Safe Use of Hydrogen and Ammonia as Fuel

Setting Safety Requirements for Zero-Carbon Ships

By Carlo Aiachini , IACS Safe Decarbonisation Panel Chair

The International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC) at its 80th meeting (held in July 2023) adopted a revised strategy on the reduction of greenhouse gas (GHG) emissions from ships, revoking the 2018 initial IMO GHG Strategy.

The revised strategy includes the following levels of ambition:

• Carbon intensity of ships is to decline through further improvement of the energy efficiency of new ships;
• Carbon intensity of international shipping to is decline, with a goal to reduce CO2 emissions per transport work, as an average across international shipping, by at least 40% by 2030, compared with 2008;
• Increase uptake of zero or near-zero GHG emission technologies, fuels and/or energy sources, with those to represent at least 5%, striving for 10%, of the energy used by international shipping by 2030; and
• That GHG emissions from international shipping peak as soon as possible and reach net-zero GHG emissions by or close to 2050.

The 2023 IMO GHG Strategy also introduces the following indicative checkpoints to reach net-zero GHG emissions from international shipping:

• Reduce the total annual GHG emissions from international shipping by at least 20%, striving for 30%, by 2030, compared with 2008;
• Reduce the total annual GHG emissions from international shipping by at least 70%, striving for 80%, by 2040, compared to 2008.

With only seven years left before the first deadline for reducing carbon intensity by 40% compared with 2008, technological innovation and the introduction of zero carbon fuels and alternative energy sources for international shipping will be key factors in achieving the ambitious overall target.

Codes and guidelines

The IMO Maritime Safety Committee (MSC), via its Sub-Committee on Carriage of Cargoes and Containers (CCC), has already developed the International Code of Safety for Ships using Gases and other Low-flashpoint Fuels (IGF Code), the Interim Guidelines for the Safety of Ships using Methyl/Ethyl Alcohol as Fuel, the Interim Guidelines for the Safety of Ships using Fuel Cell Power Installations, and Interim Guidelines for use of LPG Cargo as Fuel.

It is now also developing Interim Guidelines for the Safety of Ships using Hydrogen as Fuel, Interim Guidelines for the Safety of Ships using Ammonia as Fuel, and Interim Guidelines for Ships using Low-Flashpoint Oil Fuels.

In this context, IACS developed two gap analyses of the IGF Code in respect of the hazards related to the use of hydrogen and ammonia as fuels and used them to provide input to the IMO CCC Correspondence Group convened to progress the development of the above new guidelines.

The results of the two gap analyses were submitted to the 9th session of the IMO CCC Sub-Committee (CCC 9), in the format of two commenting papers (CCC 9/3/14, CCC 9/3/15) to the Correspondence Group report.

CCC 9 met on September 20-29, 2023, and established a Working Group on Development of Technical Provisions for Safety of Ships using Alternative Fuels, where the Interim Guidelines for the Safety of Ships using Hydrogen as Fuel and Interim Guidelines for the Safety of Ships using Ammonia as Fuel were further developed with IACS’ contribution.

Interim Guidelines for the Safety of Ships using Hydrogen as Fuel

During the discussion in the Working Group, it was highlighted that while the IGF Code is a good starting point and many of its requirements would also be applicable to hydrogen, the use of hydrogen presents additional peculiar hazards that are to be addressed specifically. In particular, the capability of hydrogen to leak through the container by permeation, its wide flammability range and low ignition energy bring new risks of accumulation of leaked hydrogen and explosion caused by ignition sources not normally considered for other gases, like electrostatic discharge.

