Ph.D. defense entitled: Assessing the environmental performance of future sustainable aviation systems: methodological development and evaluation by life cycle assessment
- Catherine Azzaro-Pantel, Professor, Toulouse INP-ENSIACET - President of the jury
- Benoît Gabrielle, Professor, Agro Paris Tech, Rapporteur
- Robert Malina, Professor, Hasselt University, Rapporteur
- Sandra Beauchet, IFPEN Research Engineer, Examiner
- Florian Simatos, Professor, ISAE Supaero, Examiner
- Lorie Hamelin, Researcher, INSA Toulouse - Thesis director
- Ligia Tiruta-Barna, Professor, INSA Toulouse - Thesis co-director
This PhD work proposes and applies a methodology to compare and anticipate, by life cycle assessment (LCA), the environmental consequences of investments into four key emerging alternatives aviation systems to fossil kerosene. This includes biofuels (from waste cooking oil (WCO) or forestry residues), electrofuels (from atmospheric/industrial CO2, combined with renewable H2), electric battery, and H2 systems (either combustion or within fuel cells). This works focus on commercial aviation (passengers and cargo), this representing 88% of the CO2 emissions from global aviation.
Four pathways for biofuels (hydroprocessed esters and fatty acids (HEFA) with WCO, biomass gasification followed by either Fischer-Tropsch (FT) or syngas fermentation and alcohol upgrading (Ethanol-to-Jet), and sugar fermentation and alcohol upgrading (as Isobutanol-to-Jet), two for electrofuels (carbon capture technologies based on liquid or solid sorbent), four for Li-based batteries, and two for water-splitting H2 production have been studied.
Full electric systems are considered only for the domestic segments (19 passengers plane). Hybridization with fossil kerosene is considered for the international segments. The comparisons are made based on the following functional unit: “Ensuring the annual global supply in 2035 of 6 trillion revenue passenger kilometres (RPK) of domestic flight and 9 trillion RPK of international flight”, itself based upon forecasts of International ICAO
(International Civil Aviation Organization )
The comparative framework built within this PhD work covers essential issues typically disregarded in previous analyses, including the fact that: i) under current framework conditions, liquid fuel alternatives require blending with fossil kerosene; ii) residual biomasses, when mobilized for aviation, are diverted from another use (counterfactual use); iii) fuels may affect the type and number of aircraft needed to supply the service described by the functional unit, among others because of an induced mass penalty; iv) some of the systems imply additional infrastructure, including for the end-of-life, and v) a fair comparison requires considering non-CO2 climate forcers such as NOx, induced cloudiness, water vapor, black carbon, sulfate.
Two time scopes are considered (near- and long-term). The main differences are: (i) the long-term assumes that blending with fossil kerosene will no longer be required, and (ii) natural gas is used as a heat source in the nearterm while heat is fully electrified in the long term.
In total, 16 impacts were quantified, and six were studied more finely, including climate change, photochemical ozone formation, particulate matter, freshwater eutrophication, marine eutrophication, and water use. Climate results indicate, in both the near- and long-term, that all scenarios perform better than fossil kerosene, except for HEFA in the near-term. This is due to the counterfactual use of WCO for heat, then supplied by natural
gas. Biofuels and electrofuels are heavily penalized by the blending requirements with fossil kerosene in the nearterm; this also applies to hybrid electric battery systems (international segments, both time horizons). All H2 systems, as well as the biofuels (besides the HEFA) and the full electric systems, achieve net zero (or negative) climate impact. For the two formers, this is explained by the important amount of heat recovered from both the
gasification process and the H2 production, translating into avoided natural gas. For this reason, results are quite different in the long-term, where systems whose performance is less dependent upon recovered heat (biofuels, full electric, H2) are those closer to a zero climate impact performance. Other impacts are mostly driven by electricity.
et les systèmes entièrement électriques, ont un impact net nul (ou négatif) sur le climat. Cela s’explique par l’importante quantité de chaleur récupérée à la fois dans le processus de gazéification et dans la production d’hydrogène, ce qui se traduit par une économie de gaz naturel. C’est pourquoi les résultats sont très différents à long terme, les systèmes dont la performance dépend moins de la chaleur récupérée (biocarburants, tout électrique, et H2) étant plus proches d’une performance à impact climatique nul. Les autres impacts sont principalement dus à l’électricité.
Keywords: Batteries (Electric); Biofuels; Electrofuels; Energy Transition; Hydrogen (H2); Life Cycle Assessment (LCA); Sustainable Aviation Fuels (SAF); Sustainable Aviation