Recent Advances in Biodiesel Synthesis from Waste Cooking Oil Using Magnetic Nanoparticle-Based Catalysts: A Brief Review

Biodiesel is known as one of the most prospective renewable fuels targeting to replace fossil-based diesel particularly when derived from waste cooking oil (WCO) which is cheap and non-food feedstock. Generally, homogeneous catalysts are used for biodiesel synthesis, which can lead to various difficulties such as separation issues and wastewater generation as well as saponification at sin higher free fatty acids (FFA) concentration.

 Heterogeneous magnetic nanocatalysts have gained considerable attention due to their high catalytic efficiency, ease of separation via magnetic fields, and reusability. This review explores the progress in the use of magnetic nanoparticles (MNPs) metal oxides, spinel's, and bio-derived nanocatalysts in biodiesel synthesis via transesterification and esterification reactions. Emphasis is placed on catalysts prepared with iron-based cores (Fe₂O₃, Fe₃O₄) doped or functionalized with metals such as Ca, Cu, Ni, and Co, or immobilized enzymes such as lipases. Recent studies from 2020 to 2025 are critically evaluated to catalyst composition, synthesis methods, and performance metrics (yield, reaction conditions, reusability). This approach can contribute to waste recycling and potentially reduce carbon emissions, in alignment with the Sustainable Development Goals.