Frequently Asked Questions (FAQ)

What is the Marine Urea Solution solution?

Marine Urea Solution, also known as AUS40, is a 40% urea-based solution used for the purpose of reducing Nitrogen Oxides (NOx) emission from vessels’ exhaust pipes.

What’s the shelf life of the Marine Urea Solution?

The shelf life of the 40% Marine Urea solution is around 18 months when stored at between 0 to 25°C (or in Fahrenheit, 32 to 77°F). Below is the estimated shelf life of the Marine Urea Solution based on average storage temperature.

Average Storage Temperature (°C)Average Storage Temperature (°F)Shelf Life (At least)
0-2532 – 7718 months
Less than 30Less than 8612 months
Less than 35Less than 956 months
More than 35More than 95Best to check every batch before use. Marine Urea Solution is unstable at such high temperatures.

Why is it essential to use the Marine Urea solution to control NOx emissions?

It’s important to reduce Nitrogen Oxides (NOx) emissions from the marine vessel’s exhausts as the gas is known to cause lung cancer.

How can a Marine Urea solution reduce your marine engine’s NOx emissions?

As the Marine Urea Solution is sprayed into the flue gas and steam, the hot exhaust breaks the solution into various components. The ammonia, the active component within the Marie Urea Solution, proceeds to react with the NOx to form harmless nitrogen and water molecules instead.

Will the 40% Marine Urea Solution freeze if the vessel always sails in freezing temperatures?

The freezing point of the 40% Marine Urea Solution is around 0 degrees Celsius (°C). This may only become a problem when the vessel is always sailing in regions with sub-zero temperatures.

Not to worry, vessel designers have thought this through. The Marine Urea storage tank is usually placed close to the hot engine room. Alternatively, the tank can be placed close to the hull. The ocean is rarely below 0 degrees Celsius (°C), so the Marine Urea Solution is unlikely to freeze.

To vessel designers, do take note of the shelf life and storage temperature (link to another article for shelf life) for 40% Marine Urea Solution. If you need more information, feel free to contact us.

Can the vessel choose not to use any Selective Catalytic Reduction (SCR) system to control the marine vessel emission?

Unless your vessel fulfils the conditions set by MARPOL, the answer is no. View MARPOL Regulations.

Why is the Marine Urea Solution used for SCR and why is it exactly 40%?

The Marine Urea Solution is chosen due to its non-hazardous component (this largely depends on the country’s jurisdiction). As such, the solution is relatively safer to handle compared to other alternatives. 

40% is chosen by most marine Selective Catalytic Reduction (SCR) system makers as it is the most efficient ratio. For the same volume of Marine Urea Solution, 40% will be able to treat more exhaust compared to 30%, which means that the same amount of volume will last you longer.

What’s the alternative to Marine Urea Solution (AUS40)?

Ammonia solution is the alternative. However, it is highly corrosive and very dangerous to handle. In most countries, special licences and permits are required to transport, supply and handle ammonia. This is why Marine Urea Solution (AUS40) has become the preferred and safer choice to control NOx emission.

Why is good quality Marine Urea Solution (AUS40) important?

In a marine Selective Catalytic Reduction (SCR) system, one of the many expensive components is the catalyst. When bad quality Marine Urea Solution (AUS40) is introduced into the SCR System, the impurities contained in the solution will clog up the SCR catalyst and render its effectiveness and eventually (and rapidly) to complete uselessness. 

The following consequences may happen:

  • The Marine SCR catalyst will need to be changed before it is due.
  • The clogged Marine SCR catalyst may cause problems for the other components.
  • At the next port call, the vessel would fail the NOx emission test and be subject to penalties or delays (depending on the marine/port authorities).

Therefore, it is important to pick reliable Marine Urea Solution (AUS40) suppliers.

Urea Handling

How should urea be stored onboard a ship?

Urea should be stored inside a tank within the vessel. The tank will be made of compliant materials or coating stipulated by ISO 18611.

What will happen in the case of a spill or someone is splashed with Marine Urea Solution (AUS40)?

  • Always refer to the Marine Urea Solution (AUS40) supplier’s Safety Data Sheet (SDS). 
  • In case of spillage, wipe the area dry and rinse the area with plenty of water.
  • In case someone is splashed with Marine Urea Solution (AUS40), immediately rinse the affected area with water and change out of the wet clothes.

Why does the Marine Urea Solution (AUS40) smell like urine?

A small amount of the urea solution has decomposed into carbon dioxide and ammonia. The ammonia within the Marine Urea Solution gives off its urine smell.

Some urea solutions smell worse than the others, is it due to a higher concentration?

This is a very common misconception. The smell is definitely not an indicator of urea concentration. Everyone’s sense of smell is subjective and highly inaccurate.

This is why it is always better to rely on scientific methods to determine the urea solution’s concentration. You can refer to the supplier Certificate of Assessment (COA) to find out more on the marine urea solution concentration.

What’s the freezing point of Marine Urea Solution (AUS40)?

The freezing point of Marine Urea Solution (AUS40) is approximately 0°C.

For more information on marine urea solutions and their handling, contact our expert team.

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