Plans are taking shape. Cummins Engine recently announced that it will use exhaust gas recirculation (EGR) and particulate matter (PM) filters to meet 2007 EPA exhaust emissions regulations. The company says its basic EGR design will be unchanged when the stricter standards are introduced, but it will add PM filters provided by its Fleetguard filtration and exhaust division.
EGR systems introduce a small amount of exhaust gas into the intake stream, cooling peak cylinder temperatures. This lowers oxides of nitrogen (NOx) emissions, but has traditionally raised PM levels, due to less efficient combustion. A PM filter, which resembles a muffler, extracts exhaust soot via a ceramic or metallic filter that’s continuously or periodically purged or regenerated.
According to John Wall, Cummins vice president and chief technical officer, the company’s decision was based largely on its confidence in the durability of its current design. The company says it has more than 30,000 EGR engines in service, with more than a billion miles, and has only had 23 failures – only one of which was related to EGR components. Cummins has backed the engines with its Uptime Guarantee program under which the company will provide rental trucks for up to three days if an ISM or ISX engine fails and can’t be repaired within 24 hours. The company recently extended that program for all engines placed in service through December 31, 2004.
Meanwhile, International Truck & Engine announced that it, too, will use EGR for 2007, along with PM filters, which the company has used successfully on its Green Diesel Technology products for the past three years.
It was initially thought that NOx adsorbers (aftertreatment) might be necessary for ’07, but, “we have demonstrated a breakthrough with our existing engine technology platform for 2004,” says Patrick Charbonneau, vice president, regulatory and technology affairs for International.
Both companies’ strategies rely on the use and widespread availability of ultra-low-sulfur (ULS) fuel, since fuel sulfur is responsible for a high percentage of PM in current engines and could plug or damage the PM filters planned for use in ’07. Federal regulations require that ULS fuel, in which sulfur has been reduced to fewer than 15 parts per million, must be available nationwide by mid-2006.
While Caterpillar has been quiet about its approach to ’07, I’d say it’s a safe bet that it will continue to use its ACERT system, along with some form of aftertreatment. Since the company has made it clear that it has made an enormous investment in that technology, I can’t see it going any other way.
An alternative to EGR with PM filters is selective catalytic reduction (SCR). SCR uses ammonia provided by introducing a urea/water mixture from a vehicle-mounted tank into the exhaust, upstream of a catalyst.
SCR reportedly can reduce NOx, while allowing for an engine calibration with better fuel economy. However, there are challenges, such as the need for additional vehicle tanks and an infrastructure for obtaining urea.
The fact that Volvo and Detroit Diesel recently held a Urea Distribution Stakeholder Group meeting to investigate ways to create a urea infrastructure has led some to believe that Volvo/Mack and Mercedes-Benz/Detroit Diesel might adopt SCR technology for ’07. But European sources tell me that while SCR’s drawbacks are easily justified in Europe, where fuel costs four to five times as much as in North America, it may not be palatable on this side of the pond as a solution in ’07.
Indeed, Mack and parent company Volvo announced in late January that they would use EGR/PM filters for ’07, citing fleets’ comfort level with EGR. There was no word from Detroit Diesel at press time.
While SCR looks like a no-go for ’07, as emissions requirements become even more stringent in 2010, SCR may make more sense, Cummins’ Wall says.