Decarbonisation Technology - May 2024 Issue

Oshore wind

Complementary renewables (solar and wind)

Green power connection (24/7)

Fossil jet fuel (reference)

Renewable power (solar and wind hybrid) Water electrolysis Hydrogen storage Synthesis plant (RWGS + Fischer–Tropsch + Upgrading) CO from a point source

Challenges in bio-SAF and eSAF production Shell recently conducted a case study for a PTL production scenario in the Middle East in 2030 (see Figure 2 ). In this scenario, the investment in renewables, electrolysis, and storage (stable supply of renewable hydrogen) would be four times higher than that in the synthesis plant where the hydrogen and CO₂ are converted into eSAF. Over time, the costs associated with renewable hydrogen production are expected to decrease owing to technology improvements and intermittency solutions, including flexible operation of the synthesis plant. The study also showed that combined bio-SAF and eSAF production is a cost-effective solution, with anticipated costs 15% to 30% lower than a standalone eSAF PTL project with a point source of CO₂. In the case of DAC, this delta in costs would only further increase. Another Shell analysis shows how location affects the cost of PTL (see Figure 3 ). Advantaged locations include those with hydropower, benefitting from a 24/7 stable renewable power supply, followed by a combination of solar and wind power in locations close to the equator. Nuclear power can also play a role (it is accepted for meeting mandates under ReFuelEU Aviation, though not for RED targets for RFNBO). Figure 3 Relative PTL production costs in 2030, $/t(fuel)

biomass presents a challenge for hydrocarbon fuel production. Adding renewable hydrogen to a BTL process facilitates the full utilisation of biogenic carbon in the biomass instead of emitting (‘losing’) some of the carbon in the form of CO₂. In this case, the production becomes partially BTL and partially PTL. • Scale efficiency and cost: Joint production of bio-SAF and eSAF requires smaller-scale electrolysers when compared to a pure PTL process. Given the present elevated cost of electrolysers, this method has a competitive edge, especially for early projects, with the expectation that electrolyser costs will decline in the future. • Simplified process without RWGS: Although RWGS has a high technology readiness level, at the time of writing (February 2024) it is not fully de-risked for large-scale commercial applications. In bio-SAF and eSAF co- production with a limited PTL component, RWGS can be eliminated. • Scale-related benefits: An integrated strategy combining bio-SAF and eSAF uses larger Fischer–Tropsch and hydroprocessing units, resulting in economy of scale. Figure 2 Breakdown projection of the levelised production cost of synthetic aviation fuel using PTL technology in the Middle East