Carbon Neutral Fuels unveils ‘FlexSAF’
Carbon Neutral Fuels announced Oct. 13 that it is unveiling “FlexSAF,” a flexible plant design that enables the production of both electro sustainable aviation fuel (eSAF) and advanced biobased SAF at a single facility.
Debuting at CNF’s flagship Project Starling site in Workington, West Cumbria, U.K., CNF said the FlexSAF design’s higher output contributes to solving the SAF supply gap, where industry professionals are concerned that statutory U.K. and EU SAF mandates are rising faster than dedicated production capacity can be built.
By integrating dual feedstock pathways—eSAF from biogenic CO2, water and renewable electricity, and advanced bioSAF from biomethane—FlexSAF gives Project Starling a more diverse feedstock base.
Both pathways feed into a single, shared Fischer-Tropsch synthesis and upgrading line, increasing SAF target output to approximately 42,000 metric tons per year.
This shared infrastructure is expected to significantly lower the production cost per ton of fuel while offering flexibility within plant parameters to adjust the production mix in response to feedstock availability and market demand.
Process optimization work has expanded target SAF production by 70 percent, taking Project Starling from 25,000 tons to approximately 42,000 tons of SAF annually.
By recycling the byproducts of naphtha and tail gas back into the syngas stream, CNF said virtually all output is converted directly into aviation-grade jet fuel.
This commercial-scale hybrid design is expected to be a U.K. first, the company said.
“We’re so glad we can finally talk about FlexSAF,” said Alasdair Lumsden, CNF’s co-founder and director. “Making eSAF and advanced bioSAF in one plant allows us to shift the balance as the market develops—within the limits of the equipment—a kind of agility that is rare in these large production facilities, and which matches our ethos of creating the right design for the location. Aviation in the U.K. needs every scalable route to low-carbon fuel it can get. FlexSAF gives us two, and the scaling means a lower cost for every ton of homegrown SAF.”
Sophie Zienkiewicz, also a co-founder and director of CNF, added, “The U.K. currently imports more than 70 percent of its aviation fuel. Deploying FlexSAF at Workington will transform an underused 40-acre brownfield site into a sovereign energy asset, creating more than 500 construction jobs and over 150 skilled operational roles while helping secure the U.K.’s clean-fuel supply. We’re excited to unveil this new design before meeting with locals on Oct. 15 for our public drop-in session. Given West Cumbria’s rich history of energy innovation, we’re looking forward to discussing the design and answering questions from the community.”
Following the signing of a planning performance agreement with Cumberland Council in June, CNF was scheduled to host a public drop-in session for the local community Oct. 15.
A full planning application will follow in spring 2028, targeting first fuel production by late 2031.
“With FlexSAF, both routes feed into the same fuel-making and upgrading equipment, giving us two pathways without building two separate plants,” said Stephanie Ng, project director at CNF. “It’s the type of project that’s really satisfying to work on as an engineer at heart, because it’s an elegant engineering solution to a market issue.”
