SCR (Selective Catalytic Reduction)-based BlueTec is also the emissions platform for a set of clean diesel cars and SUVs Mercedes and Chrysler group has announced will enter the US market starting later this year. (Earlier post).

The 10,000^th truck went to freight company GRT Wittwer Transport which operates a fleet of some 90 trucks.

The BlueTec systems reduce emissions of pollutants such as oxides of nitrogen and particulates by up to 80% from currently permissible levels.

The operating principle of SCR is that unwanted nitrogen oxides are converted into harmless nitrogen and water vapour by the addition of ammonia as a reducing agent in a catalytic converter.

A non-toxic and odorless, aqueous urea solution known as AdBlue—which is held in a separate on-board tank—is used for this purpose. Under the control of the engine management system, AdBlue is sprayed into the hot exhaust gases as required.

DaimlerChrysler combines the SCR technology with improved engine design optimizing combustion that reduces the engine-out emissions of particulate matter. The efficiency of the combustion process means that the engine-out emissions of particulate matter and fine particles are already so low as to make a particulate filter redundant, according to DaimlerChrysler.

Independent tests (for example by the TÜV-Nord technical inspection authority) have demonstrated the effectiveness of BlueTec in reducing fine particle emissions.

The optimized engine control also slightly improves fuel efficiency. DaimlerChrysler engineers have measured an advantage for new BlueTec diesels of up to 5% versus Mercedes-Benz trucks equipped with Euro-3 technology.

DaimlerChrysler decided a number of years ago to use SCR technology to meet Euro-4 and expected Euro-5 standards and as a basis for meeting future even more stringent European emissions standards.

All other European manufacturers have followed suit and are developing Euro 5 technologies based on SCR. Interim solutions based on a combination of existing technology and additional components are only being offered for Euro 4, which will become mandatory in the autumn of this year.

Mercedes-Benz began introducing its Euro-5 capable BlueTec commercial trucks in the European market in February 2005, starting with the Actros heavy-duty trucks. BlueTec is now in the Axor and Atego truck ranges as well.

There are now around 1,500 public-access AdBlue refuelling sites in Europe, ranging from the Arctic Circle to southern Spain and from Ireland to Moscow, Russia.