2009 Quality survey of retail biodiesel blends in Michigan

A fuel quality survey of biodiesel blends collected in June 2009 from 26 Michigan retail stations was performed, 8 months after the publication of ASTM D7467. Measured blend levels were not consistent in stations where pump labels indicate specific biodiesel blend levels. Fatty acid methyl ester (FAME) analyses revealed that majority of the samples are soybean oil-based (SBO) biodiesel. Full compliance with the ASTM D7467 requirements for kinematic viscosity and flash point (FP) were observed with the biodiesel blends; all but one for cetane number (CN). Barely half of the samples were able satisfy the total acid number (TAN) specification with select samples reflecting as high as 1.6 mg KOH/g. The most pressing is that only 45% were able to meet the 6 h induction period (IP) requirement; out of those that did not qualify 42% are even low blends hinting the degraded quality of the biodiesel component. Inconsistencies on the expected correlations of the tested properties were evident, suggesting that additives may be present in many samples. When compared with results from a similar survey in 2007, the properties of the 2009 samples are even poorer, indicating poor observance of fuel standards by the producers.