It wasn't just biodiesel that had a big year in 2006. Virtually every diesel-related industry underwent 12 defining months. Companies whose emissions control devices were being finalized made last-minute design changes before commercial integration with 2007 models, which must meet decidedly lower emissions thresholds. These exhaust-treatment components-sensitive to sulfur-have been under development for years, building extended anticipation of diesel fuel's 33-fold reduction in sulfur. Because of all the unknowns still present in people's minds onlookers might get the impression that these stringent U.S. EPA regulations were dropped on the diesel industry without warning. That wasn't the case. Questions lingered, however, as Chris Sharp of the Southwest Research Institute expressed at the 2006 National Biodiesel Conference in San Diego. "I think we'll find out a few things the way we'd rather not," he says. Diesel experts at the gathering also expressed concerns about uncertainties with new diesel technologies and ultra-low sulfur diesel (ULSD), which are commanding appreciable resources already-without consideration of biodiesel. "It will be much worse if the biodiesel is out of spec," Sharp indicated.

Ultimately, this year was a period of time when problems of a recent past and concerns of a not-so-distant future converged. That result was an intense focus on biodiesel fuel quality. Damage control from experiences in Minnesota and other locales in recent memory, where off-spec biodiesel had been deemed partially responsible for plugging filters, motivated some of the emphatic focus on quality. Fear of condemnation by truck and bus manufacturers, fuel blenders, distributors, retailers and-perhaps most importantly-those who truly believe in the benefits of bodiesel use, have also compelled industry leaders to hammer home the message that quality is paramount. Moreover, the potentially traceable chain of supply may lead to monetary damages for those fuel makers found liable for off-spec product. As Leland Tong, chairman of the National Biodiesel Board (NBB) Accreditation Commission, and Paul Nazzaro, NBB petroleum liason, wrote in their October contribution piece to Biodiesel Magazine, "With explosive growth comes the challenge of maintaining fuel quality from the producer to the end user. Biodiesel stakeholders realize the importance of fuel quality and are becoming more involved in petroleum outreach. It is important to recognize that each link in the supply chain is critical. Producers and marketers must keep biodiesel and biodiesel blends on specification all the way through to the consumer." Changes to ASTM D 6751 were made to demonstrate this conviction to some degree.

It's Not Your Granddaddy's (Bio) Diesel
Significant changes to diesel systems have occurred in the past several years. Today's diesel systems aren't the compression ignition engines of Rudolf Diesel's time. The "new" diesels are high-tech machines calibrated for cleaner, more efficient operations-and they are increasingly sensitive to changes in fuel. Therefore, biodiesel must meet the highest evolving standards of quality.

D 6751 was modified this year to lower acceptable limits on calcium and magnesium, which, like sulfur, can affect the proper functioning of diesel particulate filters and NOx abatement equipment. "The biodiesel industry is committed to working with engine makers and exhaust aftertreatment companies to do what it takes to boost automakers' support of biodiesel blends with new diesel technology," Steve Howell says. Howell is NBB technical director and also chairs the ASTM task force on biodiesel standards. "That means ensuring that high-quality fuel specifications exist, which recognize and adapt to important changes in diesel technology," he says. According to Robert McCormick, principal engineer with the National Renewable Energy Laboratory (NREL) in Golden, Colo., new sodium and potassium levels were also introduced this year, limiting both to five parts per million.

These changes to D 6751 affect B100 only. According to the NBB, however, modifications made to the standard were needed to advance the development of a new B20 spec. A stand-alone quality spec for B20 will be required if industry proponents expect sweeping B20-acceptance by the major diesel-vehicle makers. Biodiesel blends up to B5 are supported by many of the major original equipment manufacturers, but that's not the case with B20, yet.

According to Howard Fang, technical advisor with Cummins Materials Engineering Group, who works primarily with fuel, lubes and aftertreatment devices, a ULSD-based B20 shows a disconcerting phenomenon in the lab. Using the ASTM D 2274 method to evaluate fuel deposits, a fixed amount of fuel gets heated to 95 degrees Celsius for 16 hours with a constant flow of oxygen. After heating, the deposits are collected through filtration, and then the deposited amount is weighed. "I think the limit for ULSD is one or two milligrams per 100 milliliters," Fang told Biodiesel Magazine. "When we mix with B20 biodiesel, the deposits show a tremendously large value in that B20 or B30 area." He calls this B20's antagonism effect of deposit formation. "When we run the [borderline spec] B100, for example, it generates 10 milligrams per 100 milliliters based on the D 2274 test," Fang says. "ULSD should be low, like 1 milligram per 100 milliliters. Theoretically there should be a straight line between them if you plot these deposits on a Y axis, and on the X axis is the biodiesel blends." That's not the case, and work will continue into 2007 to solve this problem.

