Enhancing biodiesel production efficiency with industrial waste-derived catalysts: Techno-economic analysis of microwave and ultrasonic transesterification methods

• The catalyst derived from industrial waste produces high-quality biodiesel. • The catalysts from industrial waste are recyclable, cheap, and eco-friendly. • Using microwave and ultrasonic enhance the biodiesel economics and production. • Recycling industrial wastes to valuable products is vital for the environment. Biodiesel is a low-emission, environmentally friendly, and renewable alternative to diesel fuel. Conventional transesterification, the most common method for biodiesel production, has several drawbacks, including high temperature, high reactant consumption, and extended reaction times. Homogeneous alkaline catalysts, frequently used in biodiesel synthesis, present issues such as high cost, limited recyclability, and efficiency concerns. Herein, we technically and economically evaluate new transesterification approaches, such as ultrasonic and microwave methods, utilizing a recyclable heterogeneous catalyst derived from industrial waste. Our findings indicate that the biodiesel produced meets high technical specifications and demonstrates the high efficiency of the low-cost heterogeneous catalyst in the new transesterification methods. The yield quantity for the three methods, microwave, ultrasonic, and conventional, was 97.4%, 96.9%, and 96.6%, respectively, and the produced biodiesel standards had excellent quality and meet international standards (ASTM-6751). The microwave and ultrasonic methods reduced reaction time by 99.5 and 83.3%, respectively, as well as the amount of methanol by 50% and the amount of catalyst by 50 and 75%, respectively, proving the high positive impact of new techniques on biodiesel production. Financial indicators such as net income, return on investment, net present value (NPV), and profitability index showed higher values for microwave and ultrasonic methods compared to conventional transesterification, highlighting the significant profitability of these methods.