Holistic Valorization of Spent Coffee Grounds: Integrated Production of Biochar-Supported Catalysts and Green Diesel

The increasing demand for sustainable fuels and the transition toward a circular economy have intensified interest in the valorization of agro-industrial residues as renewable feedstocks. In this study, an integrated approach is investigated for the utilization of spent coffee grounds (SCGs) for the production of green diesel via selective deoxygenation (SDO), combining oil extraction with the development of biochar-supported catalysts.

Coffee oil was initially extracted from SCGs, while the residual biomass was converted into biochar through pyrolysis and subsequently used as a support for catalyst preparation. Nickel-based and bimetallic Mo–Ni catalysts were synthesized using different preparation methods and evaluated for their catalytic performance.

The deoxygenation reactions were carried out under high-pressure hydrogen conditions, and the resulting liquid products were analyzed using gas chromatography–mass spectrometry. The results demonstrated that catalyst composition and support properties significantly influence both activity and selectivity. In particular, the bimetallic Mo–Ni catalyst supported on appropriately treated biochar exhibited enhanced performance, achieving up to 65% yield of hydrocarbons in the diesel range.

The improved catalytic behavior is attributed to the physicochemical properties of the biochar support, which affect metal dispersion and reaction pathways. These findings highlight the importance of catalyst design in optimizing SDO processes for renewable fuel production.

Overall, the study demonstrates the feasibility of converting SCGs into green diesel through an integrated process that combines waste valorization with catalytic upgrading, contributing to the development of sustainable fuel production systems within the framework of the circular economy.