Back of a truck with the Adblue logo

Why we need exhaust cleaning

Diesel engines are powerful and fuel-efficient, which is why they are widely used in trucks, buses, vans, farm machinery, and even some passenger cars. But when diesel fuel burns, it creates nitrogen oxides (NOx). These gases are harmful to people and the environment. 

To align with rigorous air-quality standards, modern diesel engines utilize Selective Catalytic Reduction (SCR) technology. This system relies entirely on AdBlue® to neutralize exhaust emissions. Because this process is vital for environmental compliance, your vehicle is designed to require a constant supply—without AdBlue, the SCR system cannot function, and engine performance may be restricted

What is Adblue?

AdBlue is a diesel exhaust fluid (DEF) used in vehicles with Selective Catalytic Reduction (SCR) technology to prevent harmful gases from being released into the atmosphere. AdBlue is a 32,5 % solution of high-purity, synthetically manufactured urea in de-mineralized water. It is a safe-to-use fluid. 

Yara's AdBlue product is certified according to ISO 22241 (ISO 22241-1, ISO 22241-2, ISO 22241-3). This international standard protects your vehicle from contamination which could cause serious damage. Using a urea solution of incorrect or low quality that does not follow these standards risks costly repairs.

  • A clear, non-toxic liquid.
  • Made of 32.5% urea (a compound also found in fertilizers) and 67.5% demineralized water.
  • Not a fuel and not mixed with diesel – it is stored in its own tank and injected into the exhaust system to remove the dangerous NOx emissions  

What is SCR?

Selective Catalytic Reduction (SCR) is an exhaust after-treatment technology. Its job is to transform dangerous NOx into water vapour and nitrogen. 

The catalyst is a ceramic or metallic unit coated with special materials that speed up chemical reactions. For SCR to work, it needs AdBlue as a reagent. 

Step-by-step: How AdBlue cleans exhaust

Visual diagram of how Adblue cleans an exhaust
  1. Diesel combustion – The engine produces exhaust that contains nitrogen oxides (NOx). 
  2. Injection – A small amount of AdBlue is sprayed into the hot exhaust gas stream.
  3. Decomposition – Heat breaks down AdBlue into ammonia (NH₃) and carbon dioxide (CO₂).
  4. Reaction in the SCR catalyst – Ammonia reacts with NOx over the catalyst surface.
  5. Clean exhaust – The reaction converts harmful NOx into nitrogen (N₂) and water vapour (H₂O) – both natural, harmless parts of the air we breathe. 

This process removes more than 95% of NOx emissions. 

If the AdBlue tank runs empty:

All vehicles will give plenty of early warnings before running empty. Should the tank not be refilled: 

  • The engine will either go into “limp mode” with reduced power or 
  • The vehicle will not restart until refilled. 

Why quality matters

SCR catalysts are sensitive. If AdBlue is contaminated, the catalyst can be permanently damaged. Repairs are very expensive. 

That is why only AdBlue that meets ISO 22241 standards should be used. Buying from trusted suppliers like Yara guarantees the correct purity. 

Frequently Asked Questions

AdBlue helps the SCR system turn harmful nitrogen oxides (NOx) into harmless nitrogen and water. 

No. AdBlue is stored in a separate tank and never mixed with diesel. It is injected only into the exhaust system.

Your vehicle will warn you in advance. If the tank is empty, the engine will lose power or refuse to start until refilled.

On average, about 5% of diesel consumption. For example, if a truck uses 100 litres of diesel, it will use around 5 litres of AdBlue.

No. AdBlue must meet the ISO 22241 standard. Homemade or poor-quality fluid can ruin the SCR system.