This study focuses on the design, optimization, and evaluation of a biodiesel production process involving the transesterification of waste cooking oil (WCO) using a heterogeneous calcium oxide (CaO) catalyst derived from waste eggshells. The work is divided into two main parts. The first focuses on the laboratory preparation, characterization, and performance of the CaO catalyst, while the second translates the experimentally optimized conditions into a process-scale model using Aspen HYSYS to assess industrial feasibility. Waste eggshells were cleaned, dried, ground, and calcined at high temperature to produce the CaO heterogenous catalyst. The catalyst was characterized by Simultaneous Thermogravimetric-Differential Scanning Calorimetry (TG-DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Transesterification experiments were conducted in a batch round-bottom flask reactor where CaO was added to sunflower oil and methanol, and multiple operating parameters were varied to determine the optimal conditions. The catalyst exhibited its best performance after calcination at 900 °C for 2 h. A maximum biodiesel yield of 95 wt.% was obtained at a methanol-to-oil molar ratio (MOMR) of 9:1, reaction time of 2 h, stirring speed of 700 rpm, temperature of 60 °C, and catalyst amount of 3 wt.%. In addition, the eggshell-derived CaO catalyst maintained a biodiesel yield close to 95% over three consecutive reuse cycles, demonstrating good reusability and catalytic stability. The produced biodiesel complied with ASTM standards. Based on these results, the process was then scaled up by simulating a continuous industrial biodiesel production plant using Aspen HYSYS. The model proved practical, achieving a biodiesel purity of 99.85%. Further process optimization, including methanol recovery and heat integration, reduced fresh methanol consumption by 60% and overall energy requirement by 25%. The combined experimental and simulation results demonstrate that energy efficiency and waste valorization enable a biodiesel production pathway that is both environmentally and economically sustainable and aligned with circular economy principles and sustainable development goals.

In this work, the use of a banana peel-derived basic heterogeneous catalyst is investigated for producing biodiesel from sunflower oil. The catalyst is produced by treating dried banana peels at 700 °C under normal atmosphere for 4 h. The reaction parameters were optimized by varying the methanol-to-oil molar ratio (MOMR) and the catalyst-to-oil ratio (CTOR). The highest conversion of sunflower oil to biodiesel (99.4%) was attained after a reaction time of 90 min using an MOMR of 9:1, a catalyst loading of 4 wt%, and a stirring rate of 300 rpm. The catalyst demonstrated good stability, with a yield of 99.4% (±0.28%) obtained over three consecutive runs. No active phase loss was observed during the consecutive reactions, as confirmed by the leaching test. The physical and chemical properties of the formed biodiesel were in good accordance with the American Society for Testing and Materials (ASTM) standards. The kinetic study allowed for the determination of the activation energy (Ea = 58.1 kJ/mol) and pre-exponential factor (A = 7.4 × 10⁷ min⁻¹) of the catalyzed reaction. Additionally, the valorization of waste cooking oil (WCO) (a second-generation feedstock oil) using the waste banana peel-derived catalyst under optimum reaction conditions achieved a yield of 99.1% (±0.14%).