Quality survey of biodiesel blends sold at retail stations

A quality survey of the biodiesel blends sold in 24 retail stations in March and April 2007 was performed. The main feedstock for the biodiesel blends sold was determined to be soybean oil based. The total acid numbers (TAN) for all of the samples were below 0.3 mg/g, and the derived cetane numbers (DCN) were above 40 for all but one of the samples. The viscosity of all the samples was within the proposed ASTM range for B20. The cold-flow properties were adequate, with the pour point (PP) being below −36 °C for most samples, suggesting the presence of a pour point depressant. However, the oxidative stability for the samples is of concern, with over 45% having an induction period (IP) of less than 6 h. Moreover, the actual blending level of the biodiesel blends generally differed from the blending level on the pump label, and fuel properties varied over a wide range even for the same blend composition.