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Industry discussions have churned for months on whether heavy-duty truck manufacturers will use SCR (selective catalytic reduction) or EGR (exhaust gas recirculation) aftertreatment on 2010 engines. Most manufacturers say they will use SCR technology to meet EPA emission standards on their 2010 trucks. The lone hold out: Navistar International, which will use advanced EGR. The heated talks continued at NTEA’s Work Truck Show this past month in Chicago.
SCR advocates have their say
SCR requires diesel exhaust fluid and DEF tanks anywhere from 5 to 30 gallons to treat NOx. SCR systems will also include a doser, as well as the SCR catalyst, an aftertreatment control module and a DEF gauge. All SCR systems will incorporate emissions technology already on trucks, including DPFs and DOCs.
Questions remain on whether urea, a chemical additive in DEF composed of ammonia and carbon dioxide, will be readily available or pose a hassle for operators when it’s time to refill. Currently there are plans for more than 2,500 DEF dispensing locations in the United States, including major truck stop chains, engine distributors and truck dealerships.
DEF cost has also remained unclear, since it fluctuates just like other fuels. “Detroit Diesel buys it every day for well under $3 per gallon right now,” says David Siler, director of marketing, Detroit Diesel, “But obviously that could change by 2010.”
And the industry says it’s finding solutions on where to place SCR components. At NTEA, Freightliner’s mock-up of its M2 106 Business Class Model, (which comes standard with a Cummins engine) highlighted three SCR configurations parent company Daimler Trucks North America will use. One fits horizontally, while other options involve placing the system underneath the passenger side step or vertically stacking it, depending on space needs.
Steve Morelli, sales and marketing manager for Freightliner’s EPA 2010 team, says Detroit Diesel began testing its BlueTec technology in the United States in 2007. This SCR system has been used in Europe since 2005 and is now on more than 200,000 trucks.
In testing, Detroit Diesel addressed a primary concern about water-based DEF: the possibility it will freeze or evaporate at certain temperatures.
“We froze DEF tanks to see how long it would take to thaw [since DEF freezes at 12 degrees Fahrenheit], and determined both the tank and the DEF injection lines had to be heated,” Morelli says.
DEF does begin to evaporate around 90 degrees Fahrenheit, but Freightliner says DEF’s shelf life will not be compromised, as it can sit between six to 18 months without use.
Manufacturers are also addressing the SCR weight issue. On Freightliner trucks equipped with 2010 Detroit Diesel engines, for example, the typical vehicle weight will increase around 475 pounds.
“We’re working on a low-weight SCR solution, and are taking steps to ensure DEF doesn’t freeze,” says Stephen Ginter, vocational products marketing manager, Mack. “We used EGR in 2002 to reduce NOx, and we considered it for our 2010 solution. However, it doesn’t provide adequate fuel economy in our engine – our engine performs best by reducing EGR and instead using SCR along with a diesel particulate filter to reduce NOx.”
And in the EGR corner…
Navistar says its advanced EGR solution will include a high-pressure common rail fuel system to raise injection pressure and optimize combustion, while increasing the standard EGR rate by around 10 percent to reduce NOx. The company also contends its EGR solution will weigh less than competitors’ SCR aftertreatments. SCR advocates, however, voice concerns about EGR’s fuel economy and increased particulate matter, since the extra heat from EGR lowers NOx but raises PM levels.
Steve Guillaume, general manager, vocational trucks, Navistar International, says the company is addressing advanced EGR’s requirement for 10 to 15 percent additional cooling capacity and will use previously obtained EPA credits to meet 2010 emissions, which allow more time for Navistar to address these issues.
“The challenge isn’t getting to an 0.2 NOx reduction,” says Tim Shick, director, business and products strategy, Navistar International. “It’s realizing you need to do this and still bring fuel efficiency.
Navistar has remained committed to its EGR solution, claiming it will provide more uptime than SCR, since EGR-equipped trucks will not require DEF refueling or additional components typical of SCR.
What about cost?
With the exception of Volvo Trucks North America, which now says it will include a $9,600 surcharge on trucks equipped with its 2010 emissions solution, it’s unclear whether other manufacturers will post surcharges. Navistar’s Guillaume says to look for their pricing announcement this summer, which he says will be competitive with other manufacturers. Mack and Freightliner both declined to comment on their pricing.