While sampling blended biodiesel fuels purchased from small-scale retailers, researchers at the Woods Hole Oceanographic Institution found that many of the blends do not contain the advertised amount of biofuel.

Marine chemist Chris Reddy and colleagues sampled pure biodiesel and blends from more than a dozen distributors across the United States. When testing fuels listed as 20 percent biodiesel (commonly known as B20), they found that the actual percentage of biofuel ranged from as little as 10 percent to as much as 74 percent. Only 10 percent of samples met the specifications for biofuel blends required for vehicles of the U.S. Department of Defense, one of the leading consumers of the products.


Pure biodiesel (B100) is a chemically prepared mixture of animal fats and vegetable oils, and it is often used in modified diesel engines. Biodiesel “blends” combine B100 with traditional petroleum-based fuels in a manner that allows them to be used in regular diesel engines. Retailers commonly sell blends that are 20 percent biodiesel (B20) or 5 percent (B5), while all diesel fuels sold in Minnesota are actually B2 (2 percent biofuel), in accordance with state standards.

Proponents of such fuels claim that they are more environmentally friendly because they emit less pollution—such as sulfur, particulates, and hydrocarbons—and may be less toxic for the environment when spilled.