This section relates to the relevant consideration for the early adaption of e-ammonia as an alternative fuel.
The main feedstock for e-ammonia production are low emission electricity, water, and nitrogen. For low emission electricity, mature technologies like solar, wind and hydro are in place but not yet available at the scale needed. Key challenges for producing e-ammonia therefore remains the availability of power-to-X (P2X) technology and scaling of production of low emission electricity. Main cost drivers for e-ammonia production are the costs for low emission electricity, along with the cost of the electrolyzers needed for hydrogen production. The potential use of nuclear electricity for e-ammonia production remains uncertain and an area for further exploration.
Ammonia synthesis using natural gas as feedstock is a mature technology, but the use of renewable electricity as feedstock for producing the needed hydrogen is new and a cost driver. Commercially mature electrolyzers (such as alkaline and PEM) are currently too expensive and inefficient to make e-ammonia a competitor to other alternative fuels and fossil fuels. Global electrolyzer production capacity is not ready for massive power-to-X roll-out in large scale and record pace construction of new large-scale ammonia plants is required if e-ammonia is to have a significant role in decarbonizing shipping.
Fuel storage, logistics & bunkering
Ammonia is transported globally as a commodity (~20 million ton/year), but port infrastructure such as terminals and bunkering facilities must be significantly expanded to handle potentially hundreds of millions of shipping tons per year. The new technologies and the new requirements create a need for standards around hardware, bunkering and safety procedures.
Onboard energy storage
& fuel conversion
The development of tank storage solutions for larger ammonia volumes, engine, and fuel cell technologies are ongoing. Dual-fuel ammonia engines are being developed but are not finally proven or commercially available yet. It also means that the required post-combustion emission reduction technologies are currently unknown. Solid Oxide Fuel Cells (SOFC) may run on ammonia directly, but SOFCs are significantly less mature and cannot be considered an ammonia-enabler for first movers. Boilers using ammonia as a fuel are under development but not yet commercially available.
Onboard safety & operations
Ammonia is highly toxic which makes risk assessments and impact on vessel design and cost key areas of investigation.
Onboard safety and operations are crucial for safe operation of ammonia fueled vessels. Currently, LPG carriers handle the safety management of ammonia as a cargo, but a vessel fueled by ammonia will introduce different risk including crew exposure from ammonia leakages or emissions. Risk management incl. quantitative risk assessments and human factor are required to enable detailed design and requirement specification for materials, components, location of systems like storage tanks, fuel gas supply system, and safety management systems.
Combustion of ammonia does not produce CO2 emissions as no carbon is contained in the fuel – except from the quantity of needed pilot fuel if it is carbon-based. Knowledge of, and experience, with emissions from ammonia internal combustion engines is limited. However, the potential exists for emissions of both N2O (a potent GHG combustion byproduct) and NH3 slip (highly toxic). Until fully developed and validated ammonia engines are available, the requirements for emission reduction technologies onboard are unclear. Based on potential emission scenarios, there will be a need for a selective catalytic reduction (SCR) system to remove NOx, potentially an N2O catalyst, as well as an additional catalyst or technology to remove ammonia slip. Based on the uncertainty of actual emissions from the engines under development, there are currently major challenges that need to be overcome before this fuel pathway can be matured.
Regulation & certification
On the regulatory side, some key outstanding concerns are present for using ammonia as a fuel. There is no ammonia fuel standard (on e.g. purity) which is needed to allow the use of ammonia. There is also no well-to-wake greenhouse gas quantification for ammonia developed in appropriate regulatory bodies such as the International Maritime Organization (IMO) or European Union (EU). Detailed prescriptive rules for ammonia as a fuel are not incorporated into the IGF code, requiring an alternative design approved by the Flag State for current ammonia-fueled vessel design projects. Classification societies have released guidelines for ammonia-fueled vessels; however, they are not consistent or unified in their approaches or requirements
Life cycle assessment policy needs to be developed. Regulating the climate impact of fuel use from a life cycle perspective offers the industry the opportunity to establish sustainable fuel production and consumption patterns. By regulating the upstream (well-to-tank) climate impact, fuel users can select fuels with solid sustainability credentials. Regulation from a life cycle perspective also reduces the risk of burden shift of climate impact from the downstream (tank-to-wake) part of the value chain to the upstream. This is an important consideration for alternative marine fuels whereby much of the climate impact resides in well-to-tank activities.
Ammonia as a marine fuel: Prospects for the shipping industry - Documentation of assumptions for NavigaTE 1.0 (2021)