Efficient recovery and reuse of heterogeneous catalysts is vital for the economic viability of catalytic technologies. In this work, three catalyst recycling methods – filtration, centrifugation and magnetic extraction – were systematically compared for the first time on a single catalyst over five cycles in a biodiesel production. CaO-based magnetic catalyst was synthesized from calcium carbide slag (CS) and Fe3O4 by wet impregnation followed by calcination at 600 °C for 2 h (CS-Fe-600). Under optimal conditions (5 wt% catalyst loading, the oil to methanol molar ratio = 1:12, reaction temperature 65°С and time 2 h), the biodiesel yield was 99 % after the first cycle. After five reuses, filtration maintained the highest performance (90 % yield, 81 % recovery), centrifugation demonstrated moderate stability (82 % yield, 67 % recovery), while magnetic separation led to rapid catalyst loss (84 % yield, 28 % recovery). The catalyst was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray Fluorescence (XRF), Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray (EDX) and thermogravimetric analysis (TG). According to XRD, the catalyst underwent phase transformations during reuse, including a decrease in CaO content from 50.3 wt% to 13–18 wt% after the first cycle and the subsequent formation of Ca(OH)₂ and calcium diglyceroxide as the main phases.