DaimlerChrysler’s plans to control emissions with SCR

HANOVER, Germany, — Not unlike conversations here these days, much of the talk — formally and otherwise — at the IAA Commercial Vehicles Show in Hannover, Germany, focused on coming emissions limits for diesel engines.

DaimlerChrysler, the continent’s biggest diesel engine producer for commercial trucks, says it will use an emission control system that uses selective catalytic reduction, or SCR, on all its trucks, buses, and coaches to meet Euro 4 emissions standards which come into force in October 2005.

Euro 4 is roughly equivalent to U.S. Environmental Protection Agency limits on nitrogen oxides (NOx) and other emissions scheduled to take effect in North America in 2007.

Significantly, DaimlerChrysler says it will use SCR on engines made by its Detroit Diesel subsidiary in North America.

SCR makes use of ammonia produced on board the vehicle from a solution of non-toxic, easy-to-handle aqueous urea. Urea (also called carbamide) is a colourless, odourless, crystallizing liquid readily soluble in water. A truck needs an extra tank for the urea, with an electronic metering unit for the reducing agent, and a ceramic catalytic converter that can be accommodated in the muffler. The urea solution is added to the converter to make the required ammonia.

The downside of using urea is that there is no simple way to distribute it to truck operators. Fuelling stations will need special pumps and separate holding tanks for it, so across Europe, work is being done to make the necessary changes now.

A key factor in all of this, according to DaimlerChrysler, is that European legislators will promote compliance with the Euro 4 exhaust limits by a cut in road tolls to reduce the burden of engine price hikes.

It’s also conceivable that trucks will be powered by Euro 5 engines even prior to 2008.