The depletion of resources and increase in demand for fossil fuel raise concerns as it is natural and non-renewable. Therefore, it will cause limitation on its availability and continuous reduction. This issue has led to the search for more economic, sustainable, and environmentally friendly alternatives which is biodiesel. The major drawback that reduces the possibility of biodiesel commercialization is the high cost of oil feedstock as it covers 75 of its total production cost. The waste cooking oil is used as feedstock in continuous transesterification as it is the primary option to lower the cost of biodiesel production. Biodiesel can be prepared using waste cooking oil and catalyst through transesterification reaction. In this research, the focus is on the utilization of chicken and quail waste eggshell to synthesize highly active Calcium Oxide (CaO)-based heterogenous catalyst with montmorillonite clay to catalyze efficient conversion of waste cooking oil to biodiesel. The formation of CaO/montmorillonite catalyst was confirmed based on the outputs from X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The physio-chemically characteristics of catalysts exhibited a BET surface area from the ranging from 9.2-9.5 m2/g and presence of around 87 of elemental calcium as constituent through XRF characterization. In addition to this, high-performance liquid chromatography (HPLC) analysis is used to determine the conversion of biodiesel using conventional and microwave heating method which revealed a maximum biodiesel production yield of 98. This optimum biodiesel yield was obtained at reaction temperature, molar ratio of waste cooking oil to methanol, and catalyst amount of 60 ºC, 2 h, 1:12, 2.5 wt. and 5 wt. for both eggshells, respectively. © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/)