ASTM begins to pass new biodiesel specs

By Ron Kotrba | January 17, 2008
Coming out of the ASTM meeting in Phoenix in December, voting biodiesel advocates were cautiously optimistic but recognized there was still work to do in order to approve a series of new biodiesel and bio-related diesel specifications.

Stu Porter, a technical analyst for BBI Biofuels Canada and a voting ASTM member, told Biodiesel Magazine the good news: After a great deal of effort and discussion, the ballots proposing to allow 5 percent biodiesel into specifications for petroleum diesel (D 975) and heating oil (D 396), and a ballot for a stand-alone B6 to B20 biodiesel blend spec passed out of subcommittee and are moving on to the Main D2 ballot. This means biodiesel meeting its own spec, D 6751, is one step closer to acceptance and invisible integration into petroleum fuel supplies. At least D 975 and D 396 will allow up to 5 percent biodiesel.

While the news is promising, there is a pending stipulation that the passage in main committee hinges on. The three ballots-B5 in D 975, B5 in D 396 and the stand-alone spec for B6 to B20-are all linked to another important test method being balloted: the cold soak filtration test method. It is devised to prevent materials, such as unconverted monoglycerides and diglycerides, from falling out of solution causing filter plugging and damaging biodiesel's reputation as a transportation fuel. In December 2006, the B5 in the D 975 and D 396 ballots was voted down because of three persuasive negatives, Porter said. All three came from refiners concerned about biodiesel quality issues and wider fuel-supply contamination issues. "There is currently nothing in the specification protecting against those occurrences," another ASTM source said. "So it was determined that the negatives [against B5 in D 975 and D 396] would be withdrawn pending a successful addressing of that problem, and the change must be incorporated into D 6751 to deal with that issue." In order to appease those who voted the B5 and B6 to B20 specs down, the specs became linked to the cold soak filtration method in the Subcommittee 14 Task Group.
The cold soak measure tries to emulate conditions in which substandard biodiesel has been known to precipitate material out of solution. The fuel is chilled, filtered and measured for settled material. "The cold soak filtration method was the solution in Minnesota and was accepted by the suppliers to Minnesota prior to the reinstatement of the B2 mandate in February 2006," Porter said.

Subcommittee 14 failed to pass the cold soak method in December. "Several different parts of the method had been investigated as possible sources of imprecision in the test method," the ASTM source said. Precision testing done under slightly different conditions and the lack of members seeing eye-to-eye led to the method's omission this go-round. Which filter to use, which filter holder, cooling rates, how to rewarm the fuel after being chilled and other discrepancies also contributed to the imprecision, and therefore the method's inability to pass it. The next several months will involve significant work on honing the proposed method so that it-and the specs linked to it-can become part of ASTM fuel standards.

One balloted item did pass all committee levels and will be incorporated into the standard in early 2008. The Particulate Contamination of Biodiesel and Biodiesel Blends test method is basically a modified D 6217 spec, the particulate contamination test for diesel fuel. Since petroleum contaminants differ from those that may pollute biodiesel, methyl-ester-specific attributes were incorporated into a test method similar to D 6217. At press time, the new method hadn't been assigned a number.
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