Life cycle assessment of biodiesel synthesis from waste cooking oil using bifunctional heterogeneous catalyst

Abstract The development of renewable energy sources is important in order to achieve the United Nations Sustainable Development Goals (SDGs). Waste cooking oil (WCO) is a promising feedstock for biodiesel production through transesterification. Heterogeneous bifunctional catalysts offer a sustainable alternative to conventional homogeneous bases such as NaOH and KOH. Among them, ferrimagnetic CaO–Fe 3 O 4 provides dual acid–base functionality, enabling efficient catalysis with facile magnetic recovery and reuse. This study evaluated the environmental performance of biodiesel synthesis from WCO using homogeneous and heterogeneous catalysts through life cycle assessment (LCA), with biodiesel from virgin cooking oil (VCO) as a benchmark. A cradle‐to‐gate system boundary was applied, and 10 MJ of biodiesel was defined as the functional unit. Environmental impacts were assessed using midpoint and endpoint indicators. The results showed that electricity consumption was a notable contributor to overall emissions in systems employing heterogeneous catalysts. Sensitivity analysis of the CaO–Fe 3 O 4 ‐catalyzed WCO system showed that partial substitution of nonrenewable electricity with 50% renewable electricity reduced climate‐change‐related emissions by 35%. Overall, the results highlighted the environmental advantages of heterogeneous bifunctional catalysts for WCO biodiesel, particularly when integrated with renewable energy inputs.