Consequently, the following considerations, inter alia, were made:

• Use of hydrogen as fuel should be subjected to a holistic risk assessment.
• Hydrogen storage tanks should be protected from external damage caused by collision or grounding, according to the requirements for LNG tanks in Chapter 5 of the IGF Code.
• All hydrogen storage tanks should, by default, be arranged on the open deck. Designs with tanks placed under deck would require special consideration by the Administration with focus on particular risks.
• The Fuel Preparation Room (FPR) should be located in an open deck area providing natural ventilation and unobstructed relief of leakages. If such equipment is to be arranged in an enclosure or in a space below deck, then the arrangement should be subject to the special consideration and satisfaction of the Administration.
• Hydrogen stored respectively in a liquefied or compressed state brings very different risks. Therefore, the relevant detailed requirements are to be adapted and separated. For example, in the case of liquefied hydrogen – which has a temperature of -253°C at atmospheric pressure – special attention should be paid to the condensation of oxygen from air on cold surfaces (including those of drip trays) which poses a risk of fire in case of contact with any combustible material, whereas for compressed hydrogen, special attention should be paid to its capability to permeate the container causing embrittlement of the container material and a continuous leak to the outside.
• Only gas-safe machinery spaces in accordance with the IGF Code should be accepted, and the ESD-protected machinery space concept should only be accepted in the context of an alternative design according to SOLAS Regulation II-1/55.

Interim Guidelines for the Safety of Ships using Ammonia as Fuel

The Working Group also addressed the development of the Interim Guidelines for the Safety of Ships using Ammonia as Fuel. It was highlighted that the use of ammonia constitutes a different risk profile compared with LNG and requires careful consideration of safety provisions addressing the properties of ammonia, including toxicity and corrosivity.

A series of informal meetings held in the margins of the Working Group with many of the WG attendees were very useful in understanding the properties of ammonia, the industrial practice for handling ammonia and the Group’s view on the risk of human exposure to toxic gas.

Due to time constraints, the Working Group was unable to consider the draft guidelines in their entirety, but discussed and agreed on some key principles to take into account, including:

Only refrigerated ammonia and semi- refrigerated ammonia should be considered in the guidelines as a first stage, while the use of pressurised ammonia would be made possible through the alternative design process.

The design should be such that during normal operations there is no presence of ammonia in areas and spaces to which people have access.

Ammonia release may occur for safety reasons, but release mitigation measures should be considered.

Arrangement of safe refuge spaces (and PPE) should be considered in the event of large ammonia releases.

Only the gas-safe machinery space concept in accordance with the IGF Code should be accepted, and the ESD-protected machinery space concept should only be accepted in the context of an alternative design according to SOLAS Regulation II-1/55.

The development of the draft Interim Guidelines will be continued by a new Correspondence Group, in which IACS participates, and then by an Intersessional Working Group to be held in September 2024.?

New UR

IACS has recently published a new Unified Requirement (UR H1) on the control of ammonia releases in ammonia fuelled vessels, which – while respecting the IMO agreed principle of no release under normal conditions – sets thresholds for concentration of ammonia in manned spaces in the event that ammonia is released (e.g. for safety reasons) and establishes the actions to be taken when they are exceeded.

The IACS Project Team which carried out the gap analysis of the IGF Code in respect of the hazards related to hydrogen is now developing requirements for materials and testing of piping systems intended for hydrogen service, as well as hydrogen Type C tanks and swappable tanks, i.e. tanks intended to be disembarked, filled ashore and embarked when refilled.

The IACS Project Team which carried out the gap analysis of the IGF Code in respect of the hazards related to ammonia is now developing requirements for ammonia treatment systems, i.e. systems intended to reduce the quantity or concentration of the ammonia being released.

Finally, IACS has activated a new Project Team to develop guidance and recommended good practice on simulating dispersion of gas releases (under normal and emergency scenarios) using mathematical models (e.g. Computational Fluid Dynamics (CFD), DNV PHAST, etc.) for ships using hydrogen or ammonia as fuel, enabling evaluation of the extension of areas where hazardous concentrations of toxic or flammable gases are expected to occur in specific scenarios and which require special precautions.

IACS will continue to collaborate with IMO and in parallel will consider the opportunity of developing its own Resolutions and Recommendations to address the safety aspects of these and other new technologies and fuels.?

Read more from IACS' 2023 Annual Review

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