TORONTO, Ont. –Fleets and owner/operators will have a crucial decision to make in 2010, when engine manufacturers roll out two vastly different solutions to meet the EPA2010 emissions standards.
The next round of EPA regulations calls for a reduction in NOx (nitrogen oxides) to 0.2 g/bhp-hr. One way to achieve this is through an exhaust aftertreatment process called Selective Catalytic Reduction (SCR). SCR systems consist of a catalyst, a separate tank which houses urea -or diesel exhaust fluid (DEF) -and the associated plumbing. A small amount of DEF is introduced into the exhaust stream, causing a chemical reaction that breaks NOx down into harmless water and nitrogen.
This technology, which is already widely used in Europe, will be employed by Volvo, Mack, Detroit Diesel, Paccar and Cummins. However, Navistar (parent company of International Truck and Engine) does not like SCR for a variety of reasons, and has instead focused on becoming EPA2010- compliant by simply employing higher levels of Exhaust Gas Recirculation (EGR), the technology currently in use today. (Caterpillar announced this summer that it will no longer supply heavy-duty on-highway engines for the North American market in 2010).
Those with their feet firmly planted in the SCR camp call Navistar’s approach ‘massive EGR’. Navistar prefers ‘mature EGR.’
Tim Schick, director of marketing for International’s big bore engine business, says the company will increase the amount of exhaust gas recirculated through the engine by 10% compared to today’s engines. Contrary to reports, he insists EGR levels will be “way below 50%, even in the most extreme cases.”
He says advances in engine technology have allowed the company to become 2010-compliant without SCR by enhancing its EGR system and developing a high-pressure common rail fuel system that will boost pressures above 30,000 psi. The International MaxxForce’s durable compacted-graphite iron block will allow it to withstand the higher firing pressures, Schick says, adding the company will move to a five-stage injection cycle.
“We’re taking advantage of technology that just didn’t exist before,” explains Schick. “Our program is going very, very well and with time we have found more security with this path, rather than less.”
Navistar was originally joined on the EGR side of the fence by Cummins, but the industry’s market share leader dropped a bombshell on Aug. 13 when it announced it was switching paths in favour of SCR on its heavy-duty engine line. Cummins already was planning to adopt SCR on its midrange engines, which should make the mid-flight reversal easier to execute.
In a conference call with the trade press, Cummins said it decided to change course for two reasons: record fuel prices, which have made fuel economy a priority; and the emergence of a new catalyst material that Cummins says eliminates NOx more efficiently than traditional materials.
By using a copper-zeolite catalyst material, Cummins found it could improve fuel consumption by up to 5% compared to its EGR solution, Steve Charlton, vice-president of heavy-duty engineering with Cummins says.
Ed Pence, vice-president and general manager of Cummins heavy-duty engine business, adds “The business case for delivering industry-leading fuel economy performance from our products was too compelling for us to overlook, and therefore drove this decision.”
It should be noted, Cummins steadfastly denies that it encountered problems in developing its in-cylinder solution.
“That product was all set to launch in January, 2010,” said Charlton. “The program was performing well, the product was performing well and we were hitting all our targets.”(See pg. 55 for more).
Navistar seems unfazed by the Cummins announcement. Schick says International trucks will still be available with the Cummins ISX with SCR in 2010, so the development simply broadens the options for International truck customers.
Perhaps the biggest challenge facing Navistar is not meeting EPA2010 emissions standards, but fending off criticism from the SCR crowd, which continues to question the viability of an in-cylinder solution.
Randy Fleming, powertrain sales manager with Volvo Trucks Canada for one, has questioned whether an EGR solution will be able to achieve passive Diesel Particulate Filter (DPF) regenerations. He points out that NOx plays an important role in facilitating passive DPF regens. Actively regenerating the DPF consumes about 2.5 litres of diesel, he says.
Eliminating NOx in-cylinder means “near-zero passive re-generations,” Fleming said during a seminar at the Private Motor Truck Council’s annual conference in June. With SCR, on the other hand, engine manufacturers can produce as much NOx as necessary within the cylinder, take advantage of its chemical properties to conduct an efficient passive DPF regeneration and then eliminate the NOx downstream in the SCR catalyst. Navistar’s Schick insists International engines will continue to achieve passive regenerations.
“We don’t feel we’re going to have issues passively regenerating our engine for 2010,” he says. “When they say you need NOx to regenerate, what they’re really saying is you need heat. Yes, taken on the surface, less NOx out equals less heat out.”
However, Shick adds the new high-pressure common rail fuel system will produce less NOx than today’s engines in the first place and the regeneration process should not be impacted. Navistar also finds itself having to defend its use of ‘credits’ to become EPA2010-compliant.
“The folks not using SCR will not be meeting the EPA’s tailpipe emission levels,” says David Siler, director of marketing with Detroit Diesel. “They’ll be compliant, but not necessarily the cleanest. To meet the 0.2 g/bhp-hr NOx tailpipe limit, the only way to get there is with SCR.”
