Title : Life-Cycle GHG of SAF in real flights: Empirical WTW accounting and reconciliation with TIM, DEFRA, and base empreinte
Abstract:
Sustainable Aviation Fuels (SAF) are central to aviation decarbonisation, but their climate benefits are rarely evaluated on real flights using consistent well-to-wake (WTW) methods. This presentation quantifies WTW greenhouse-gas (GHG) intensities for 5–10 commercial flights using certified SAF blends based on three archetypes: HEFA, Fischer–Tropsch (optionally with BECCS) and Power-to-Liquids (RFNBO). We combine primary flight telemetry (origin–destination, block time, fuel burn, aircraft type, seat map) with ISO 14067/14083-aligned life-cycle inventories to compute flight-specific WTW CO?e in gCO?e/MJ, gCO?e/pkm and tCO?e/flight.
The empirical WTW results are benchmarked against three widely used reporting approaches in corporate and travel emissions accounting: Google’s Travel Impact Model (TIM), the latest DEFRA factor sets and ADEME/Base Empreinte. All three methods are run on the same flight sample, under their native assumptions, to quantify method-driven dispersion and to isolate sources of divergence such as tank-to-wake (TTW) versus WTW scope, treatment of SAF blends and biogenic CO?, non-CO? handling and class/cargo allocation. Agreement metrics (MAE, MAPE, RMSE), Bland–Altman plots and stepwise toggling (TTW → WTW → non-CO? → class allocation) are used to attribute gaps for each method relative to the empirical WTW benchmark.
Building on this comparison, we propose a minimal, auditable accounting protocol that makes SAF use visible in corporate Scope 3 reporting without requiring major changes to existing tools. Key elements include explicit TTW/WTW separation, a declared non-CO? option with radiative forcing index sensitivities, energy-based blend math, transparent biogenic CO? treatment and version-locked emission factors. Preliminary results indicate that method differences, rather than operational variance, dominate long-haul CO?e dispersion when SAF is present. Applying the protocol substantially reduces inter-method spread while remaining compatible with CSRD/ESRS, ISO 14083 and CORSIA. The study provides practical guidance for airlines, corporates and intermediaries seeking to align aviation GHG accounting with real-world SAF deployment.
