Low-cost and sustainable electrocatalytic approach for the direct synthesis of biodiesel from waste cooking oil

Biodiesel is an environmentally friendly and biodegradable fuel that can be considered as one of the most promising alternatives to fossil fuels. In this study, the electro-assisted transesterification, by using a graphite pencil mine (PG) electrode, of Waste Cooking Oils (WCO) or frying oils was explored. A maximum Fatty Acid Methyl Esters (FAME) conversion of 96.8 % was obtained at room temperature, applied voltage of 30 V, an oil to methanol ratio of 1:25, and an electrolysis time of 150 min, without co-solvents or additional catalysts. When a nickel-coated PG (PG-Ni) electrode, prepared by cyclic voltammetry, the same yield was obtained in 120 min. The biodiesel quality was confirmed by Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (1H NMR), and GAS Chromatography-Mass Spectroscopy (GC-MS), compiled with EN14214 specifications. The electrode retained over 95 % efficiency after 15 cycles, confirming its stability and reusability. The approach leverages waste valorization, reduces energy consumption, and avoids chemical waste, aligning with circular economy goals.