As the emissions from the combustion of drop-in SAF are comparable to fossil-based jet fuels, except for marginal efficiency gains, the majority of the reductions in GHG emissions originate from the production process. In order to assess the overall climate benefit from using SAF, a Lifecycle Analysis (LCA) is performed to account for all the stages in the lifecycle of aviation fuels. It includes feedstock recovery and transportation, fuel production and transportation, and fuel consumption by aircraft.
The GHG emissions of fuels are provided in terms of gCO2e/MJ, which can be compared to the relevant baseline emissions used for fossil-based jet fuel in order to calculate the overall GHG emissions reduction37.
illustrates the components of typical well-to-wing lifecycle analysis steps for fossil- based jet fuel and SAF.
37Greenhouse gas emissions are expressed as grams of carbon dioxide equivalent (gCO2e) emissions of CH4, N2O and non-biogenic CO2 calculated on the basis of a 100-year global warming potential (GWP), consistent with the Intergovernmental Panel on Climate Change (IPCC). CO2e are calculated per energy unit expressed as megajoule of fuel produced and combusted in an aircraft engine (gCO2e/MJ).
The LCA of a fuel is a complex process and many variables (e.g., origin and type of feedstock, electricity mix, production method) can have a considerable impact on the total GHG emissions.
provides an overview of modelled direct emissions reductions under CORSIA for approved SAF production pathways as of January 2022. Work is ongoing to approve GHG emissions reductions for Power-to-Liquid fuels, but with a fully decarbonised supply chain, emission reductions of up to 100% can be achieved compared to a fossil fuel reference.