A new Cold Soak Filtration Test method for B100, which ASTM committee members had passed months ago, finally made it out of a Committee of Standards review process and has received an official number – ASTM D 7501. According to Stu Porter, chair of the Subcommittee 14 Biodiesel Cleanliness Task Group, the new method will be published later in April, after which it will become official. The task group Porter heads up was responsible for developing a new CSFT method to replace the current, flawed method in the annex. Porter also adds that the new precision will be balloted in late April as well.

The CSFT method currently in effect was developed as a result of the Minnesota experience in 2005-2006 of statewide filter cloggings shortly after a state B2 mandate was triggered. The CSFT was developed as an attempt to keep contaminated biodiesel – or biodiesel laden with sterol glucosides, mono and di glycerides, metals, soaps, water – out of the marketplace. Those contaminants can react in such a way to cause a “snow-globe” effect wherein precipitates fall out of solution from the fuel at temperatures above the cloud point. However, the precise mechanisms behind how the contaminants react with one another to cause precipitate formation above the cloud point are still largely unknown.

The main difference between the first CSFT and the recently named ASTM D 7501 is that the former method doesn’t take into account B100 that changes states of matter during the chill. The first CSFT was largely developed around soy biodiesel. The new method will contain a separate set of conditions for biodiesel that changes state during chill. If the sample becomes solid during cool down, it will be given a four-hour warm up time instead of two hours. Also, instead of simply warming the fuel up on the bench, it will be warmed to 25 degrees C to ensure there are no temperature gradients.