Assessment of alternative aviation fuels development (ALTERNATE )

Greenhouse gas (GHG) emissions from international aviation have been growing significantly in the last decades due to increases in passenger air transport. The use of sustainable aviation fuels (SAF) is considered the most promising short-term option to reduce GHG emissions and mitigate climate change in line with the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). There is still significant uncertainty about the actual environmental impacts and economic viability of SAFs, as well as on the market-based mechanisms and policies needed to promote SAF deployment. ALTERNATE proposes to combine life cycle assessment (LCA), economic modelling, combustion chamber and complete engine tests – among other techniques – to examine the potential climate change effects and technical, economic and  environmental consequences of SAFs use on a commercial scale.

The main objectives of ALTERNATE include:

1. To improve physical and climate models to represent increased SAF use and technical and sustainability implications.
2. To develop a reliable LCA approach for assessing the GHG emission intensity of several bio-based SAF pathways, consistent with CORSIA.
3. To reduce the fuel production costs and hurdles in drop-in jet fuel certification.
4. To provide protocols and guidance for increasing market shares of SAF use in the aviation sector.

To fulfil these objectives, ALTERNATE will carry out the following tasks:

• To identify and evaluate the GHG performance of advanced bio-based feedstocks and their corresponding conversion pathways, by means of both attributional and consequential LCA to also include emissions from Indirect Land-Use change (ILUC).
• To test and model the performance of SAFs in combustors and engines, starting with the preparation of a fuel property database and elaborating models and tools for drop-in fuel certification.
• To study the combustion of various SAFs at different scales ranging from laboratory to complete engine tests. This will allow understanding the relationship between the fuel composition and its combustion behaviour.
• To evaluate different options available for the introduction of SAFs in the normal operation of airlines.
• To propose and evaluate mitigation strategies based on the use of several SAF pathways and different market-based mechanisms.

IIASA is leading WP2, while also participating in WP3 and WP6 in collaboration with project partners. In WP2, IIASA is contributing to the assessment of the market-mediated impacts of increasing production of feedstocks for SAFs at the global level, based on the GLOBIOM model – developed and maintained at IBF. The Deliverables submitted to date include the selection of potential feedstocks of interest for both EU and Chinese partners (D2.1); the collection of life cycle inventory data for attributional LCA (D2.2); and the estimation of ILUC and associated GHG emission factors of selected ALTERNATE feedstocks (D2.3), with a comprehensive uncertainty analysis (D2.4). In WP3, IIASA has been contributing to the development of the LCA methodology, under the lead of University Hasselt (Belgium). In WP6, the GLOBIOM model has been applied for the assessment of land use dynamics and global GHG emissions under several scenarios of SAF deployment considering different interventions.

Overall, ALTERNATE is expected to identify the most sustainable feedstocks and incentives to contribute to CORSIA and the carbon-neutral growth of the international aviation sector.