Flash-catalytic upcycling of olive pomace into crystalline graphene nanosheets for a low-carbon route toward sustainable energy materials

Official URL: https://dx.doi.org/10.1016/j.est.2026.121648

The sustainable valorization of agricultural residues into high-value carbon materials represents a critical step toward circular and low-carbon manufacturing. In this study, olive pomace, a regionally abundant agro-industrial by-product, was upcycled into crystalline graphene nanosheets (GNS) through a rapid flash catalytic carbonization process operating within 5 s. The developed two-step route, combining flash pyrolysis and Fe-catalyzed graphitization, enabled the transformation of disordered amorphous carbon into a well-ordered hexagonal lattice with an interlayer spacing of 0.23 nm and a graphitization degree of approximately 62%. The resulting GNS exhibited a multilayered (below 50 layers), porous architecture, high thermal stability up to 1000 °C, and enhanced electrical conductivity of 2.55 S/m. Electrochemical evaluation of symmetric supercapacitors demonstrated an energy density of 70 Wh kg−1 and 80% capacitance retention after 1000 cycles, confirming excellent charge-storage stability and durability. Importantly, a life-cycle assessment based on industrial-scale modeling revealed that the carbon footprint of the upcycled GNS was reduced by 99.8% compared with graphene produced via conventional chemical oxidation routes. This work provides a scalable, energy-efficient, and environmentally compatible pathway for converting biomass waste into functional two-dimensional materials.