Safety of ammonia for use in ships

Banner Ammonia Safety 100s

Although ammonia has been transported by ship onboard liquefied gas carriers for decades, its application as a marine fuel remains widely uncharted, with technologies such as ammonia-fuelled internal combustion engines yet to be proven at scale.

Some shipping companies have already placed orders for ammonia-fuelled vessels, underlining ammonia’s potential as an alternative to fossil fuels. However, its adoption introduces substantial safety and operational challenges, including toxicity, corrosiveness, and the need for specialised fuel systems and engine designs.

Addressing these risks through robust safety protocols, regulatory frameworks, and crew training is essential to ensure the safe and effective integration of ammonia into marine propulsion systems.

Therefore, in order to support national administrations and industry in the decarbonisation transition, EMSA has finalised a series of reports into the safety of ammonia for use in ships.

Task 1 of this study presents an extensive analysis of ammonia properties and characteristics and how these are applicable as marine fuel. The main hazard of ammonia in comparison to other conventional and alternatives fuels is toxicity (can start being an occupational hazard from low concentrations (20 ppm for 8 hours exposure - 50 ppm for 15 min exposure) and become a threat for life when in higher concentrations (300 ppm for 30 min exposure - Immediately Dangerous to Life or Health)), and corrosivity. This study provides an analysis of the toxicity and exposure limits of ammonia comparing several regulatory frameworks. Aside from toxicity, the general behaviour of ammonia was investigated, how this reacts with air and water and how that affects other materials with its corrosive nature and through the stress corrosion cracking.

This report includes a review of the current onshore and offshore regulatory framework related to the use and transport of ammonia and acknowledges that there is still work to do to address properly the safety hazards of ammonia as fuel.

Task 2 includes the identification of critical equipment and failure modes and a qualitative evaluation of the reliability of ammonia systems. In depth fault tree analysis was conducted through interviews with Subject Matter Experts (SME) in naval architecture, ammonia fuel, engine makers and bunkering equipment vendors. Several reliability models were constructed based on information from LPG application modified to consider ammonia fuel applications.

EMSA NH3SAFE Part 3 Risk assessment of a generic ship design

Task 3 describes the results of an hazard and operability study of a generic ammonia fuel supply system from the fuel tank to the internal combustion engine complemented by consequence modelling of potential ammonia leaks through CFD simulation.

Task 4 and Task 5 describe the results of similar HAZID exercises upon the use of ammonia as fuel in specific ship designs - a Newcastlemax dry bulk carrier and a mega ro-ro, respectively - including the risk assessment of scenarios when there are simultaneous operations in ports.

Pages from EMSA NH3SAFE Part 4 Risk assessment of a bulk carrier ship design

This final report consolidates the study’s findings and recommendations for future regulatory developments. It highlights the importance of using risk and reliability methods for the identification of top risk contributors and lists best practice recommendations in line with current industry standards.

In addition, the report highlights as gaps considerations related to the long-term toxicity risks from chronic low-level ammonia exposure, the lack of performance standards for ammonia safety systems, the lack of harmonised guidance for gas dispersion simulations and the lack of technical and performance criteria for the design, integration and maintenance of the ammonia release mitigation system, amongst others.

The reports made available in this section, developed concurrently with the now-approved IMO Guidelines on the Safe Use of Ammonia as Marine Fuel (MSC.1/Circ.1687), underscored the necessity of a more profound mutual understanding regarding the system’s boundaries and requirements for the safe integration of systems across diverse technology providers. This groundbreaking work offers a valuable reference for stakeholders engaged in addressing this crucial challenge.