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What is SCR technology?

The SCR system, for Selective Catalytic Reduction, works with AdBlue®. It improves the environmental footprint of diesel vehicles. How does this complementarity work? What are the main advantages? What you need to know.

Understanding SCR technology

Combined with SCR technology, AdBlue® converts nitrogen oxides (NOx) emitted by the diesel engine into nitrogen and water vapour, non-polluting components already present in the atmosphere.


In practice:

1. AdBlue® is injected into the exhaust pipe upstream of the SCR catalyst.

2. Under the effect of heat, urea decomposes into ammonia.

3. By chemical reaction with ammonia in the SCR catalyst, nitrogen oxides from the engine are converted into nitrogen (a harmless gas, the main component of the air we breathe) and water vapour.


Most newer diesel vehicles that meet the Euro 6 standard are equipped with an SCR system powered by AdBlue®. The drivers of these vehicles will therefore have to top up AdBlue® regularly.


> Also read: Top up with AdBlue® in images


Good to know : On our website we offer you a simulator to find out if your vehicle needs AdBlue®. The simulator will also allow you to estimate your annual consumption of AdBlue®. Simply fill out the make, model, year of your vehicle and your mileage.

SCR technology and AdBlue®: a winning combination for air quality

AdBlue® combined with SCR technology makes it possible to reduce almost all NOx emissions without affecting vehicle performance.


This technology is not only intended for light vehicles, as it has been incorporated into heavy-duty vehicles since 2006. This is particularly interesting for this type of vehicle making long journeys.


> Also read: The Euros standards: what are they?

Towards a new SCR system?

At the end of 2019, the car manufacturer Volkswagen developed a new technology to reduce nitrogen oxide (NOx) emissions from diesel vehicles.


What’s special about this new system? Double injection of AdBlue® upstream of two SCR catalysts. One of the catalysts is located at engine level while the second is located at the underbody level of the vehicle, in order to optimise the treatment of nitrogen oxide emissions.


According to the manufacturer, based on real-world emission measurements, this new device has resulted in a reduction in nitrogen oxide emissions for the 2.0 TDI Evo engine compared to the previous generation. This device is destined to be deployed on a large scale.


> Also read: Focus on Volkswagen’s new double-dosing SCR technology for AdBlue®.