Quantifying the Circularity of a Bioeconomy: A Case Study for Sustainable Aviation Fuel Pathways in the United States

Sabrina Summers; Yuanhui Zhang

doi:10.55845/jos-2025-1243

Authors

Sabrina Summers Department of Agricultural and Biological Engineering, University of Illinois Urbana-Champaign
Yuanhui Zhang Department of Agricultural and Biological Engineering, University of Illinois Urbana-Champaign

DOI:

https://doi.org/10.55845/jos-2025-1243

Keywords:

Circularity Index, Decarbonised Transportation, Hydrothermal Liquefaction, Sustainable Aviation Fuel, Waste Valorisation

Abstract

Decarbonising the aviation sector remains a challenge because long-haul flights rely on liquid fuels. Hydrothermal liquefaction (HTL), a conversion process that utilises elevated temperatures and pressures to produce biocrude from wet biomass, is a potential pathway for sustainable aviation fuel (SAF). Through valorisation of biowaste, SAF pathways may improve circularity by increasing the use of renewable and recovered resources. However, standard lifecycle methods do not quantify resource circularity. Here, a scalable circularity index (0%<CI<100%) was applied to quantify the circularity of jet fuel production in the U.S. aviation industry between fossil fuels, hydroprocessed esters and fatty acids (HEFA, an approved SAF route), and HTL. CI showed that compared to fossil jet, HEFA and HTL increased carbon circularity by 6.80-12.70% and energy circularity by 17.95-31.58%. Uncertainty and sensitivity analysis showed that CIs in both SAF scenarios were highly correlated to feedstock supply and recovery, indicating further opportunities for improvement.

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References

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