ASTM approves modified biodiesel specification

25 July 2012

In a meeting held last week, the ASTM Committee on Standards approved a new voluntary No. 1-B grade for biodiesel (B100). The specification was passed by the ASTM D2 Committee on Petroleum Products and Lubricants this past spring.

ASTM D6751, the ASTM standard for pure biodiesel (B100) blending stock, was modified to create a new voluntary No. 1-B grade. The new grade introduces new controls for certain biodiesel contaminants, to improve the low temperature operability of biodiesel and prevent fuel filter clogging that has been occasionally encountered with biodiesel fuels.

The specification values of the current standard will become the No. 2-B grade in D6751 without change. Producers or blenders can continue to utilize the current specification under the No. 2-B grade, or they may opt to use the more stringent No 1-B grade.

The finished blended fuel standards—D975 for diesel fuel up to 5% biodiesel (B5), D7467 for B6-B20 applications, and D396 for heating oil up to 5% biodiesel—do not change. B100 used for D975, D7467, and D396 must continue to meet D6751 (either the No. 1-B or the No. 2-B grade) prior to blending.

The interest in creating No.1-B specification was triggered by cases with ultra low sulfur diesel fuel experiencing filter clogging above the cloud point of the finished blend, which mostly occurred with low aromatic No. 1 type diesel blends. The voluntary No. 1-B grade includes new controls for monoglycerides—the biodiesel contaminants that have been implicated in filter clogging in the field with ULSD. Monoglycerides are limited in the new No. 1-B grade to 0.40% mass maximum, while the Cold Soak Filtration Time is limited to 200 s year around.

The choice of the No. 1-B and No. 2-B designations were selected to make the standard similar to the current mode of operation with No. 1 and No. 2 diesel fuel, explains the National Biodiesel Board. Most users utilize No. 2 diesel fuel, but if they experience fuel filter clogging they can switch to No. 1 diesel fuel, use additives or other means to prevent the problem. The same philosophy applies to the No. 1-B and No. 2-B biodiesel specification—most users will continue to utilize the No. 2-B biodiesel but if unexpected filter clogging is experienced, No. 1-B can be used for blending.

The modified version of ASTM D6751 containing the new No. 1-B grade will be released for public use later this summer after editorial review.

Source: National Biodiesel Board