Effects of storage under different conditions on the fuel properties of biodiesel admixtures derived from waste frying and canola oils

This study investigates the effects of storage conditions on the properties of transesterified methyl ester using waste frying (WFME) and waste canola (WCME) and their blends. Biodiesel samples were stored for 24 months at ambient temperature and also at 40 °C, and properties including oxidative stability, acid value, flash point, kinematic viscosity, density, cloud point (CP), and pour point (PP) were periodically measured. The variation of kinematic viscosity and density within a range temperature of − 10 to 300 °C were examined during the storage periods. The analysis showed that both viscosity and density increase because of the increase in the concentration of WFME in the blend, and both of them decrease as temperature increases. It is found that blending WCME with WFME has a significant improvement on the cold flow properties of WFME. Furthermore, oxidative stability and flash point were significantly reduced upon extended storage whereas acid value, kinematic viscosity, and density were increased by only small increments. Moreover, the CP and PP of blends were also affected by extended storage when the WCME concentration in those mixtures was under 35% by volume. In this work, 19 general correlations were presented for estimating kinematic viscosity, density, CP, and PP of the blends at several temperatures. These correlations depend on the temperature, volume fraction of WFME, storage temperature, and storage periods. The estimated values of biodiesel properties are in good agreement with the experimental data of this study and literature. The developed equations could be used as universal formulas to predict the biodiesel properties.