Engine manufacturers in the US have earned credits for surpassing previous emissions standards, and Navistar admits it will be cashing in some of those credits in 2010 to bring it into compliance. The company makes no apologies for doing so, since that’s why the system was put into place, says Schick.
“The inclination is there was a loophole somewhere, that it’s not a good thing and we found this loophole to produce dirty engines,” he counters. “We really have to back up and say that we hold, and the EPA holds, that this is a positive. They set up a program that rewards producing engines that are cleaner than they need to be at any given time. They very much promote achieving lower emissions early and they reward for that.”
For its part, SCR has not been immune to criticism itself. The widespread availability of urea has been voiced as a major concern, however engine manufacturers that will adopt SCR downplay the issue.
David McKenna, powertrain sales and marketing manager with Mack, points out that urea will be consumed at an approximately 3% urea-to-diesel ratio, so for every 100 gallons of diesel burned, a truck will require just three gallons of DEF.
“On a typical highway truck with a 13-gallon urea reservoir, at 6.5 mpg you’ll be able to run all the way from New York to Los Angeles and back to Denver, Colorado on 13 gallons of urea,” he says. The amount of urea required varies slightly by manufacturer. Cummins, for instance, touts a 2% urea-to- diesel ratio, which equates to about 6,000 miles between fill-ups based on a 20-gallon urea tank.
“We will optimize that ratio for the lowest cost of operation,” says Volvo’s Fleming. It’s expected DEF will be available at truck stops and truck dealers across North America, both in bulk and in portable containers similar to those containing windshield washer fluid. Currently, urea costs about three-quarters the price of diesel, Fleming notes, adding more than 100 million tonnes of the solution were produced worldwide last year.
As per EPA requirements, engines using SCR will be downgraded if the urea tank runs dry, meaning the driver will have to keep on top of monitori
ng tank levels and replacing the fluid when required. That driver interaction will be a deterrent for some fleets, Navistar hopes.
“All the emissions controls up until now have been passive, they don’t require direct driver involvement,” says Schick. “Now this one is active and (fleets are saying) ‘We’re not sure we want to go that route and add that extra complexity -this is going to provide an inconvenience we’d rather not have’.”
Schick also contends Navistar’s non-SCR approach appeals to body builders, who loathe the idea of losing frame rail space to SCR components. However, McKenna says the SCR system has been packaged “very efficiently.”
At the end of the day, manufacturers using SCR say fuel mileage will drive many customers to embrace the technology, especially when fuel savings of 3-5% are being promised.
Detroit Diesel’s Siler explains that without limiting engine-out NOx, manufacturers are able to better optimize their engines’ operating parameters.
“So essentially we’re getting better performance within the cylinder and also better performance in the particulate regeneration cycle,” he says. In testing, Siler claims Detroit Diesel’s DD15 with SCR is achieving about 3% better fuel mileage than its non-SCR equivalent.
“If you can move your truck from 6 mpg to 6.3 or 6.5 mpg, if you can put three, four, five cents per mile in your pocket at 100,000 miles per year, you’re not talking chump change,” adds Mack’s McKenna. “We’re seeing improvements of about 3-4%, including the cost of urea.”
Navistar doesn’t dispute the fuel-saving potential of SCR, however it does question the overall cost savings.
“We would recognize that there is the potential to re-tune the engines with SCR for greater fuel economy, we don’t dispute that,” Schick says. “But are the cost savings real? The fuel savings may be, but are the cost savings real? There, we do have an alternative view.”
He contends the cost savings achieved by burning less fuel may be offset by the cost of urea and the added complexity SCR presents.
The other knock against urea is its tendency to freeze at 12 F, which Schick says has not been lost on Canadian fleets, and those “in the northern tier” of the US.
Volvo’s Fleming says while urea does freeze, it won’t be an issue.
“Europe has an environment that’s every bit as cold as Canada. It’ll take no more time than now to get started,” he says. “The exhaust will immediately melt a few CCs, and the rest will be melted in the (heated) tank.”
So while the debate rages on, customers find themselves quickly approaching a major fork in the road. For the first time since the EPA began cracking down on heavy-duty diesel engine emissions, truck owners will have to choose between two radically different solutions.
The SCR camp remains confident escalating fuel prices will drive customers towards its more fuel-efficient solution.
“We explored all three of the known technologies at the beginning: NOx adsorbers; SCR; and massive EGR,”McKenna explains. “We decided to go with SCR for two reasons: number one, we can get down below the EPA2010 regulations with SCR relatively easily; and number two, we can improve fuel economy. With all that in mind, I really don’t see a down side to SCR, outside it’s one more thing for a driver to do. But if you have to replenish a very small SCR tank every second or third fill-up, and you can get 3-4% better fuel economy, what’s the question?”
Navistar, now the lone carrier of the non-SCR torch, counters that the complexity of SCR and the necessary driver involvement will make its EGR solution a winner.
“We view that we offer a very viable alternative to SCR, which we recognize is a valid technology. Our alternative is one of simplicity versus complexity and we feel there is no real operating cost disadvantage to that,” Schick surmises.