Abstract
We investigated the composition and impurities of waste cooking oil discharged from households and restaurants. Though the characteristics of oils discharged vary greatly between individual sources, we verified that the process of collection and accumulation results in homogeneous oil mixtures. We analyzed the correlations of (1) acid values and free fatty acids, and (2) iodine values and saturated fatty acids as indices of the deterioration state and major composition of waste oil. Furthermore, concerning the relationship of waste oil quality and its conversion to fuel, we confirmed that in ester conversion and washing processes (1) the flash point decreases and kinematic viscosity improves, (2) the fatty acid constitution and iodine value is maintained, and (3) free fatty acids, acid values, metals, and inorganic chlorines decrease. In addition, we determined through our analysis that the residual glyceride quantities in the oil, a primary factor in biodiesel fuel quality, are affected by differences in kinematic viscosity, CFPP and carbon residue (based on a 10% distillation residue) . In order to promote biodiesel fuel conversion, a standard for waste cooking oil was determined that consists of acid value, iodine value, saturated fatty acid, water content and impurities.
