Most drivers don't have a clue about the percentage of free glycerin or Group I and II metals in the biodiesel they are pumping into their tanks. But if their vehicles sputter in the breakdown lane, questions about the quality and reliability of renewable fuel blends could idle a new industry before it gets started.
NREL Principal Engineer on Fuel Performance Robert McCormick says biodiesel quality is improving rapidly in the United States, with large producers consistently meeting specifications. However, some small producers still have trouble meeting national standards.
McCormick and Senior Engineer Teresa Alleman served as significant contributors to revised biofuels specifications recently published by ASTM International (formerly the American Society for Testing and Materials.) Research conducted by NREL provided the technical basis for setting the new standards. McCormick and other collaborators also have co-authored the 2008 edition of the Biodiesel Handling and Use Guide.
The rigorous ASTM process yielded stringent specifications to help ensure the availability of high quality biodiesel blends in the marketplace and bolster automaker support and consumer demand for biodiesel.
All Blends, All Feedstocks
The new standards are the result of years of research at NREL on how the properties of biodiesel blends affect engine performance, and apply to all finished biodiesel blends, regardless of the type of feedstock used to make the fuel.
The new standards will quickly play a crucial economic role. Diesel-powered trucking delivers 70 percent of the freight in the United States and represents 5 percent of the U.S. gross domestic product, so new fuel blends must prove reliable.
Several automakers are beginning to sell low-emission, high-mileage diesel cars and light trucks in the U.S., too.
"These standards will lead to an expansion of markets for biodiesel while at the same time ensuring that users have trouble-free performance," McCormick said.
Biodiesel is manufactured by the transesterification of domestic plant oils, animal fats, and recycled cooking oils. It's renewable and energy-efficient, and its expanded use displaces petroleum-based fuels. It's cleaner than conventional diesel, and can reduce levels of both air toxics and tailpipe emissions related to global warming.
The total U.S. production capacity for biodiesel reached million 2.24 million gallons in 2007.
"Today biodiesel could displace 5 percent on on-highway diesel use," McCormick said. "With aggressive feedstock development, displacing as much as 25 percent could be possible over the long-term."
ASTM Standards Protect Engines
Pure biodiesel is known as B100, but many engine parts are not compatible with the pure fuel. Burning B100 in an engine with incompatible parts can cause fuel system leaks, ruin a fuel pump, or clog a filter as the hose material gradually erodes.
At concentrations up to 20 percent, biodiesel blends can be used with minor or no modifications to the equipment. With the new specification in place, automakers and engine manufacturers can test B20 and know that consumers will be fueling their vehicles with a fuel of the same quality.
And those tougher specs are leading to improvements. Two years ago, half of the 32 biodiesel samples tested in McCormick's lab failed – what McCormick described as an "unacceptably large fraction" even for a new industry that still is experimenting with several different production and refinement methods.
In the most recent NREL tests with 56 producers, reported in 2008, samples representing nearly 90 percent of production volume met specifications and the major producers hardly ever failed the tests. See the NREL report Results of the 2007 B100 Quality Survey (PDF 522 KB). Download Adobe Reader.
While a few small and medium producers consistently produced a high quality product, generally the smaller producers continued to have significant failure rates. However, their combined production accounts for about 11percent of biodiesel production.
To learn more, visit NREL Biomass Research.