Cars to use SCR Engine Technology requiring AdBlue – Renault Truck Boss


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In order to meet stringent Euro 5 engine emission legislations, certain car and light commercial engine manufacturers will be required to use SCR (Selective Catalytic Reduction) technology.  That’s according to Stefano Chmielewski, CEO Renault Trucks in a conversation with the Press at the end of the Cape to Cape Adventure at the Cape of Good Hope in South Africa.  This will require the use of AdBlue – a liquid urea additive – to aid the emission control system.  A number of truck manufacturers have developed this technology for the Euro 4 regulation primarily to ensure that engine temperatures do not get overheated while maintaining fuel efficiency.  Mr. Chmielewski cites that car and van manufacturers will have to overcome a similar problem in this way.  “I can say to you that the next generation Renault Kangoo will be using SCR and AdBlue.”


The Euro 5 proposal 


In December 2005 the European Commission released the so-called Euro 5 proposal[1], a regulation laying down common standards and limit values for emissions of pollutants – nitrogen oxides (NOx) and particulate matters (PMs) in particular – from new passenger cars and light commercial vehicles.


In its proposal for the Euro 5 regulation, the Commission states that ”…the Commission wished to avoid an obligation for installing an additional NOx after-treatment system at this stage. As the technology for further NOx reduction is not yet mature, it is therefore proposed not to reduce NOx emissions beyond the 200 mg/km limit value”. 

DeNOx technologies 

There are mainly two technologies that efficiently reduce emissions of nitrogen oxides (NOx) from diesel engines: i) NOx Adsorbers (also called NOx traps) and ii) selective catalytic reduction technology (SCR) with aqueous urea. NOx Adsorbers store the nitrogen oxides chemically in a NOx trap before reducing them intermittently by running the engine in rich mode. The SCR technology uses a catalytic converter, which, by injecting aqueous urea into the exhaust system, converts the nitrogen oxides into nitrogen and water, both harmless to the environment and human health.

 The SCR is in most cases the preferred technology, as it has the potential to achieve 90+% NOx reductions with no increase in the fuel consumption. Indeed, in addition to reducing NOx emissions, experience with SCR in heavy duty vehicles shows fuel savings of between 5 and 7%[2]. It is assumed that substantial fuel savings can also be achieved in light duty vehicles and passenger cars. Lower fuel consumption not only makes it cheaper for the consumer, but it also ensures lower CO2-emissions, all at the same time as the emissions of NOx are reduced.

 In contrast to what the Commission proposal states, the SCR technology is a mature technology that efficiently reduces emissions of NOx from diesel cars. The technology is already widely in use in heavy duty trucks across Europe. In addition, passenger cars and light duty vehicles with SCR technology, from major brands like Mercedes Benz, are to be launched shortly on the US market due to stricter NOx regulations in the US.

 DeNOx protects both health and the environment 

Road transport is a large net contributor to air pollution and the introduction of deNOx technologies allows for EU countries to comply with the requirements of the Gothenburg Protocol and the objectives under the Clean Air for Europe (CAFE) Programme. In addition to being hazardous to the environment, NOx is a threat to human health, contributing to significant social costs. A recent study from the Commission estimates that the average cost of damages in EU25 of NOx emission may amount to 12,000 euro/tonne[3].

Available technology on the market – exported to the US

US legislation requires NOx limit values to be below 87 mg/km in all 50 states as of 2007, and several car manufacturers, including European ones, are already announcing the launch of passenger cars with after-treatment systems for deNOx.

 In January of 2006 Mercedes-Benz/DaimlerChrysler unveiled two new diesel cars complying with the new US standards, the E 320 BLUETEC and the Vision GL 320 BLUETEC, both utilizing SCR technology. The E 320 will be launched for sales nationwide in the US in the autumn of 2006[4]. DaimlerChrysler will offer passenger cars with SCR technology in the European market [5].

 Global harmonization?

 US limit values for NOx are set to 87 mg/km as of 2007. In Japan, new regulation – scheduled to go into effect in 2009 – will require NOx values from diesel cars not to exceed 80 mg/km. As EU legislation stands today, clean diesel cars with after-treatment systems will not be required in the EU until 2014. At the same time, European car companies will soon be exporting cars with deNOx after-treatment technology to the US. As a region that has already experienced the benefits of regulatory harmonization, it is surprising that the EU does not opt for setting similar standards to those of its major trading partners – especially in the field of environmental and human health protection, where the EU is normally known for being the pioneer.

 What is technically feasible in Europe?

The SCR technology is well established. Introducing deNOx after-treatment across the board in the EU is a challenge due to the large number of diesel cars and models in Europe. However, the relevant technology is at hand and a delay of introduction till 2014 (current proposal if Euro 6 is included as a second step in Euro 5) is difficult to justify in light of what is happening in the US and Japan. It is important to remember that almost half the diesel passenger vehicles certified for Euro 4 already meet the proposed Euro 5 NOx limit values. Indeed, the best performing diesel vehicles currently in the market have NOx emissions below 150 mg/km without after-treatment[6]



[1] The full name of the regulation is “Proposal for a Regulation of the European Parliament and of the Council on type approval of motor vehicles with respect to emissions and on access to vehicle repair information, amending Directive 72/306/EEC and Directive ../../EC”

[2] “Emission Control Technologies and the Euro 5/6 Emission Legislation”, AECC,

[3] “Damages per tonne emission of PM2.5, NH3, SO2, NOx and VOCs from each EU25 Member State (excluding Cyprus) and surrounding seas,” March 2005, AEA Technology Environment,

[5] Emission Control Technologies and the Euro 5/6 Emission Legislation”, AECC,

[6] International Council on Clean Transportation,