Biodiesel tested for sterol glycosides and filterability

Berlin, 23th May 2011 - In a broad study, the Association Quality Management Biodiesel reg. Ass. (AGQM) examined the content of sterol glycosides (SG) and acylated sterol glycosides (ASG) as well as the correlation between the SG and ASG content of biodiesel and its filterability. No correlation could be found between poor filterability and a higher content of SG and ASG.

Sterol glycosides and acylated sterol glycosides are natural components of vegetable oils. When producing biodiesel based on these vegetable oils, they are not fully removed and can hence be shown to occur in biodiesel in low concentrations. Due to the low solubility of biodiesel, during storage, they can crystallise and are suspected of causing blockages in the fuel filter.

For the AGQM, this was a reason to systematically examine the SG and ASG contents in vegetable oils and biodiesel in a study. As far as this was possible, at every production plant of the AGQM-members, a sample was taken of the raw material used and the biodiesel produced from it so that conclusions could be drawn as to the extent to which SG and ASG can be removed during the biodiesel process.

It became apparent that the vegetable oils used had a fluctuation range as far as the SG and ASG were concerned with contents of up to 215 mg/kg for SG and 324 mg/kg for ASG, depending on the refinement of the oil in the oil mill. However, both the SG and ASG contents in biodiesel are very low and only exceed 20 mg/kg in rare cases. The investigation into the filterability of the relevant biodiesel showed that a correlation between low filterability and high SG and ASG contents could not be proven.

The complete study can be downloaded here.