e-ammonia

The main feedstocks for e-ammonia production are low-emissions electricity, water, and air. Nitrogen (from air) is combined with hydrogen (separated from water using electrolysis, powered by low-emissions electricity) to produce e-ammonia.

Mature low-emissions electricity generation technologies like solar, wind, and hydro are commercially available, but large-scale build-out is needed to support e-ammonia production. The potential use of nuclear power for e-ammonia production remains uncertain and an area for further exploration. Scaling up low-emissions electricity generation is the main feedstock challenge for e-ammonia production.

While water is globally plentiful, accessible fresh water makes up just under 1% of the planet’s water. Of the remaining water, almost 99% is seawater, which is accessible and can be purified by desalination – but the briny discharge requires sustainable disposal.

The air is an abundant source of nitrogen that can be used for e-ammonia production. Air separation technology is also commercially available and scalable.

Both desalination and air separation add some electricity consumption and cost, but to a lesser extent than electrolysis. The main feedstock challenge for producing e-ammonia is the build-out of low-emissions electricity generation at scale.

E-ammonia is produced by combining nitrogen (from air) with hydrogen that has been separated from water using electrolysis powered by low-emissions electricity. This production process has only recently become viable due to the widespread upscaling of electrolysis.

The electrolyzer stack is the core technology needed to split water into oxygen and hydrogen. Global electrolyzer production today is challenged by a scarcity of raw materials, the low stack manufacturing technology maturity and capacity, and the need to produce replacement stacks (current stacks have an average lifespan of 3-12 years).

Additionally, substantial infrastructure for dedicated low-emissions electricity is required to generate hydrogen via electrolysis at an industrial scale. However, the build-out of low-emissions electricity is constrained by issues like the expansion of electricity grids, availability of raw materials such as copper, and competition from other sectors.

The air separation unit technology used to obtain nitrogen from air is both scalable and effective. Finally, the Haber-Bosch process used to produce ammonia from nitrogen and hydrogen has been industrialized and scaled for over a century.

The primary challenges to the advancement of e-ammonia synthesis therefore lie in expanding low-emissions electricity infrastructure and increasing the manufacturing capacity of electrolyzer stacks. 

Ammonia is handled globally as a commodity today, and several ammonia bunker vessel design concepts have been developed. However, there are still gaps to be closed in developing standard processes for safe handling, storage, and bunkering of ammonia as a maritime fuel.

Development of main and auxiliary ammonia engines, as well as ammonia-powered fuel cell technologies, is still ongoing. The first dual-fuel ammonia engines, both two- and four-stroke, are commercially available, but there is no operational experience from first movers using ammonia as a fuel on ships.

Fuel cells and catalytic ammonia crackers are also under development for marine applications. Systems for ammonia emissions abatement and ammonia release management are commercially available. While solutions for managing nitrous oxide (N2O) emissions from engines using low-pressure fuel injection still need to be developed, ammonia-fired boilers are not yet commercially available. However, ammonia-fired burners are currently used in emission control systems to help mitigate ammonia releases.

The MMMCZCS, together with partners, has released several studies and concept ship designs relating to ammonia as fuel.

Industry must address the potential safety hazards which correspond with using ammonia as an alternative fuel. Because ammonia is highly toxic, onboard safety and operations present a crucial challenge for this fuel pathway. Accordingly, risk assessments and their impact on vessel design and cost are key areas of investigation to enable maturation of this pathway. Onboard safety and operations are crucial for a successful adoption of ammonia-fueled vessels.

Currently, liquefied petroleum gas (LPG) carriers handle the safe management of ammonia as a cargo; however, a vessel fueled by ammonia will introduce different risks, including crew exposure to ammonia leakages or emissions. Understanding risks to crew and the safeguards that can be implemented to reduce these risks is therefore paramount.

To protect the crew against safety risks, comprehensive and regular training must be developed and rolled out. The maritime industry must ensure that operating procedures, safety management arrangements, and crew training keep pace with innovation. In the coming years, crew need to be trained in how to handle, store, and manage ammonia safely and in how to operate technically advanced propulsion systems.

Precautions including inherently safer ship design and increased automation will further help to maintain safety risks within tolerable limits. Risk assessments and accompanying impacts on vessel design and cost are also key areas for investigation.

As ammonia contains no carbon, its combustion does not produce CO₂ emissions. However, ammonia-fueled engines require a small quantity of pilot fuel, which may produce some CO₂ if the pilot fuel is carbon-based.

Ammonia-fueled internal combustion engines are a relatively new technology, and therefore, we have limited access to robust information about the emissions produced by these engines. Potential emissions include the greenhouse gas nitrous oxide (N₂O), toxic uncombusted nitrogen oxides (NO_x), and ammonia slip.

Recent results from trials of an ammonia-fueled two-stroke engine with high-pressure liquid injection suggest that emissions can be managed using engine tuning and a selective catalytic reduction (SCR) system. Meanwhile, a four-stroke engine with low-pressure gas injection will achieve a 70% net reduction in greenhouse gas emissions, due to formation of N₂O and higher consumption of pilot fuel oil. Emissions from ammonia-fed boilers and fuel cells are currently unknown.

The regulatory environment for ammonia as a maritime fuel still requires considerable development. For instance, there is no ammonia fuel standard (e.g., on purity), which is needed to allow the use of this fuel. Detailed prescriptive rules for ammonia as a fuel are not incorporated into the International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels (IGF Code), meaning that ammonia-fueled vessel design projects currently must undergo an alternative process for design approval by the flag state. Several classification societies have released guidelines for ammonia-fueled vessels; however, these guidelines are not unified in their approaches and requirements. The International Maritime Organization (IMO) has recently approved draft interim guidelines for the safety of ships using ammonia as fuel, but these guidelines should be considered high-level and still under review. Changes to the International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) have also recently been introduced to accommodate ammonia as a fuel for gas carriers.

At the same time, the IMO is advancing its development of well-to-wake-based regulations to promote the use of sustainable fuels, including e-ammonia. Regulating the climate impact of fuel use from a life-cycle (well-to-wake) perspective offers the industry the opportunity to establish sustainable fuel production and consumption patterns. Such regulation can help mitigate the risk of shifting climate impact from the downstream (tank-to-wake) segment of the value chain to the upstream (well-to-tank). This is a crucial consideration for alternative marine fuels, as a significant portion of their climate impact is associated with upstream activities (see also tiles for feedstock availability and fuel production). However, many elements of these regulations remain to be discussed and finalized, including certification, sustainability criteria, rules for electricity production, and implementation in the IMO mid-term measures.

The European Union (EU) has made progress with the introduction of the EU Emissions Trading Scheme and the FuelEU Maritime regulation, which may promote the uptake of e-ammonia. With that said, some aspects relating to the certification of e-ammonia remain to be resolved.