Facile fractionation of spent coffee grounds into sustainable aviation fuel-relevant streams using methanol and potential endogenous alcohol–glycerol solvent mixtures

Authors: ACQUAL, CHRISTOPHER - Rowan University; Jones, Kerby; Wyatt, Victor; Garcia-Negron, Valerie; ABOAGYE, EMMANUEL - Princeton University; BAE, WO BIN - Rowan University; SMALL, ISHIMIAH - Rowan University; KLEISSLER, JACK - Rowan University; BIN BAE, WO - Rowan University; STANZIONE III, JOSEPH - Rowan University; JANG, JUN HEE - Rowan University

Submitted to: The Royal Society of Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2026
Publication Date: 3/6/2026
Citation: Acqual, C., Jones, K.C., Wyatt, V.T., Garcia-Negron, V., Aboagye, E., Bae, W., Small, I., Kleissler, J., Bin Bae, W., Stanzione III, J.F., Jang, J. 2026. Facile fractionation of spent coffee grounds into sustainable aviation fuel-relevant streams using methanol and potential endogenous alcohol–glycerol solvent mixtures. The Royal Society of Chemistry. https://doi.org/10.1039/D5GC06813D.
DOI: https://doi.org/10.1039/D5GC06813D

Interpretive Summary: The increasing demand for sustainable aviation fuel (SAF) production in the transportation sector urges the need for economically viable new feedstocks. SAFs are commonly made from natural oils such as soybean oil but their supply is limited. New routes from other biomass resources including agricultural residues consisting of lignocellulosic resources are being developed. Major challenges in scaling SAF production are determining additional biomass feedstock to increase supply and separating the main biomass components (i.e., carbohydrates, lignin, and lipids) to maximize fuel production in a cost-effective manner. Spent coffee grounds (SCG) is a readily available and abundant biomass, mainly produced as waste from coffee brewing, with up to 50% carbohydrate content. In this study, an alcohol-based fractionation (solvolysis) strategy requiring only a single reactor was evaluated on SCG, achieving high retention of carbohydrates (>75%) along with effective delignification (>67%) and delipidification (>92%). Comparisons between a conventional external alcohol solvent (methanol) versus using processing intermediates as alcohol co-solvents (ethanol and glycerol) showed the endogenous co-solvent systems performed better while requiring less energy and enabling safer operations to produce SAFs at a lower cost. The endogenous co-solvent system required a reactor pressure that was 59% lower and 26% cheaper than methanol solvolysis. These efforts help optimize biomass processing for different applications, and particularly for SAFs, help reduce carbon emissions and lower fuel costs of aircraft engines without requiring modification.

Technical Abstract: Spent coffee grounds (SCG), an abundant lignocellulosic biomass waste, offer potential for sustainable aviation fuels (SAF) production due to their major components of carbohydrates (50%), lignin (30%), and lipids (8%), with efficient fractionation being the main challenge. This study presents an alcohol-based solvolysis strategy for deconstructing SCG into SAF-relevant fractions while enabling the use of ethanol and glycerol as endogenous co-solvents. Methanol solvolysis achieved high retentions of glucan (99.5% at 180 °C and 98.0% at 200 °C), mannan (99.0% at 180 °C and 79.0% at 200 °C), and galactan (93.0% at 180 °C and 78.0% at 200 °C), with delipidification (>95.0%) and delignification (>52.0%). The ethanol/glycerol (1:1 v/v) co-solvent at 200 °C demonstrated comparable glucan and mannan retentions of 88.0% and 76.0%, with delignification (67.0%) and delipidification (93.0%). All tested solvent systems yielded a combined 61-66 wt% of SAF-convertible lipid, lignin, and carbohydrate fractions, each suitable for direct integration into established catalytic upgrading pathways. Despite the comparable fractionation efficiency, the endogenous solvent systems reduced autogenous pressure to 15.6 bar, 59% lower than neat methanol solvolysis, enabling safer, more energy-efficient biorefinery operation. Techno-economic analysis shows superior performance for co-solvent systems, with ethanol/glycerol achieving a minimum selling price (MSP) of $1.43/kg and methanol/glycerol achieving $1.64/kg, which are 30% and 20% lower than methanol solvolysis ($2.05/kg) while delivering enhanced solvent circularity and operational safety.