What is AdBlue and Why Your Diesel Fleet Needs It

SCR technology and emission reduction in diesel engines

In the transport and industrial machinery sector, environmental regulations have imposed an irreversible paradigm shift. With the arrival of the Euro 6 standard for heavy-duty vehicles and non-road mobile machinery, diesel engine manufacturers have had to integrate advanced exhaust gas aftertreatment systems. The heart of this technology is the SCR (Selective Catalytic Reduction) system, which mandatorily requires the use of a reducing agent commercially known as AdBlue.

For fleet maintenance managers in Madrid and throughout the peninsula, understanding the chemistry and operation of this fluid is vital to guarantee operational continuity and avoid costly failures in exhaust systems.

Chemical composition and ISO 22241 standard

Technically, AdBlue is not an additive mixed with fuel, but a liquid solution injected into the exhaust gas flow before reaching the catalyst. Its composition is strictly regulated under the ISO 22241 standard and is technically referred to as AUS32 (Aqueous Urea Solution 32%).

This solution consists of 32.5% high-purity urea and 67.5% demineralized water. This exact proportion is critical because it defines the freezing point of the mixture, which is located at -11 °C. Any deviation in concentration, whether due to incorrect dilution or evaporation, can cause urea crystallization in the injector or failure of the quality sensor, leading to engine power reduction (limp mode).

It is fundamental to acquire certified products that guarantee this purity. In our catalog, we have formats adapted to each logistical need, from starter kits to large volumes for intensive consumption:

• AdBlue Air1 3x10L: Ideal for occasional replenishment in small fleets or light machinery.
• AdBlue Air1 210L: Standard drum format for workshops and preventive maintenance.
• AdBlue Air1 1000L: IBC solution for large consumers and private service stations.

Operation of the SCR system and NOx reduction

The main objective of the system is the elimination of nitrogen oxides (NOx), highly polluting gases produced during diesel combustion at high temperatures. The chemical process occurs within the SCR catalyst:

1. AdBlue is injected into the exhaust pipe, where high temperatures (above 200 °C) cause its thermolysis, decomposing the urea into ammonia (NH3) and carbon dioxide.
2. The ammonia reacts with the NOx in the presence of the catalyst.
3. The final result is the emission of nitrogen (N2) and water vapor (H2O), components harmless to the atmosphere.

A modern Euro 6 engine can consume approximately between 1 and 3 liters of AdBlue every 100 liters of diesel, depending on the work load and the severity of the driving cycle. The system features level and quality sensors that constantly monitor the efficiency of the reduction.

Storage and product shelf life

AdBlue is a product sensitive to environmental conditions. Urea is hygroscopic and can degrade if exposed to extreme temperatures or direct sunlight for prolonged periods. The typical shelf life of the product is 12 months if stored at temperatures below 25 °C and protected from UV radiation.

For industrial fleets, we recommend rotating stock appropriately and verifying the expiration date printed on the packaging. Storage in stationary tanks should be carried out in covered areas or using tanks with thermal protection to prevent premature degradation of the AUS32 solution.