Powering ahead

E-fuels such as power-to-liquid (PtL) sustainable aviation fuel (e-SAF) are attracting significant attention.
The production technology exists, but barriers remain for large-scale deployment.
Central to overcoming these issues is the choice of production pathway. One of the most promising is the G2L™ process, which integrates Sasol’s Fischer- Tropsch synthesis with Topsoe’s electrified reverse water-gas shift (eREACT™), including light hydrocarbon recycle and product upgrade section. It is so promising, in fact, that it was recently chosen for Europe’s largest e-fuels research and demonstration plant, the Technology Platform Power-to- Liquid Fuels (TPP) of the German Aerospace Centre (DLR).
The efficiency challenge
Producing liquid hydrocarbons from electricity and carbon dioxide is inherently energy intensive. Hydrogen production, via electrolysis, accounts for more than half of the total e-SAF cost, which makes energy efficiency the defining metric for economic viability.
Every megawatt of electricity and kilogram of hydrogen must be translated into the highest possible yield of certified kerosene. G2L™ addresses these issues through the use of eREACT, where electrically heated reactors replace combustion to supply the energy needed for syngas generation.
By eliminating hydrogen combustion, the process improves both hydrogen and electricity efficiency.
On a once-through basis, G2L™ performs comparably to other SAF pathways like the methanol-to-jet process.
However, when recycling integration is introduced, its advantages become clear – G2L™ emerges as the most efficient option, achieving the highest energy and hydrogen efficiency, and enabling the lowest cost of SAF without producing lowvalue heavy products like the methanol-to-jet process.
Efficiencies and savings can be manyfold
One of the defining features of G2L™ is the easy implementation of the recycling of light hydrocarbons such as naphtha back into the process.
In a standard oncethrough system, these coproducts are separated and sold, reducing kerosene yield and complicating offtake agreements for multiple products. With G2L™, light ends are reintegrated alongside fresh CO₂ and hydrogen, converting them into additional jet fuel.
This recycling loop increases kerosene yield to 100% of product output while maintaining more than 95% carbon efficiency.
It also cuts hydrogen and electricity demand, with naphtha recycling alone reducing electricity consumption by around 15% compared to once-through operation.
In a sector where electrolyser costs and power prices dominate economics, these savings are significant RNG as a SAF feedstock when using Topsoe’s syngas technologies RNG (or biomethane) is a purified form of biogas derived from organic waste sources such as agricultural residue, food waste, or wastewater treatment.
Upgraded to meet the quality standards of fossil natural gas, RNG is pipeline-compatible and can be used as a direct substitute for traditional natural gas. This means RNG has great potential to serve as a renewable feedstock for producing SAF due to its renewable origin and compatibility with existing infrastructure.
RNG can either be used locally on-site, primarily as a fuel or for power generation, or injected into natural gas distribution pipelines for broader regional export.
For SAF production, pipeline distribution is a more practical option.
Integration with electrolysis
The G2L™ concept further improves efficiency through integration with high-temperature electrolysis.
Fischer-Tropsch synthesis is highly exothermic, producing steam at temperatures suited to Solid Oxide Electrolyser Cells (SOEC). By feeding this waste heat into electrolysers, the system reduces the external electricity required for hydrogen production.
When SOEC integration is combined with naphtha recycling, electricity demand can fall by up to one third compared with conventional alkaline electrolysis. This integration is a practical method of aligning thermodynamics with cost reduction, turning unavoidable process heat into a valuable resource. Efficiency gains in G2L™ technology strengthen project economics by maximising kerosene yield and reducing hydrogen and electricity consumption.
G2L™ selected for the Technology Platform Powerto- Liquid Fuels (TPP)
The potential of G2L™ as a next-generation e-fuels pathway is underlined by its selection for DLRs Technology Platform Power-to-Liquid Fuels (TPP) in Leuna. Funded with €130 million from the German Federal Ministry of Transport, the TPP will be Europe’s largest PtL demonstration and research facility.
The TPP maps the entire value chain, from RED II-H2 and -CO2 to certified e-SAF, with a capacity of 2,500 t/a PtL. The e-fuels will be comprised mainly of kerosene, using renewable feedstocks such as biogenic CO2 and green hydrogen.
The core aims of the TPP are de-risking the PtL route, supporting industrial scaling, gathering PtL application experience, as well as optimising the PtL process and the fuel (Fuel Design), for example, reducing non-CO2- effects. For G2L™, this deployment represents not just validation in a research environment, but a steppingstone towards widespread commercialisation of PtL production.
The demonstration plant is currently under construction starting operation in Q4, 2027.
Powering forward
This year, Sasol and Topsoe signed a cooperation agreement with DLR and Griesemann (acting as EPC-contractor) to enable the construction, operation and R&D activities of DLR’s e-SAF research and demonstration plant at the Leuna Chemical Complex.
This step forward follows Topsoe and Sasol’s selection in 2024 to deliver G2L™ e-fuels technology for the TPP, integrated with Topsoe’s innovative eREACT™ technology and hydroprocessing technologies as well as with Sasol’s LTFT™ (low-temperature Fischer-Tropsch) technology.
Griesemann Gruppe is working alongside Topsoe and Sasol as the engineering, procurement and construction (EPC) contractor.
For more information: Visit topsoe.com