Waste valorization offers a sustainable pathway to reduce emissions and provides a low-cost feedstock for SAF production. Rather than relying on business as usual (BAU) waste management landfilling or incineration, these wet organic wastes, such as food waste, sludge, and manure, can be processed via arrested anaerobic digestion (aAD) to produce volatile fatty acids (VFAs), which serve as promising intermediates for SAF production [2]. However, the commercialization of VFA-SAF pathways is constrained by low VFA productivity, costly downstream purification, and inefficient product recovery [4].
This project demonstrates an integrated bioprocessing strategy using anaerobic membrane bioreactors (AnMBRs), enhanced with bioaugmentation, hydraulic mixing, and intermittent biogas sparging. AnMBR is a promising technology for continuous VFA recovery from the aAD process, enabling low-turbidity extraction, reducing product accumulation, and preventing microbial washout for stable, efficient operation. Bioaugmentation with selected monocultures significantly improves VFA yields, while hydraulic mixing promotes uniform reactor conditions, reduces foam and scum formation, and minimizes solids buildup. Intermittent biogas sparging mitigates membrane fouling and enhances mass transfer. Downstream, VFAs are recovered through liquid-liquid extraction, simplifying separation and targeting 98% purity suitable for catalytic upgrading to sustainable aviation fuel. The generated VFAs can then be upgraded into jet-range hydrocarbons via ketonization and hydrodeoxygenation.
A preliminary techno-economic analysis (TEA) was conducted for SAF production from the co-digestion of food waste, sewage sludge, and agricultural residues totaling 250 MT/day to assess the system’s viability. TEA results show a minimum selling price (MSP) of $2.22/gallon for SAF, with an estimated fixed capital investment of $33 million and operating costs of $7 million. Co-production of naphtha as a byproduct can further reduce SAF costs. This pathway is economically competitive compared to the average U.S. jet fuel price of $5.71/gallon [5]. Future work will investigate the lifecycle environmental impacts of the technology, and conduct robust optimization to reduce commercialization risk and identify key technological drivers.
References
[1] M. F. Shahriar and A. Khanal, “The current techno-economic, environmental, policy status and perspectives of sustainable aviation fuel (SAF),” Fuel, vol. 325, p. 124905, Oct. 2022, doi: 10.1016/j.fuel.2022.124905.
[2] H. Wu et al., “Sustainable Aviation Fuel from High-Strength Wastewater via Membrane-Assisted Volatile Fatty Acid Production: Experimental Evaluation, Techno-economic, and Life-Cycle Analyses,” ACS Sustainable Chem. Eng., vol. 12, no. 18, pp. 6990–7000, May 2024, doi: 10.1021/acssuschemeng.4c00167.
[3] J. I. C. Lau et al., “Emerging technologies, policies and challenges toward implementing sustainable aviation fuel (SAF),” Biomass and Bioenergy, vol. 186, p. 107277, Jul. 2024, doi: 10.1016/j.biombioe.2024.107277.
[4] M. Atasoy and Z. Cetecioglu, “Bioaugmented Mixed Culture by Clostridium aceticum to Manipulate Volatile Fatty Acids Composition From the Fermentation of Cheese Production Wastewater,” Front. Microbiol., vol. 12, p. 658494, Sep. 2021, doi: 10.3389/fmicb.2021.658494.
[5] “100LL & Jet Fuel Prices at U.S. Airports & FBOs By Region,” Globalair.com. Accessed: Mar. 30, 2025. [Online]. Available: https://www.globalair.com/airport/region.aspx