Fatty acid methyl ester (FAME) was produced from waste cooking oil (WCO) utilizing eggshells derived solid base catalyst. Eggshells derived multi modal CaO (MM-CaO) also provides a cost-effective way for the preparation of green fuel. The nano-scaled MM-CaO was prepared using ball milling followed by calcination at 800 °C for 2 h form eggshells powder. The characterization of calcined powder was executed by XRD, EDX, SEM and FTIR techniques. Diffractogram of MM-CaO showed cubic crystal structure and presence of calcium, carbon and oxygen was confirmed by EDX. The morphology of MM-CaO was revealed by SEM having bandgap energy (3.02 eV) which declared MM-CaO as photoactive in solar range. Catalytic transesterification process furnished 75.2% yield, whereas in photocatalytic process, 86.8% yield was obtained at optimum conditions (temperature 50 °C, reaction time 180 min and 1.5 g catalyst dose). The FAME formation was monitored by GC and FTIR analysis. Physiochemical properties of produced biodiesel were also determined and equated with standards. Results depicted that MM-CaO is highly efficient for conversion of WCO to biodiesel.