Muammer Akturk, a Senior Marine Surveyor specialising in alternative bunker fuels, recently published an article on ammonia as a marine fuel in his Alternative Marine Fuels Newsletter.

He provides insights into the intricacies of ammonia’s toxicity, the safety measures needed, and the evolving regulations shaping its adoption with the recent discussions at IMO:

Introduction

The maritime sector confronts several significant challenges, primarily due to increasingly stringent regulations concerning emissions and climate change. Factors such as globalization, geopolitical shifts, digitalization, and cybersecurity concerns are further complicating an already intricate operational environment as the shipping industry seeks efficient propulsion and fuel strategies for its global fleet.

The recent alterations to the IMO’s Initial GHG-Reduction Strategy is an international pivot in the maritime industry towards adopting zero-carbon and low-carbon fuels by 2050.

Amidst the diverse array of technological and fuel options currently under consideration by ship designers, builders, owners, and operators, anhydrous ammonia (NH3) is emerging as a potential marine fuel that could be introduced relatively swiftly. It presents a zero-carbon solution (measured from tank to wake) and when considering the entire lifecycle from production to usage (well-to-wake), green ammonia holds the promise of being the ultimate solution. However, it is important to recognize that while ammonia hold great potential, addressing its inherent toxicity remains as a pivotal challenge in harnessing its full benefits.

Properties of Ammonia

Ammonia, under standard atmospheric conditions, exists as a colorless gas and is known for its distinctive strong odor. When subjected to higher pressures, it transitions into a liquid state, simplifying its transportation and storage.

Ammonia exhibits a relatively limited flammability range when compared to some alternative fuels being explored within the shipping industry. However, it is vital to acknowledge its toxicity and high reactivity.

At lower concentrations, ammonia can cause irritation to the eyes, lungs, and skin, while at higher concentrations or upon direct contact, it poses an immediate life-threatening risk. Symptoms encompass breathing difficulties, chest pain, bronchospasms, and, in severe cases, pulmonary edema, characterized by lung fluid accumulation leading to respiratory failure.

Skin exposure to concentrated ammonia can result in severe chemical burns, while contact with the eyes can induce pain, excessive tearing, conjunctival swelling, iris and corneal damage, as well as conditions such as glaucoma and cataracts. Acute exposure to liquid ammonia can manifest as skin redness, swelling, skin ulcers, and frostbite.

Health Risks Associated with Ammonia Fuel Usage

Owing to its harmful properties, ammonia is categorized as a hazardous substance. National standards 

regulate exposure levels and duration, often establishing Permissible Exposure Limits around 50 ppm (parts per million), Recommended Exposure Limits at 25 ppm, and recognizing the Immediate Danger to Life or Health threshold at 300 ppm. Refer to Table 1 for details on exposure duration and associated health effects measured in ppm.

Table 1: Ammonia concentration and Hazard to Human Health

Acute Exposure Guideline Level (AEGL): Ammonia

AEGL 1: Causes irritation but is recoverable immediately when the exposure is stopped

AEGL 2: Cause irreversible or long-lasting health hazards

AEGL 3: Fatal

Potential Source of Ammonia Leakages Onboard

Presently, there are ongoing industry efforts to design and build both an ammonia-powered engine and a corresponding ammonia fuel supply system. These developments facilitate the identification of potential ammonia leaks within a ship’s system. Figure 1 illustrates various sources of ammonia leakage in the ship’s open areas, with the key sources being:

4.1 Sources of Ammonia Leakage in Open Areas

• Ammonia fuel tank PRV open.
• Fuel supply system purge/vent/bleed outlet.
• Ventilation outlets in fuel prep room, TCS, double wall spaces.
• Bunkering manifold in open zones.

4.2 Sources of Ammonia Release in Enclosed Spaces

• Fuel preparation room (FPR).
• TCS (Tank Connection Space).
• Double wall spaces, including GVU room (Gas Valve Unit).
• Enclosed bunkering station (if present).

4.3 Release Sources Under Normal Operating Conditions

• Controlled releases from fuel prep ventilation outlets.
• Purging and venting outlets with safety measures.
• Safety measures include gas detection, alarms, shutdown, and ammonia treatment.

4.4 Release Sources in Emergency Situations

• Uncontrolled release during emergencies, like fires near fuel tanks.
• Large release potentially covering entire ship with harmful ammonia concentration.
• Operation of ammonia treatment facility might not feasibly reduce vast gas release.

Figure 1: Potential Source of Ammonia leakages onboard (Source CCC 9/3/1)

Development of IMO Draft Interim Guidelines for the Safety of Ships Using Ammonia as Fuel

The 9th session of CCC is scheduled to take place from September 20 to 29. Much attention is currently focused on drafting guidelines related to alternative fuels, crucial for the industry’s decarbonization goals. One notable effort is the formulation of interim guidelines ensuring the safety of ships utilizing ammonia as fuel.

These interim guidelines are intended for ships subject to SOLAS Chapter II-1 Part G compliance and should be used alongside the IGF Code, incorporating specific considerations for hazards and fuel properties. Completion of this work is anticipated by the end of 2024.

The safety framework employed in the IGF Code for LNG systems encompasses five core principles:

1. Segregation: Ensuring protection of the fuel tank and installation against mechanical harm and fires.
2. Integrity: Designing the fuel system to minimize fuel leakage.
3. Implementing double barriers in all fuel system components to prevent leaks.
4. Detecting and warning of system leakages, enabling automatic safety responses.
5. Automatically shutting down the fuel supply system upon leakage detection to mitigate potential consequences.

Additional critical safety measures are required to address fuel’s toxicity properties too. A thorough understanding of these unique properties and their impact on risk assessment is vital for implementing effective safety measures to mitigate the risks associated with ammonia as a fuel. This serves as a critical foundation for the development of robust safety regulations.

As depicted in Figure 2, the safety principles outlined in the IGF Code for natural gas can be adapted for ammonia, albeit with substantial modifications to address the heightened toxicity risk in case of containment breach. The existing IGF Code requirements for natural gas do not encompass fuel toxicity, necessitating more stringent safety measures to safeguard against ammonia exposure during normal operation and emergencies.

Figure 2: Ammonia toxicity risk table on IGF Code concept (Source CCC 9.INF7)

Final Thoughts

The utilization of ammonia as a fuel in the maritime industry holds promise for decarbonization efforts. However, it comes with inherent toxicity issues that necessitate careful consideration. Safety guidelines and principles established for LNG systems, while adaptable to ammonia, require substantial modifications to address the elevated toxicity risk. Understanding the unique properties of ammonia, its potential health impacts, and implementing effective safety barriers are fundamental steps in mitigating the associated risks. As the industry progresses towards ammonia as a viable alternative fuel, robust safety regulations and comprehensive safety measures must evolve in parallel to ensure a safe and sustainable transition.

Photo credit: Chris Pagan on Unsplash
Source: Alternative Marine Fuels Newsletter 
Published: 12 September, 2023