Daimler prods U.S. EPA, competitors for Urea-SCR on light-duty diesels for Tier 2 compliance

Diesel Fuel News, Oct 27, 2003 by Jack Peckham

Washington, DC -- At an Alliance of Automobile Manufacturers-sponsored diesel car "ride and drive" event here, DaimlerChrysler (DCX) revealed to us that it's lobbying U.S. EPA and competitors to support urea-selective catalytic reduction (SCR) for upcoming EPA Tier 2 light-duty vehicle emissions compliance.

DCX meantime is among those leading the effort to put together a urea-SCR infrastructure for heavy-duty EPA 2007-compliant diesel trucks, too (see Diesel Fuel News 8/18/03, p1; 6/23/03, p1).

As DCX passenger car certification and regulatory affairs director Rudolf Thorn explained to us here, commercial success for the U.S. diesel car market means getting inside EPA Tier 2/Bin 5 limits, in order to avoid costly offsetting sales of higher-bin diesels with lower-bin gasoline cars.

Problem: In order to ensure full compliance on all EPA test cycles and the 120,000/150,000 miles durability requirements, "you'd need a NOx trap with a displacement six to ten times the engine displacement and that's impossible" to fit on a car, he said.

Regulators pushing extremely low limits on NOx, particulate matter (PM) and carbon dioxide (CO2) simultaneously, while blocking urea-SCR, would "kill the diesel," he said. Diesel particulate filters (DPFs) could add (Euro)$500 to car costs, while a NOx trap could add another (Euro)$500-700, plus impose a 3-5% fuel penalty that would put-off customers, he said.

While a handful of automakers have demonstrated partial Bin 5 compliance with DPF/NOx trap combos at EPA test labs in Ann Arbor, Mich., none have come anywhere near 150,000 miles durability, he pointed out.

Problem: NOx traps age over time and performance degrades, making Bin 5 compliance dubious. "We've been developing a NOx trap for five years now and it's only 55% efficient with an aged catalyst," he said.

"That only gets you to Bin 8. So, we won't have a 2007 model diesel" for the U.S. unless an alternative can be found.

"Nobody has passed SFTP requirements with a NOx trap; it's only possible with a urea-SCR system," Thom told us. "But that's only possible when we automakers have a common position [in discussions with EPA].

"If the U.S. wants to reduce fuel consumption and avoid oil imports, [then] we could introduce diesels with 20-40% better fuel economy. Or we could support a hybrid strategy like that of Toyota, but that only gets better economy on city-drive cycle and nothing on the highway."

Besides buttonholing officials from several other major automakers here, Thom also said he was meeting with EPA mobile sources director Margo Oge to urge her to consider the advantages of urea-SCR. DCX and some allies (including Volvo/Mack) are trying to find ways to resolve EPA's worries about urea infrastructure and assurance of motorist urea tank refilling.

"We have to make things that are possible and payable," he said, which is why automakers and engine makers in Europe have already come to a common agreement on urea-SCR, initially for heavy-duty but eventually light-duty, too.

DCX earlier showed it could hit EPA Bin 3 with a diesel car and light truck equipped with exhaust gas recirculation (EGR), urea-SCR and a diesel particulate filter (DPF), as explained at the recent Diesel Engine Emissions Reduction (DEER) conference (see Diesel Fuel News 9/2/03, p14).

Another DCX official explained to us here that a typical diesel car would only need about $10 worth of urea each year--not a financial issue, although urea availability and refilling convenience remain an issue.

In subsequent discussions with other officials here, one DCX representative told us that International Truck & Engine might change its current position favoring NOx traps over SCR.

Reason: During a recent "urea distribution stakeholder group" meeting of engine makers, urea suppliers, truckstops, refiners, fleets and truck makers, International was a surprise attendee, this DCX official said. Rationale: International's vehicle engineers are discovering heat-rejection packaging problems with alternative NOx-control schemes, while International's engine engineers aren't seeing such problems, this official suggested.

However, International spokesman Roy Wiley later told us that such a suggestion of a change-in-attitude toward SCR is just "rumor and speculation. The bulk of our engine business is medium-duty diesels and you can't expect every diesel fuel station to offer urea." Hence International's presence at the stakeholder meeting was "probably as an observer" rather than advocate, Wiley said.

However, another DCX official said that "once urea infrastructure starts to become real, that's when the dissenters will think about coming over" to SCR.

Automatic engine shut-down scheme isn't the right way to ensure drivers refuel with urea, but an automated engine management warning display (more attention-grabbing than a malfunction indicator light or "MIL") alerting drivers to impending urea run-out probably could work, this official suggested.

* Ford Sees Lack of 'Momentum'

Meantime, Ford--developer of a novel urea/diesel co-fueling nozzle scheme (see Diesel Fuel News 9/29/03, p13)--still perceives a lack of "momentum" that would be required to convince EPA to allow SCR.