Anhydrous Ammonia (NH3) is a colorless, lightweight, and toxic gas. Its chemical structure, lacking carbon, classifies it as a zero-carbon fuel. However, its toxic and flammable properties necessitate specialized handling procedures for both storage and transportation. While primarily utilized in various industrial applications, anhydrous ammonia is also transported via maritime vessels as a cargo commodity, reports GOV.UK.
Advantages of Ammonia
Simplified Storage: Ammonia’s liquid state at a relatively higher temperature of -33°C and ambient pressure eases storage requirements compared to more cryogenic fuels like Liquefied Natural Gas (LNG), potentially reducing the complexity and cost of onboard storage systems.
Carbon-Neutral Potential: When produced using renewable energy sources (often referred to as green ammonia), it offers the potential for carbon-neutrality across its lifecycle, a crucial factor in achieving shipping’s decarbonization goals.
Lower Emissions: Even when considering its entire lifecycle, ammonia offers the prospect of significantly lower emissions compared to currently used marine fuels, contributing to reduced air pollution from shipping.
Environmental Biodegradability: Its rapid dissolution in water and swift biodegradation in the marine environment are positive attributes from an environmental perspective, minimizing the potential impact of spills.
Engine Compatibility: Existing marine diesel engines can be adapted to utilize ammonia as fuel through appropriate modifications. These modifications, however, would require thorough approval from recognized Classification Societies or Organizations to ensure safety and operational integrity.
Established Production: Well-established industrial processes, such as the Haber-Bosch process, already exist for manufacturing ammonia at a large scale, indicating the potential for sufficient fuel production to meet shipping demands.
Safe Transportation History: Ammonia has a long history of being transported as cargo by ships, dating back to at least the 1920s. This established practice has led to the development of best practices and industry standards for its safe handling and transportation.
Associated Challenges
While ammonia presents several advantages as a potential marine fuel, it also has significant challenges that need to be addressed:
- Toxicity: Ammonia is toxic, necessitating the implementation of enhanced safety systems onboard vessels. This includes features like cofferdams (protective buffer spaces) and inerting systems to prevent flammable mixtures. For existing vessels considering retrofitting to use ammonia, the space required for these cofferdams can pose a considerable design challenge.
- Corrosivity: Ammonia is a corrosive substance, which means that specific materials and handling procedures are required for its storage and use to prevent damage to vessel systems and ensure safety.
- Lower Energy Density: Compared to traditional marine fuels, ammonia has a lower energy density. This implies that a vessel would need to carry approximately twice the volume of ammonia to achieve the same range as with diesel fuel. This significantly increased fuel tank capacity can be particularly problematic for retrofit projects on existing vessels where space is limited.
- Production Scalability: While existing industrial systems for ammonia production are large, the current output is primarily geared towards agricultural and industrial uses. To meet the potential demand from the shipping sector, in addition to these existing demands, a substantial increase in global ammonia production capacity would be required.
- Cost Competitiveness: Currently, ammonia is more expensive than traditional fuel types used in shipping. For it to become a widely adopted marine fuel, its production costs would need to become more competitive with conventional fuels or alternative low-carbon options.
Regulations and Guidance
The International Maritime Organization (IMO) has proactively developed interim guidelines for the use of ammonia as a marine fuel. These guidelines are available for ship owners and operators who are planning to construct new vessels or convert existing ones to run on ammonia. This guidance must be utilized in conjunction with the IMO’s International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code).
A key requirement under the IGF Code is the submission of an Alternative Design Arrangement (ADA) to the flag Administration for notification to the IMO. The ADA is a risk-based design evaluation process, permitted under the International Convention for the Safety of Life at Sea (SOLAS), which aims to identify the primary hazards and risks associated with the operation of the alternative fuel and implement mitigation measures to the satisfaction of the flag administration and other relevant stakeholders. Comprehensive guidance on the ADA process is detailed in MSC Circular MSC.1/Circ.1212, and ship owners and operators should adhere to this closely before submitting their proposals to the Maritime and Coastguard Agency (MCA) as part of the plan approval process.
The ADA process typically involves several iterations before final approval, with the number of iterations largely depending on the quality and thoroughness of the initial submission. Therefore, owners and operators are strongly encouraged to ensure their submissions are of a high standard to minimize the number of revisions required to achieve approval and final sign-off. Repeat designs or similar designs that have already undergone the ADA process usually benefit from a significantly shorter approval timeline.
The MCA is actively collaborating with other member states at the IMO to further refine the interim guidelines on the use of ammonia as fuel, with the expectation that they will be reviewed, finalized, and incorporated into the main IGF Code in the future.
For ships below 500 gross tonnage (GT) or those not required to comply with the IGF Code, a similar risk-based process, closely mirroring the ADA process, is outlined in Marine Guidance Note 664 (MGN664). Crew training requirements for alternative low-flash-point fuels, including ammonia, are currently addressed under the IGF training requirements of the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW).
The MCA is currently working with training providers to develop a week-long methanol-specific course for convention-sized vessels, with initial courses expected to be launched by mid-2025. Basic training for the use of ammonia as fuel will be integrated into the UK maritime curriculum from September 2025 as part of the new syllabus developed under the Cadet Training and Modernisation (CT&M) programme. Looking further ahead, the IMO will include training standards for alternative fuels, including ammonia, as part of the comprehensive review of the STCW Convention, with an anticipated timeline of 2030 for these updates.
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Source: GOV.UK
