STUTTGART, Germany — Selective catalytic reduction (SCR) technology will be the solution to the North American emissions challenge of 2010, says Andreas Renschler.

The head of DaimlerChrysler AG’s Commercial Vehicles Division, headquartered in Stuttgart, Germany, told Today’s Trucking it’s the only possible answer to the last round of U.S. Environmental Protection Agency (EPA) rules. Those emissions limits for 2010 are mirrored in Canada.

Renschler’s technical chief, Dr. Gerald Weber, agrees. “We believe it’s the only technology that’s mature enough to fulfill the [2010] emissions requirements,” Weber told Today’s Trucking in a recent interview at the DaimlerChrysler test track near Papenburg, Germany.

Other technologies are feasible in theory, he added, but could not be developed in time for commercial use in 2010. SCR would be installed on top of EGR and a particulate filter, Weber says.

Some 5000 Mercedes-Benz trucks equipped with SCR have already been delivered to customers in Europe, more than half of them at the toughest ‘Euro 5’ standard which isn’t required until 2009. The opposite of EGR, diesel engines equipped with SCR are actually 3-5 percent more fuel-efficient than those without it.

SCR was rejected by the EPA to meet 2007 emission regulations, as it was for the earlier round of standards in 2004, largely because it was feared that truck operators could not ensure that their vehicles would not be run without the liquid urea on which SCR depends. SCR trucks carry a small tank of urea, which is injected into a catalyst in the exhaust stream and then reacts to produce ammonia and to reduce noxious emissions. If the urea tank runs dry, the catalyst is rendered ineffective.

But Renschler has an answer for that objection — an empty urea tank would trigger engine de-rating and the truck would be hobbled, possibly left in limp-home mode so that the driver could at least get it to a service point.

While most enginemakers that currently rely on EGR have at least entertained the possibility of SCR as an emissions solution four years from now, Caterpillar, which is the only company that utilizes ACERT technology, warns against it for on-highway applications.

Cat cites the urea issue as its main reason for red flagging SCR as a North American solution. Also, Cat claims the use of SCR in mobile applications in Europe has shown that the cost benefits for SCR may not be as good as originally expected — that the combined cost for fuel and urea may negate nearly the cost benefits provided with SCR for customers.

But that’s not what the other engine folks are saying — especially those based across the pond. Volvo Trucks is the other company leading the charge for SCR adoption in the next round of emissions-cutting.

As for the potential urea obstacle, Volvo Powertrain vice-president of Engine Engineering Tony Greszler says that the need to have urea available at every fueling station might not be an issue by 2010. He predicts urea will be needed in such low concentrations by then — likely about 1 per cent of fuel consumed, down from current European rates of 4 per cent — that it would be very easy to tote around a few gallons of urea solution in jugs.