Renewable fuel options for aviation – A System-Wide comparison of Drop-In and non Drop-In fuel options

Abstract

The air transport sector's contribution to anthropogenic climate forcing is estimated at around 4 %. In this respect, alternative fuels are considered as a key measure to reduce greenhouse gas emissions within the air transport system and thus to reduce the contribution of commercial aviation to anthropogenic climate change. Nevertheless, so far the usage-shares of alternative fuels are below 1 %. Thus, the goal of this paper is to analyse a broad selection of aviation fuel options for their greenhouse gas reduction potential based on a set of nine assessment criteria. The fuel options studied are blended synthetic kerosene and neat synthetic kerosene fuels, three alcohols (methanol, ethanol and butanol) and three gases (methane, ammonia and hydrogen). For these fuels a multi-criteria assessment based on a five-step ordinal scale is performed. The assessment results show that the availability of some biogenic feedstock is not sufficient to replace the present overall energy demand of aviation; while the availability of non-biogenic fuels might increase in the near- to mid-term. In general, alternative kerosene-like fuel options are mainly constrained by lacking production capacities, while alcohols and gases considered are constrained by aircraft modifications or development of new aircraft types. All discussed fuel options have the potential to mitigate greenhouse gas emissions of commercial aviation substantially also from a life cycle perspective. Within the next decade, especially alternative kerosene-like options with (intermediate) products experiencing demand from other sectors, such as FT-SPK or AtJ-SPK, show a high development potential. The same holds for hydrogen provided that a hydrogen fueled aircraft will be brought successfully to the market.