Buyer beware: What blend of biodiesel is in your tank?

By Sarah Smith | April 15, 2008
Small-scale fuel retailers are often inaccurately advertising biodiesel blends, a recent study concluded. Conducted by researchers at the Woods Hole Oceanographic Institution in Massachusetts, the study is the second in four years that found incorrectly calibrated biodiesel blends.

The Woods Hole study found that a B20 blend was actually 20 percent biodiesel in only 10 percent of stations sampled, while remaining samples varied from 10 percent to 74 percent biodiesel. The study, from which results were released Feb. 27, sampled pure biodiesel and blends from more than 20 distributors and small retailers across the United States.

The wide variance is problematic to consumers and their vehicle engines, said Woods Hole chief researcher Chris Reddy. His study was a companion to one conducted in 2004-2005 by the National Renewable Energy Laboratory in Golden, Colo., which found that large-scale retailers were experiencing the same blending inaccuracies. Reddy said when blends deviate to the higher ranges, such as B74, it could damage gaskets and hoses in older vehicles. Researchers concluded the variance stemmed from mathematical errors, measurement mistakes or inadequate mixing. Reddy attributed the error rate to splash blending-pouring the two fuels together into a container. Because biodiesel is denser than petroleum-based fuel, Reddy said it has a tendency to settle to the bottom of a container if not properly mixed.

According to the National Biodiesel Board, fuel-grade biodiesel must be produced to strict industry specifications, such as ASTM D 6751, to ensure proper performance. Each state government regulates its fuel standards, but regulations aren't uniform from state to state. The NBB is currently working with each state to catalog information regarding their ability to regulate biodiesel, adopt standards and analyze samples.

For example, in Minnesota, retailers have computerized blending systems to ensure accurate blends of B2. However, in neighboring North Dakota, regulation is in the embryonic stages. "We have the statutory authority to draft rules to regulate biodiesel, and we are in the process of doing that right now," said Gary Berreth, state program manager for the North Dakota Underground Storage Tank Program. "To what degree we will actually go out and do that type of testing, I don't know. To be honest, I'm not completely sure our laboratory has the capability to do that."

Reddy happened upon the blending discrepancies while studying a biodiesel spill in a marine environment. "It is essential that the advertised blend be accurate for fairness to the consumer, performance of the vehicle, tax regulations, and emissions and carbon-cycling studies," he said.
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