Serious problems in the current decades are the ensuring of enough energy supply and mitigating the consequences of global warming. Considered as a substitute for exhaustible fossil fuels in recent years, biodiesel may help to lower world temperature and considered as renewable source of energy. In this work, the feasibility of using CaO nano catalyst derived from falling willow leaves extraction, with microwave assistance as a heating source to produce biodiesel from waste cooking oil was investigated. We investigated the effects of fundamental parameters including the amount of microwave power, the ratio of methanol to oil, the time and temperature of the reaction, and the amount of catalyst used. The results show that the best yield, 96%, was reached at 65°C in 20 minutes with a3 wt.% catalyst loading and a 70wt.% methanol: oil ratio. The activation energy for the catalyzed transesterification process, which was 24.266kJ/mol, indicates that the reaction is under chemical control. The importance of this study goes beyond the academic aspect, as it represents a practical model for biodiesel production at the industrial level by utilizing biomass waste as catalysts and inedible oils as raw materials, using microwave-based heating systems, which contributes to the application of green and environmentally friendly chemistry. The study also relies on the use of economical raw materials that are not suitable for human consumption, utilizing biomass waste to produce biofuel, which supports environmental sustainability and the sustainable management of biomass waste, and enhances modern and advanced research in the field of biofuel production.