Biodiesel Fuel Filter Blocking Problems Involving Diesel Fuels Blended with Biodiesel

01 Apr 2009

With the increased use of biodiesel blended into refined diesel fuels, there are an increasing number of fuel filter clogging incidents involving diesel fuels blended with biodiesel.

The biodiesel fuel filter blockage problem is occurring even though the biodiesel’s cold flow properties (CFPP) do not predict the likelihood of filter clogging problems. The growing numbers of diverse feed-stocks used for biodiesel can increase the risk of filter problems.

Periodical sampling & testing of fuel during storage prevents possible damage to filters and down-time for commercial and private vehicles. Intertek laboratories test many types of biodiesel, encountering several root-causes for filter clogging; the presence of sterol glucosides and/or bacteria.

Link between Sterol Glucosides and Filter Blockage:

There appears to be a relationship between filtration problems and the presence of sterol glucosides. Testing indicates that as the level of sterol glucosides increases, so Filter Blocking Test (FBT) values increase. The presence of sterol glucosides at problematic double-digit ppm levels can lead to the formation of a cloudy haze in biodiesel, even at room temperature.

Link between Bacterial Growth and Filter Blockage:

Bio-diesel has an affinity for water and easily absorbs moisture from the atmosphere. This water then supports microbiological growth in fuel storage tanks. At low levels microbes usually don’t make a major impact on fuel functionality, but if left unchecked, bacteria growths can block fuel filters.

To learn more about these problems, and the steps biodiesel producers and consumers can take to protect themselves, please contact Intertek.