Techno-economic assessment of sustainable aviation fuel production from captured CO2

Abstract

In 2023, the aeronautics sector accounted for 2.5% of global energy-related CO2 emissions, having grown more rapidly in recent decades than rail, road, or shipping. While significant progress has been made in the electrification of vehicles and power generation, the aviation industry remains in search of a substitute fuel that can effectively reduce its carbon footprint. Among the technological pathways under consideration, the use of captured CO2 in the Reverse Water-Gas Shift (RWGS) process followed by Fischer–Tropsch (FT) synthesis is an attractive “alternative-to-oil” strategy for the production of Sustainable Aviation Fuel (SAF) This study evaluates the technical and economic performance of a Power-to-Liquids (PtL) plant designed to produce SAF from captured CO2. A central objective of this research was to maximize the kerosene fraction (C8–C16) while ensuring on-specification aromatic content. The system was assessed against key performance indicators, including jet fuel composition standards, energy consumption, carbon emissions, hydrogen and CO2 utilization efficiencies, and overall economic feasibility.

Two primary cases based on the CO2 source were evaluated: 1. Large Point Source (LPS): CO2 captured from an industrial facility (specifically a steel plant) with an annual throughput of 1.88 million tonnes. 2. Direct Air Capture (DAC): CO2 captured directly from the atmosphere at a scale of 0.23 million tonnes per year. The study further distinguished two types of DAC: aqueous calcium looping- and solid sorbent adsorption- based DAC technologies.

While the production scales differ, the DAC case being 8.2 times smaller, the underlying process design remains identical across both scenarios, comprising four main stages: water electrolysis, RWGS, Low-Temperature Fischer–Tropsch Synthesis (LT-FTS), and refining. To maximize SAF production, operating parameters for the two distillation columns in the refining section were judiciously selected, and wax yields were minimized via recycling into the hydrocracker. Consequently, the wax recycle fraction serves as a critical design variable. Furthermore, the refining section utilizes two distillation columns for which two reboiler heating methods were compared: conventional natural gas combustion and electrical heating. Results indicate that SAF production increases alongside the wax recycling fraction, reaching 447,000 and 54,000 tonnes per year for the LPS and DAC cases, respectively, at a 93% wax recycling rate. At a 50% SAF blend, the LPS production satisfies 30% of the annual jet fuel consumption at a major hub like Toronto Pearson, whereas the DAC case satisfies approximately 4%. In both cases, the natural gas-based configuration achieved the lowest Levelized Cost of Fuel (LCOF) at a 100% wax recycle rate. In contrast, the electrically heated configuration attained its minimum LCOF at 93% wax recycle rate in both cases. The LCOF values for the LPS case are consistently lower than those of the DAC case (e.g., 5.21 and 5.58 $ kg-1 SAF for natural gas- and electrically heated reboilers, respectively, in the LPS case, compared to 7.47 and 7.85 $ kg-1 SAF for the corresponding configurations in the DAC case at a 93% wax recycle rate).

This research demonstrated that the environmental viability of producing SAF from captured carbon dioxide is governed primarily by the carbon intensity of the electricity grid, as well as by the carbon capture technology employed and the configuration of the downstream refinery system (i.e., wax recycle fraction and the method used to supply heat to the distillation column reboilers). The process has been engineered to maximize jet fuel production; however, co-products such as wax and heavy residues may act as carbon sinks, potentially enabling net-zero or even net-negative SAF carbon intensities under certain conditions.

Climeworks DAC technology represents the most robust pathway for absolute decarbonization, consistently achieving the lowest carbon intensity (CI). In ultra-low-carbon grids such as British Columbia, it functions as a net-negative carbon sink (via carbon retained in waxes) across nearly the entire operating range, while maintaining a strong carbon-mitigation advantage even under intermediate grids (e.g., Ontario). In contrast, Carbon Engineering DAC operates primarily as a carbon-mitigation pathway rather than a net-negative solution, as approximately one-third of the carbon incorporated into SAF originates from natural gas used in the calciner. Nevertheless, it can still achieve well-to-wake (WtW) carbon intensities significantly lower than those of conventional fossil jet fuel. The LPS pathway consistently outperforms calcium-looping DAC and can achieve net-negative emissions under low-carbon electricity grids at low-to-moderate wax recycling fractions.

Full electrification of reboiler duty is required except in ultra-low-carbon grids. Reliance on natural gas combustion for process heat, particularly at high wax recycle fractions, can cause both Carbon Engineering and LPS pathways to exceed the lifecycle carbon intensity of conventional fossil jet fuel (~3.85 tonne CO2 per tonne SAF), thereby rendering the synthetic fuel environmentally counterproductive.