Sustainable aviation fuel production using in-situ hydrogen supply via aqueous phase reforming: A techno-economic and life-cycle greenhouse gas emissions assessment

Abstract

Sustainable aviation fuel (SAF) production is one of the strategies to guarantee an environmental-friendly development of the aviation sector. This work evaluates the technical, economic and environmental feasibility of obtaining SAFs by hydrogenation of vegetable oils thanks to in-situ hydrogen production via aqueous phase reforming (APR) of glycerol by-product. The novel implementation of APR would avoid the environmental burden of conventional fossil-derived hydrogen production, as well as intermittency and storage issues related to the use of RES-based (renewable energy sources) electrolysers. The conceptual design of a conventional and advanced (APR-aided) biorefinery was performed, considering a standard plant capacity equal to 180 ktonne/y of palm oil. For the advanced scenario, the feed underwent hydrolysis into glycerol and fatty acids; hence, the former was subjected to APR to provide hydrogen, which was further used in the hydrotreatment reactor where the fatty acids were deoxygenated. The techno-economic results showed that APR implementation led to a slight increase of the fixed capital investment by 6.6% compared to the conventional one, while direct manufacturing costs decreased by 22%. In order to get a 10% internal rate of return, the minimum fuel selling price was found equal to 1.84 $/kg, which is 17% lower than the one derived from conventional configurations (2.20 $/kg). The life-cycle GHG emission assessment showed that the carbon footprint of the advanced scenario was equal to ca. 12 g CO2/MJSAF, i.e., 54% lower than the conventional one (considering an energy-based allocation). The sensitivity analysis pointed out that the cost of the feedstock, SAF yield and the chosen plant size are keys parameters for the marketability of this biorefinery, while the energy price has a negligible impact; moreover, the source of hydrogen has significant consequences on the environmental footprint of the plant. Finally, possible uncertainties for both scenarios were undertaken via Monte Carlo simulations.