The CaO-SiO2 catalyst is a type of heterogeneous catalyst widely used in biodiesel production. Modifying the CaO-SiO2 catalyst by adding Fe2O3 can enhance its catalytic activity, surface area, and increase the number of active sites, resulting in a higher biodiesel yield. The aim of this study was to synthesize the CaO-SiO2/Fe2O3 catalyst from blood clam shells, coconut husks, and Fe2O3 powder …