhancing feedstock flexibility for supply chain security, and expanding production capacity.
Lift off for 100% SAF
Recent developments have resulted in successful demonstrations and test flights using SAF blends. Notably, Virgin Atlantic achieved a milestone with the first transatlantic flight powered entirely by 100% SAF in both engines of a commercial airliner. This was made possible using 'BioForming®' Sugar to Aromatics (S2A) technology, which produces BioForm® Synthesised Aromatic Kerosene (SAK) from sugars.
This synthetic component supplies the necessary aromatics for jet fuel and can be blended with a range of other SAF, accelerating the shift from conventional fuel to sustainable alternatives compatible with existing aviation technology. The various demonstration flights using BioForm SAK have also shown that SAK can be a ‘normaliser’ to ensure different SAF blendstocks can be brought within specification and meet aviation performance criteria.
How BioForm SAK is produced
The BioForming S2A technology generates BioForm SAK, which, when blended with paraffinic blendstocks like HEFA, or Fischer-Tropsch and Alcohol to Jet (AtJ),results in a 100% bio-based jet fuel that is a drop-in 100% replacement for conventional jet fuel. The SAK used in Virgin Atlantic's transatlantic flight was derived from non-edible dextrose from corn, but the process can utilise a wide array of plant sugars, including beet sugar, sugar cane, corn starch, cellulosic sugars from various sources, and other soluble carbohydrates.
BioForming S2A technology is based on traditional petroleum refining processes that are modified to use a sugar feedstock instead of petroleum. The production process involves hydrogenation to stabilise the sugars, a hydrodeoxygenation phase to reduce the oxygen content, and an acid condensation step to produce the aromatic mixture. The aromatic mixture is further separated to produce fractions for gasoline, bio-based chemicals, and SAK. The resulting SAK, with lower polynuclear aromatic content than conventional jet fuel, burns cleaner with reduced particulate emissions, and enhances fuel efficiency. This reduction in particulate matter is crucial for both environmental and air quality considerations.
Creating a SAF economy and beyond
The ability to use 100% SAF, as demonstrated by BioForm SAK, aligns with the goals of reducing greenhouse gas emissions by 2030 and 2050. Government policies promoting increased SAF usage could accelerate production and help the industry meet its decarbonisation targets, without necessitating changes to infrastructure or engine technology.
Additionally, BioForming technology produces a mix of chemical components and has applications beyond aviation. It can be used in various industries to create products like bio-gasoline and bio-BTX (benzene, toluene, and xylenes), essential in manufacturing pharmaceuticals, polymers, textiles, and coatings. This versatility positions the technology as a key player in decarbonising not only aviation, but also road transport and other sectors.
The successful 100% SAF-powered transatlantic flight by Virgin Atlantic marks a significant step forward. BioForm SAK not only opens the door to more sustainable jet fuel, but also contributes to reducing air pollution and offers a versatile, secure, and sustainable solution for the future.
Written by Iain Gilmore, Senior Manager, Catalyst Technologies, Johnson Matthey, and David Kettner, President and General Counsel of Virent.
Read the article online at: https://www.hydrocarbonengineering.com/special-reports/05122023/innovative-bio-based-aromatics-pave-the-way-for-100-sustainable-aviation-fuel/
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