How big is big enough? Cost-optimal design for centralized and decentralized e-SAF production

Abstract

Converting biogenic CO₂ into synthetic sustainable aviation fuel (e-SAF) requires significant amounts of renewable energy, and alignment between system elements and sizes. However, the optimal scale and configuration of CO₂ electrolysis remains unresolved. This study examines the economics of RFNBO-compliant e-SAF production from CO₂ electrolysis via Fischer–Tropsch synthesis in centralized and decentralized configurations in the Netherlands. A two-stage optimization framework sized the renewable generation, storage, and use of grid electricity for electrolysis plants (9–900 MW). The model projects scenarios from 2025 to 2050, including expected cost and efficiency improvements. The lowest near-term (2025) levelized cost of e-SAF (around 5230 EUR₂₀₁₉/tonne) is achieved for a centralized 90 MW electrolysis plant powered by onshore wind and photovoltaics. A 23 MW decentralized system yields comparable costs. While conversion investment costs are higher at smaller scales, they are counterbalanced by avoided grid fees, higher allowed grid mix electricity consumption, and lower CO₂ supply cost. By 2050, decentral e-SAF production costs are projected at 2750 EUR₂₀₁₉/tonne (a 35–70% premium over current SAF prices). These systems provide a near-term route for demonstration projects by co-locating renewable energy, e-SAF production, and regional airports. However, two fundamental caveats remain. First, the cost of CO₂ electrolysis–based fuels is incompatible with bulk fuel margins. Second, the limited production volumes from a decentralized configuration are misaligned with the high demand of the aviation sector. Therefore, CO₂ electrolysis appears best deployed in a high-value niche product or where high-quality renewable resources geographically overlap with distributed biogenic CO₂ streams.