Waste Cooking Oil-Derived Methyl Ester Sulfonate for Enhanced Oil Recovery: A Short Review

Abstract

The increasing demand for sustainable chemical enhanced oil recovery (EOR) has encouraged the development of bio-based surfactants from renewable and low-cost feedstocks. Methyl ester sulfonate (MES) derived from waste cooking oil (WCO) is a promising alternative because of its surface activity and potential contribution to waste valorization. This study presents a structured narrative review linking WCO characteristics, transesterification, MES synthesis, and EOR performance. The reviewed studies indicate that free fatty acid content, moisture, oxidation products, and impurities strongly affect FAME quality and subsequent MES synthesis. Alkali-catalyzed transesterification was commonly reported at 60–65 °C using methanol-to-oil molar ratios of 6:1–9:1 and approximately 1 wt% catalyst. Continuous SO₃-based sulfonation generally provides higher process efficiency and MES quality, whereas NaHSO₃-based processes offer simpler laboratory-scale operation. Reported MES-based systems showed substantial reductions in oil–water interfacial tension and incremental oil recoveries of approximately 25–69% under different experimental conditions. However, direct comparison remains limited by the small number of studies covering the complete WCO–FAME–MES–EOR pathway and by differences in formulations and test conditions. Future studies should integrate standardized feedstock characterization, FAME and MES quality assessment, and reservoir-relevant testing within the same experimental framework.