Characterization of Biodiesel from Alkaline Refinement of Waste Cooking Oil

Abstract

The waste cooking oil (WCO) is a low cost and prospective feedstock with no competitive food uses for biodiesel production, but the yield and quality have been greatly affected by impurities.  This study examined the chemical and fuel quality of biodiesel of both WCO and alkaline treated WCO.  The transesterification process using the alkaline treated cooking oil (ACO) methanol and sodium hydroxide as catalyst followed the Association of Officials of Analytical Chemists (AOAC) techniques. The pH values between 7.27 and 8.65 were found for alkaline treated cooking methyl ester (ACME), alkaline treated cooking oil (ACO) and WCO. Density of ACME, ACO and WCO varied between 0.89 and 0.93 (g/cm3). The fatty acids found were benzoic acid (3.77%), octanoic acid (8.35%), and palmitic acid (75.02%) – most abundant. Comparison of results with the American Standard for Testing Materials (ASTM) values showed quality enhancements of ACO in physicochemical and fuel properties over WCO. The biodiesels from ACO have enhanced emulsification, fuel and free fatty acids qualities over the WCO, showing the refinement methodology of WCO has overall improvement in the biodiesel purity and quality against the previous conflicting reports.