What is AUS40? Your Guide to Marine Urea for IMO NOx Compliance

What is AUS40 and How Does it Work?

AUS40, also known as Aqueous Urea Solution 40%, is a high-purity fluid composed of 40% urea and 60% deionized water. It is specifically engineered for use in marine Selective Catalytic Reduction (SCR) systems to neutralize harmful Nitrogen Oxides (NOx) produced by ship engines.

The process is a simple chemical reaction:

1. Injection: The SCR system injects a precise amount of AUS40 into the hot exhaust gas stream.
2. Conversion: The heat converts the urea in AUS40 into ammonia (NH₃).
3. Neutralization: Within the SCR catalyst, the ammonia reacts with harmful NOx emissions.
4. Result: The reaction transforms the pollutants into harmless nitrogen (N₂) and water (H₂O), which are then safely released.

The Driving Force: IMO Tier III and NECA Regulations

The adoption of AUS40 is not just a choice—it's a necessity driven by international law. The primary driver is the IMO's MARPOL Annex VI, which sets strict limits on NOx emissions. Specifically, Tier III standards mandate an approximate 80% reduction in NOx emissions compared to Tier I levels. These stringent rules apply to ships operating within designated Nitrogen Emission Control Areas (NECAs), which include critical regions like the North American coast, the U.S. Caribbean, the North Sea, and the Baltic Sea.

Frequently Asked Questions (FAQ)