Metrology for a Biodiesel Future
ASTM International and the National Institute of Standards and Technology are teaming up to create standard reference materials for biodiesel that could give the world its first comprehensive measurement system for this promising alternative fuel.
The paradox of biodiesel is that its greatest advantage poses its most difficult technical challenge.
Biodiesel is a nontoxic, biodegradable diesel fuel produced from vegetable oils and animal fats. Most biodiesel contains so little sulfur that blending it with petroleum diesel helps fuel producers meet ultra-low sulfur diesel requirements. Engine manufacturers like biodiesel’s high lubricity and cetane (roughly analogous to gasoline octane) over petroleum diesel fuel. And biodiesel is a fully renewable resource that could make a sizable dent in the world’s reliance on petroleum and spur economic growth in developing nations that lack other fuel resources. Best of all, biodiesel can be produced from just about any biological material containing fat, from soybeans and sunflower seeds to algae and fish heads.
“That is the challenge,” says Robert Watters, Ph.D., chief of NIST’s Measurement Services Division. “When you think about pumping crude out of the earth and refining it, that is simple by comparison, very straightforward. Everything is pretty much from the same starting material. But with biodiesel, you have this incredible range of source materials.”
As a result, biodiesel fuels with different chemistries and performance characteristics could easily flood the market. That concerns everyone, from fuel producers and engine manufacturers to consumers and regulators. In response, standards development organizations around the world — chief among them ASTM International, the European Committee for Standardization (CEN), the German Institute for Standardization (DIN) and the British Standards Institution — have quickly developed standards for biodiesel. The resulting specifications and test methods have both striking similarities and important differences that need to be resolved.
Ellyn Beary, senior scientific advisor at NIST’s Chemical Science and Technology Laboratory, cites the iodine value in current European standards as an example. “The iodine value is used as an indication of stability, and an upper limit is specified in the European standards that is based on rapeseed oil,” she says. “However, if you make a biodiesel that works equally well in an engine but comes from another source, like soy, it won’t meet the specification.” United States, European Union and Brazilian technical experts are currently discussing this specification and others in an effort to move toward compatible specifications worldwide.
One Commodity, Many Sources
If biodiesel is to become a global commodity that can be produced from any feedstock and blended, traded and used with confidence anywhere in the world, then one of two things is needed: 1) a single, universally accepted biodiesel standard based on generic specifications, or 2) a harmonization of the standards used worldwide. Both options rely on technical consistency — laboratories everywhere being able to obtain near-identical results by conducting equivalent tests on virtually identical samples of a material. Such consistency relies on accurate and reliable metrology, and ASTM and NIST are working together and with the world’s standards community, to provide it.
Since the mid-1990s, biodiesel researchers and producers have helped lay the groundwork for an international biodiesel standard through their participation in ASTM International Committee D02 on Petroleum Products and Lubricants. This effort resulted first in a technical definition of biodiesel based on the chemistry of the fuel, then in ASTM D 6751, Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels. First issued in 2001 and continuously revised since, D 6751 establishes a specification for B100 biodiesel — 100 percent biodiesel that can be used by itself or combined with petroleum diesel to produce blends such as B10 (10 percent biodiesel, 90 percent petroleum), already in wide use.
D 6751 includes detailed requirements for everything from viscosity, flashpoint, cloud point and oxidation stability to percentages of water, glycerin and trace elements. The standard references more than 40 established test methods, specifications and guides for testing those specifications. Yet the metrology underlying D 6751 and other biodiesel standards in use around the world is metrology developed mostly for petroleum-based materials. And biodiesel is quite a different animal (and plant) altogether. Consequently, organizations everywhere are racing to be the first to develop a true biodiesel metrology.
The Race for Metrology
“There is a lot of international activity,” says Beary, “because the one who establishes a metrology that everyone uses or bases theirs on will have a competitive advantage.”
In 2006, ASTM International approached NIST to begin the development of biodiesel standard reference materials. NIST, a longtime Committee D02 participant, developed an SRM for ultra-low sulfur diesel. “In that technical environment, we had meetings and discussions with the people who are working on biodiesel,” says Bruce MacDonald, a physical scientist in NIST’s Measurement Services Division. Among those people was Steve Howell, technical director of the National Biodiesel Board, the national trade association representing the biodiesel industry in the U.S. “We invited him to talk to the scientists here at NIST, and in January 2007 he gave a presentation to 25 people representing five NIST divisions,” MacDonald says. This and other stakeholder input led CSTL to include biodiesel among its priority development projects for fiscal year 2007.
As in its work with other industries, NIST’s goal with biodiesel is to develop fundamental metrology rather than a suite of SRMs covering biodiesels from all sources. “What we want to do is to develop the critical minimum set of SRMs,” says Watters. For U.S. industry, that set is one SRM for soy-based biodiesel and one SRM for animal-fat based biodiesel.
The first step was to obtain representative samples of the two types of biodiesel. “The National Biodiesel Board has been providing [soy] biodiesel samples to manufacturers of engines and various organizations for a long time,” says MacDonald. “It’s a soy biodiesel product named ‘SoyGold,’ and there have been a lot of measurements done on it already. So we obtained samples of that.”
The animal fat-based B100 is the same material that ASTM uses in its Interlaboratory Crosscheck Program on biodiesel. Through ILCP, participating laboratories receive biodiesel samples. The laboratories conduct D 6751 analyses on the samples and return their test results to ASTM, which compiles a statistical summary of all results. By comparing their results with those of other laboratories worldwide, individual laboratories can assess the quality of their testing programs. And by using the same sample material as that for the first ILCP biodiesel test cycle, NIST gains a valuable set of measurements to supplement its own characterization efforts.
International competition to develop biofuel reference materials is intense, but the high stakes have also led to international cooperation. Through the Inter-American Metrology System (SIM), an agreement among national metrology organizations of the 34 Organization of American States member nations, the U.S. and Brazil have formed a partnership that makes the best use of the technical resources and experience of each and avoids unnecessary duplication of effort.
With its 30-year history of state-mandated ethanol use, Brazil possesses valuable technical and practical experience that can guide the U.S. in developing its own ethanol industry. For its part, the U.S. has world-class scientific and technical resources to help both countries conquer the challenges of biodiesel. As a result, NIST is working with Brazil’s national standards laboratory, Instituto Nacional de Metrologia, Normalização e Qualidade Industrial (INMETRO), to develop internationally acceptable certified reference materials for both anhydrous and hydrated ethanol and several biodiesel materials derived from a wide variety of sources.
A Measure of Confidence
“Everybody — D02, the petroleum producers, the National Biodiesel Board, auto manufacturers — wants biodiesel to be implemented in a way that is successful,” says MacDonald. It is largely about taking advantage of the potential benefits of biodiesel. Yet it is also about avoiding the potential pitfalls.
“Biodiesel presents the opportunity for climate mitigation, less dependence on foreign oil, being able to use a country’s own natural resources to make fuel — but what would happen if you introduced something that clogs your engine?” asks Beary. “Think of the economic implications and loss of credibility. So it has to be done right.” And for NIST, doing it right means giving the world the numbers it needs to have confidence in this fuel of the future.
Robert Ausura is a writer and photographer living in Gaithersburg, Md.