Biodiesel and Ethanol

How Does the 2010 EPA Standard Impact Fleet Biodiesel Use?

May 2010, Green Fleet Magazine - Feature

by Sean Lyden - Also by this author

Whether you already use a biodiesel blend in your fleet or are looking into it, you may have concerns about how this alternative fuel, produced from vegetable oils (such as soybeans) or animal fats and “blended” up to a certain percentage with regular diesel, will interact with the new 2010-emissions diesel engines.

Does biodiesel present unique challenges to the latest aftertreatment technologies developed for these engines? Does this alt-fuel negatively affect fuel economy? What do engine manufacturers say? Overall, does the EPA 2010 mandate really make a difference in biodiesel use, compared to the previous standard?

Work Truck magazine contacted representatives at the Engine Manufacturer’s Association (EMA), National Biodiesel Board (NBB), General Motors (GM), and Isuzu Commercial Trucks of America (ICTA) for their insights on the potential impact — short- and long-term — of running biodiesel in new 2010 diesel engines.

OEMs Limit Emissions with SCR TEchnology

The U.S. Environmental Protection Agency (EPA) requires all diesel engines manufactured on or after Jan. 1, 2010, to reduce nitrogen oxide (NOx) emissions by 83 percent from the 2007 standard — from 1.2g/bhp-hr (grams per brake horsepower hour) to 0.2g/bhp-hr.

To meet the new standard, most engine original equipment manufacturers (OEMs) — including GM, Cummins, Detroit Diesel, and ICTA, among others — have employed selective catalytic reduction (SCR) technology. SCR reduces NOx levels by injecting into a catalyst small amounts of urea-based solution called diesel exhaust fluid (DEF), which reacts with the NOx captured in the catalyst to convert the pollutant into harmless nitrogen and water before it’s emitted into the environment.

Why is eliminating NOx relevant to biodiesel use?

Do Biodiesel’s NOx Levels Impact Technologies?

According to an Environmental Protection Agency (EPA) fact sheet, “Clean Alternative Fuels: Biodiesel,” while biodiesel reduces particulate matter and hydrocarbon emissions, it increases nitrogen oxide emissions by 2 percent in B-20 (20-percent biodiesel, 80-percent regular diesel) and 9 percent in B-100 (100-percent biodiesel). An increase in NOx emissions is a concern because the gas contributes significant amounts of ozone to the environment.

If NOx emissions are higher with biodiesel, is the SCR system forced to work harder to break down the pollutants, thus leading to a shorter useful life of the aftertreatment system?

According to Roger Gault, EMA technical director, the difference in NOx levels in B-20 biodiesel blends compared to regular diesel is inconsequential — and so is the impact on the SCR.

“It’s a really small influence,” says Galt. “You’re probably real hard-pressed to identify biodiesel influence on the SCR demands. The SCR is doing so much already that to do a couple percent more is not enough to alter things very much.”

Gary Arvan, chief engineer for General Motor’s Duramax diesel engine, recently approved for biodiesel use up to B-20, agrees. “Higher NOx with biodiesel really is negligible. We just don’t see that effect [on the SCR] in running biodiesel,” says Arvan.

Rob Cadle, ICTA product planning manager, anticipates some impact on DEF depletion.

“Biodiesel wouldn’t necessarily affect the SCR system itself,” says Cadle, “but it may require a little bit higher urea consumption. So your DEF usage might go up, especially if you have more engine-out NOx.”

However, it’s precisely this notion that biodiesel creates higher engine-out NOx that Jennifer Weaver, OEM outreach and education specialist for the NBB, seeks to debunk altogether.

“The studies that generated the original higher NOx rumor were several years old and conducted on vehicles that were tested in a dyno lab, not in real-world applications,” Weaver points out. “And those tests revealed only minimal increased NOx levels when biodiesel blends were used.”

Weaver further explains, “More recent studies, also by the National Renewable Energy Laboratory [NREL] and other research entities, revealed that real-world applications actually show NOx neutrality or, even in some cases, a decreased NOx output with biodiesel blends. It depended very much on the duty-cycle of the engine and how it was being run. So biodiesel is not increasing the NOx output. The SCR systems completely take care of any NOx component in the exhaust. You’re not being penalized in any way by using biodiesel.”

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