Future changes to the quality standard may include the first-ever oxidation stability standard. McCormick says he believes oxidation stability and oxidative degradation, which pertain to the stability of the fuel, need to be monitored. "If a B100 is of high quality-well below the acid number standard and meeting all other standards easily-it might still go out of spec for acid during storage pretty quickly if it is unstable," he says, adding that reasonably stable B100 with an acid value that's not pushing the limit is less likely to degrade during storage. Others indicate that D 6751's 0.24 percent limit on total glycerin free and bound needs to be adjusted. Remnant free glycerin in the finished B100 fuel is rarely a problem, but bound glycerin in the form of mono- and di-glycerides-the direct result of incomplete transesterification-is problematic. Concerns from some industry experts about lowering the total glycerin limit exist, however. Gary Knothe, USDA Agricultural Research Service scientist and renowned expert on biodiesel properties, says reducing trace contaminants resident in biodiesel could adversely affect lubricity, something that's lacking in ULSD.

While ASTM specifications tell producers what criteria need to be met for quality fuel, it doesn't tell producers or distributors what steps to take that better ensure getting there. BQ-9000, the only quality assurance program tailored for the biodiesel industry thus far, has been heavily promoted this year as a way to help make certain that quality standards are met. "Granted, [implementing BQ-9000] doesn't come without cost or some effort, but keeping off-spec biodiesel from entering the marketplace is critical to building consumer confidence in biodiesel," Tong and Nazzaro wrote. "The stakes are too high to ignore these steps." The two go on to say that distributors should "trust but verify" certification by sampling. "Testing samples for total and free glycerin, acid number, flash point, and water and sediment serve as a good check to help ensure that the product entering the system is meeting ASTM D 6751 specification," they wrote.

Enhancing the Burn
For years, biodiesel has been blamed for slightly increasing NOx output from diesels. However, recent work by various organizations-the U.S. DOE, NREL, Texas A&M University, the North Carolina Department of Transportation and the U.S. Navy-show biodiesel blends like B20 are essentially "NOx neutral." This information defies results from the antiquated data that the EPA produced by using engine dynamometer tests. Jake Stewart, co-founder of the Biodiesel Coalition of Texas, tells Biodiesel Magazine that the EPA's historical emissions data on biodiesel relied too heavily on an unrepresentative number of diesel engines, hence producing defective data on biodiesel emissions. Also, engine dynamometer test results may not accurately portray the real-world operations of diesel vehicles such as transit or school buses, and other applications. Chassis dynamometer testing, however, may capture a more representative look at emissions profiles from such applications.

With questions mounting in 2006 regarding fuel effects on diesel systems as commercial production of clean diesels drew closer all year, conjecture on biodiesel's ill effects on such advanced emissions control systems were thrown out the window. Diesels produced for model year 2007 will require diesel particulate filters (DPFs), which trap soot while allowing gases to pass through a permeable cell-wall structure. As more soot collects, however, a back-pressure builds in the exhaust. Therefore, a critical aspect to the proper functioning of these devices is the occasional burn-off, or regeneration, of this trapped soot in order to keep back-pressure to a minimum.

Compared to gasoline engine exhaust, diesel exhaust is cool. This low-temperature characteristic of diesel exhaust necessitates intervention on some level to either boost exhaust temps and initiate regeneration, or to lower the temperature at which the soot can be incinerated. This can be accomplished many different ways: by the addition of a fuel-born catalyst, catalyzing the DPF with imbedded precious metals, and the addition of a diesel oxidation catalyst upstream of a noncatalyzed DPF, to name a few. Tests conducted and/or released this year by NREL, Penn State University, and Cummins, among others, all demonstrate that biodiesel and even low blends like B5 can significantly lower the temperature at which particulate matter burns. However, if biodiesel doesn't meet quality standards, the benefits the fuel can offer clean-diesel technology may be outweighed by costs incurred by the use of off-spec product-one more reason to focus on producing a superior fuel.

Ron Kotrba is a Biodiesel Magazine staff writer. Reach him at rkotrba@bbibiofuels.com or (701) 746-8385.