(680a) End-to-End Process Framework for SAF Production Via Lignin-First Process Integrating Thermochemical and Electrochemical Routes

To enable a complete shift to sustainable aviation fuels (SAF), it is crucial to establish strategies that utilize various carbon sources. Among these, lignocellulosic biomass is as a promising feedstock because of its abundance and carbon neutrality. Notably, lignin accounts for up to 25% of biomass¹, yet it has traditionally been underutilized, usually burned on-site for process heat. Therefore, valorizing lignin as a feedstock is essential to fully unlock the potential of lignocellulosic biorefineries. Reductive catalytic fractionation (RCF) is a lignin-first biorefining approach consisting of two main steps: 1) solvolysis-based depolymerization of lignin and 2) hydrogen-assisted stabilization of the resulting fragments¹. This process enables early-stage lignin separation, preserving its chemical reactivity and allowing downstream upgrading. However, this approach faces challenges such as reactor capital cost, high energy requirements and solvent consumption^2,3, suggesting opportunities for process optimization

In this study, we conducted a comprehensive analysis of the lignin-to-jet fuel process based on RCF with ethanol co-production from carbohydrates, aiming for commercial-scale implementation. The process covers the entire system from feedstock handling to utility generation, allowing an end-to-end evaluation of the biorefinery. Given the limited database for lignin-based process design, we developed a simplified mechanistic model based on the B-O-4 ether bond cleavage mechanism, which is the most dominant linkage in lignin⁴. The model incorporates estimated physicochemical properties derived from the structure to predict key lignin-processing parameters, such as hydrogen and heat requirements. Sensitivity analyses and comparisons with expected case scenarios were conducted to provide strategic insights into detailed biomass utilization guidelines. Among the analyzed cases, the optimal configuration using representative values from pilot-scale data and the literature- demonstrated approximately a 35% increase in economic performance and a 70% reduction in the required heat utility compared to the baseline process.

To complement the thermochemical route, we present our team’s electrochemical biorefinery approach and discuss various experimental demonstrations, including electrochemical fractionation and jet fuel production(deoxygenation)⁵. Multiple scenarios were evaluated to provide additional insights into the optimal design of the system. In the case of deoxygenation, a techno-economic analysis across three scenarios-our lab-scale base case under surfactant-assisted conditions, a literature-based case under comparable feedstock conditions-, and an optimistic target case - showed that the base-case MSP of the electrochemical route is ~3 times higher than that of thermochemical route, but narrows to 1-1.5 times under optimized electrolyzer conditions (FE: 90%, current density:1A/cm2). The environmental impact under optimal case also remains slightly higher for the electrochemical route. These limitations stem from the early-stage nature of the electrochemical route; for example, the current deoxygenation process does not efficiently convert dimers/oligomers into higher-value products. Nevertheless, electrochemical approaches offer advantages, such as mild operating conditions and compatibility with hydrogen-based systems, suggesting strong potential for future improvement as the technology matures.

By combining insights from both methods, we propose a system-level framework for an integrated, energy-efficient, and scalable SAF production process. This study provides a foundation for lignin utilization strategies and highlights the complementary roles of thermochemical and electrochemical routes in future biorefineries.

1. Renders, T., Van den Bossche, G., Vangeel, T., Van Aelst, K., & Sels, B. (2019). Reductive catalytic fractionation: state of the art of the lignin-first biorefinery. Current opinion in biotechnology, 56, 193-201.
2. Bartling, A. W., Stone, M. L., Hanes, R. J., Bhatt, A., Zhang, Y., Biddy, M. J., ... & Beckham, G. T. (2021). Techno-economic analysis and life cycle assessment of a biorefinery utilizing reductive catalytic fractionation. Energy & Environmental Science, 14(8), 4147-4168.
3. Liao, Y., Koelewijn, S. F., Van den Bossche, G., Van Aelst, J., Van den Bosch, S., Renders, T., ... & Sels, B. F. (2020). A sustainable wood biorefinery for low–carbon footprint chemicals production. Science, 367(6484), 1385-1390.
4. Ralph, J., Lapierre, C., & Boerjan, W. (2019). Lignin structure and its engineering. Current opinion in biotechnology, 56, 240-249.
5. Wang, J., Han, M. H., Langie, K. M. G., Won, D. H., Lee, M. Y., Oh, C., ... & Lee, W. H. (2025). Understanding the Dynamics Governing Electrocatalytic Hydrodeoxygenation of Lignin Bio-Oil to Hydrocarbons. Journal of the American Chemical Society.