BLUETEC in commercial vehicles
Different approaches in Europe and the U.S.
It’s been less than two years since they were launched on the market, but already more than 100,000 Daimler Trucks commercial vehicles equipped with BLUETEC have been sold around the world. Most of these already meet the EURO 5 emission standard, which won’t go into effect until 2009. Orders are also on the books for a further 20,000 BLUETEC commercial vehicles from the Actros, Axor, Atego, Econic, and Unimog model series. “Our Mercedes-Benz BLUETEC trucks make us both a pioneer and the most successful supplier of this innovative diesel technology,” says Andreas Renschler, head of Daimler Trucks Division, which along with Mercedes-Benz trucks includes the three U.S. brands Freightliner, Sterling, and Western Star, and the Japanese Fuso brand.
The division’s Mercedes-Benz and Setra bus models are also available with BLUETEC 4 or BLUETEC 5 engines. The BLUETEC 5 units are in some cases available as EEV (Enhanced Environmentally Friendly Vehicle) variants, whose additional particulate filter enables them to meet the EEV limits, which are even more stringent than EURO 5. Unlike EURO 5, the EEV standard in the EU is not legally binding. Instead, it’s a label that allows manufacturers to certify that their Euro 5 vehicles have very low emissions.
The technical foundation for all clean BLUETEC vehicles in Europe is an extremely effective system for reducing nitrogen oxides in exhaust gas through the use of SCR technology and the AdBlue additive. The engineers who develop engines for Daimler Trucks’ three U.S. brands had to take an alternative approach to meet the EPA 07 emission standard that has been in effect in the country since January 2007. EPA 07 has limits very similar to those stipulated by EURO 5. The reason for the different approach has to do with the fact that a nationwide supply infrastructure for AdBlue could not be established across the vast area of the U.S. in time for the introduction of EPA 07.
However, the U.S. government did ensure at an earlier stage than the EU that only low-sulfur diesel would be sold at filling stations in the country. That’s why an alternative strategy for achieving compliance with EPA 07 was developed, one that involved intensive exhaust gas recirculation to reduce nitrogen oxide emissions. This measure invariably leads to an increase in diesel particulate emissions, however, and this necessitated the use of a closed particulate filter. As it turns out, the heavy-duty truck manufacturers on the North American market weren’t the only ones to choose this option, as several Daimler competitors are now offering heavy-duty trucks that use exhaust gas recirculation rather than SCR technology in Europe as well.
Markus Kemmner, who is responsible for Exhaust Treatment at Mercedes-Benz Commercial Vehicle Development, explains why Daimler Trucks decided to utilize different solutions for the two markets: “The lack of a comprehensive AdBlue infrastructure in the U.S. forced us to adopt a different approach there — but according to our studies, the most economical denoxification solution by far is SCR technology in combination with AdBlue.” That’s certainly no secret to European customers operating BLUETEC commercial vehicles, who report fuel savings of between two and six percent.
The situation is exactly the opposite with the alternative strategy, since it cannot be implemented without increasing fuel consumption. Kemmner therefore has his doubts as to whether the upcoming new emission limits in Europe and the U.S. can be met without SCR denoxification — and he believes that even if they can, the result will be higher costs. He also thinks the particulate filter system’s sensitivity to sulfur will be a problem as long as low-sulfur diesel remains unavailable on a broad scale in countries bordering the EU.
