Impact of fatty ester composition on low temperature properties of biodiesel-petroleum diesel blends

Several biodiesel fuels along with neat fatty acid methyl esters (FAMEs) commonly encountered in biodiesel were blended with ultra-low sulfur diesel (ULSD) fuel at blend levels permitted by ASTM D975 (B1-B5) and cold flow properties such as cloud point (CP), cold filter plugging point (CFPP) and pour point (PP) were measured. The objective was to determine whether or not the fatty acid composition of biodiesel affects cold flow properties of blends at levels such as B1 to B5. Statistical methods such as least squares regression and one-way analysis of variance coupled with Tukey's Studentized Range test were applied to the resulting cold flow property data. Statistical analysis revealed that fatty acid profile did not affect cold flow properties at low blend levels unless the biodiesel sample contained a high percentage (>48%) of long-chain saturated FAMEs. Other important conclusions were that variances in cold flow property data at low blend levels (B1 to B2) were minimal and generally statistically equivalent regardless of fatty acid composition. Lastly, application of least-squares statistical regression to CP, CFPP and PP data revealed distinct mathematical relationships between cold flow properties and blend ratio. Specifically, CP was best fit to an exponential decay model whereas PP exhibited linearity and CFPP provided the highest R2 values when fitted to polynomial equations. In summary, this study demonstrated that in most cases feedstock selection for biodiesel fuel had minimal impact on cold flow properties at the blend levels permitted by ASTM D975, the US standard specification for diesel fuel oils.