High-Efficiency Biodiesel Production Using ZnO-Modified Starfish-Based Catalysts

This study introduces a novel approach to biodiesel production by repurposing starfish, an abundant marine waste, as a sustainable catalyst material. Starfish, primarily composed of Ca-Mg carbonate, were calcined to produce calcium oxide (CaO) and magnesium oxide (MgO), which were subsequently doped with varying zinc loadings through hydrothermal treatment. This innovative use of marine waste not only addresses environmental concerns but also provides a cost-effective catalyst source. Among the tested compositions, the catalyst doped with 10 wt% Zn achieved the highest biodiesel yield of 96.6%, outperforming both lower and higher Zn loadings. Zinc incorporation significantly improved the catalyst’s surface area, pore volume, and active site density, as confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) surface analysis. These enhancements facilitated a biodiesel yield of 96.6% within 10 h, a substantial increase compared to the undoped catalyst (86.5%) under identical conditions. Reusability tests further confirmed the catalyst’s high activity over three consecutive cycles, with yields of 96.6%, 94.2%, and 86.5%, respectively, while SEM-EDS analysis demonstrated effective Zn retention after repeated use. This study demonstrates a pioneering strategy for transforming marine waste into a high-performance catalyst, paving the way for sustainable biodiesel production.