Case Study


Fluechem were approached by a Very Large Crude Carrier (VLCC) operator to support in ensuring a vessel had the required certification to access United States waters, due to concerns over the AUS40 on board.

A number of new vessels had been delivered in 2020 with AUS40 onboard and there were concerns over whether this was of acceptable quality for entry into the North American Nitrogen Oxide (NOx) Emission Control Area (ECA), as it had been onboard for more than a year and exposed to high temperatures. We were approached to provide technical and regulatory support and help to secure an Ocean Transiting Vessel Nox Compliance Certificate (OTVNCC).

The Challenge

The vessel team onboard and ashore had limited technical and operational experience in using AUS40

with the Selective Catalytic Reduction (SCR) system onboard and were not familiar with the requirements detailed in the US Coast Guard (USCG) guidelines for compliance with MARPOL prevention of air pollution from ships. Furthermore it was not clear what the current status and quality of the AUS40 was onboard.

The Fluechem support team initially carried out a review of the technical specification of the SCR system in addition to the historical operational data and provided some AUS40 Refractometers so the urea concentration of the AUS40 onboard could be verified against the ISO 18611 standard.

Unfortunately the initial test indicated that the AUS40 onboard was marginally outside the urea content limit of the ISO standard and hence could be in breach of the SCR operating parameters.

The Solution

The Fluechem team developed an onboard AUS40 recirculation and testing programme, including a pH measurement protocol, to prepare a contingency for the addition of a buffer additive solution, if the AUS40 could not be brought within the ISO standard specification. After completion of the programme, the AUS40 urea content was measured at the limit of the ISO standard specification and considered suitable for testing the performance of the SCR system.

Verification and Validation

The output from the SCR system test and NOx Verification Method were reviewed by the Fluechem Independent Technical Authority against the NOx emission limits detailed in the vessels IAPP Certificate and associated EIAPP Certificate. This was then validated and verified against the components outlined in the approved Engine Technical File and Record Book of Engine Parameters.


Upon completion of the review, the Fluechem Technical Authority confirmed that, based on the evidence reviewed, the engines and associated equipment, including the current AUS40 onboard, was compliant with the IMO TIER III Regulations to abate NOx emissions and a OTVNCC was issued to present to the USCG as independent evidence of ongoing compliance with MARPOL VI. The vessel entered the North American ECA without any delays or compliance issues and continues to use the AUS40 stock onboard, subject to agreed testing protocols with backup Fluechem support team.

This was made possible due to the many years of global experience working with MARPOL VI compliance matters to support our customers under the company’s Vision to “Deliver practical and cost effective solutions for marine customers to support the reduction of environmental emissions from ships promoting cleaner air and water for all”.

AUS40 for Shipping