Ammonia as a renewable fuel for the maritime industry.
The International Maritime Organization issued its Initial GHG Strategy, committing the global shipping industry to emission reductions that cannot be achieved with carbon-based fuels. This single action is the regulatory trigger that unleashes a three-decade transition to carbon-free liquid fuels like ammonia. The target date for this 50% reduction in emissions is 2050 but, given the long economic life of ocean vessels, the transition must begin immediately.
Maritime classification societies, including Lloyd’s Register and DNV GL, have published in-depth analyses of ammonia’s potential role in this transition, alongside other carbon-neutral fuels. Lloyd’s Register declared that ammonia “appears the most competitive” of all sustainable liquid fuels. DNV GL predicted that carbon-neutral liquid fuels would overtake oil-based fuels in the global shipping market by 2050, 39% to 33%. For ammonia to meet this demand, an additional 200 million tons per year must be produced, without fossil feed stocks.
The International Transport Forum, the OECD’s “think tank for transport policy,” announced that “currently known technologies could make it possible to almost completely decarbonise maritime shipping by 2035,” based on achieving a 70% mix of ship using ammoaltn or hydrogen fuel.
In the coming year, we can expect much more in-depth analysis of the potential for ammonia fuel from experts across the shipping sector. This will require moving from theoretical desktop studies to experimental real-world demonstration projects. The first of these pilot projects will be the Dutch consortium, with partnership from Yara, which is developing “an ammonia tanker fueled by its own cargo.
The case for ammonia
Carbon emissions
Ammonia is a compound of nitrogen and hydrogen. As ammonia contains no carbon it does not emit any CO2 when used to fuel an internal combustion engine. This creates the potential for truly zero carbon propulsion. An additional small quantity of pilot fuel is required for combustion however, which should also be zero carbon. However, what must be considered is that most ammonia today is produced from natural gas and so from a lifecycle perspective it is not zero-carbon, which is something the industry needs to address if ammonia is pursued.
Acceptable energy density
One attraction of current fossil-based fuels is their high volumetric energy density. Most alternative fuels are unable to match this, meaning that they would take up valuable cargo space onboard a ship. Ammonia volumetric energy density is broadly similar to methanol and higher than hydrogen, making onboard storage economically feasible, albeit not as compact as the heavy fuel oil (HFO) used today.
Relatively easy to handle
Ammonia is often compared with hydrogen. Both are stored in liquid form, hydrogen requiring cryogenic tanks maintained at -253°C, while ammonia requires less cooling and can be stored at temperatures of around -33°C. Ammonia is manufactured from hydrogen, so for zero carbon ammonia we need ‘green’ hydrogen manufactured using renewable energy.
Hydrogen transport
Hydrogen can also be used as a fuel for shipping or other purposes; however, the sophisticated cooling equipment and mitigation of hazards make hydrogen expensive to transport. Carrying ammonia has advantages over hydrogen in that it is liquid at ambient conditions, requiring lower storage volumes. The costs of hydrogen transportation may be reduced by manufacturing ammonia from hydrogen at the source, transporting the resulting ammonia and then reforming back to hydrogen at the destination, but more work is needed to calculate this cost reduction.
Economics have long-term potential Ammonia is a global commodity with transparent pricing, so a market already exists. The bulk of current supply is ‘grey’ ammonia, manufactured from hydrogen created from natural gas, which generates significant CO2 emissions. Shipping’s goal is to produce ‘green’ ammonia from renewable energy. While this will be much more costly in the short-term, prices should fall substantially as production is scaled up.
The major challenges are land-based
The focus is often on carbon emissions generated from a ship’s engine and ancillary systems onboard. Yet substantial emissions are also generated in the production and supply of fuel, through extraction of energy sources, fuel manufacture, transport and storage at port. To avoid simply shifting the problem upstream, the shipping industry needs to consider the whole supply chain.
A 2020 study by University Maritime Advisory Services (UMAS) and the Energy Transitions Commission found that USD 1-1.4 trillion is needed to achieve the IMO’s carbon reduction ambition by 2050. The study also highlighted that around 87% of the total investment is needed in land-based infrastructure and production facilities for low carbon fuels. In many cases the upstream challenges are also tougher to overcome, as they involve many more stakeholders, and these huge infrastructure investments could have significant impacts on people and the environment.
A worldwide ammonia distribution system is already in place, but fuel needs to be available in the right locations at the right volumes. The existing ammonia transport network connects production and storage locations that serve the industrial market; it does not reach ports in a way that would allow ships to bunker.
Perception of ammonia by the wider community, outside fleet operators, will need to change for it to become accepted as a fuel. Port authorities and regulators are presently reluctant to permit bunkering of ammonia due to toxicity hazards, while the reaction of citizens to large scale ammonia storage in ports is untested. Whilst current regulations preclude the use of ammonia as a fuel for shipping, classification societies and other groups are working to assess risk and provide guidance that will lead to new rules and standards.
Safety issues must be addressed
While ammonia is not highly flammable, concentrations in air as small as 0.25% can cause fatalities, making the fuel highly toxic to people. Today’s residual and distillate fuel oils (and even natural gas) all present lower risks than ammonia. Fuel systems must be designed, manufactured, operated and maintained to ensure the safety of the ship crews, port staff and fuel suppliers.
Today’s ships are built to standard configurations in which engines and fuel systems are often in confined spaces on lower decks. The different requirements of ammonia could alter ship layouts or could even lead to complete redesigns.
Handling ammonia onboard ships will require a complete new set of skills and safety procedures. There is a need to understand the potential negative impacts on human lives, water and soil in case of leakage or accidents, and how to mitigate these types of risks. A new safety pathway is therefore needed to adopt ammonia. Luckily there is the possibility to leverage current rules around the transport of ammonia.
In addition, the combustion of ammonia in engines releases nitrous oxide (N2O), a greenhouse gas even more potent than CO2. Thereby, additional equipment will be required onboard to control NOx emissions.
Solution readiness
The shipping industry has carried ammonia as bulk cargo for 100 years and the cargo risks are understood and managed. The fuel was also one of the earliest refrigerants used onboard and remains a popular choice for fishing vessels due to its wide availability, simple manufacturing process and relatively low cost.
However, shipping has no experience of ammonia as a fuel and given the safety challenges, a rigorous process for risk assessment of fuel handling and propulsion systems will be required. Robust safety standards must also be mandated across the entire supply chain.
To enable organisations to make informed choices on the zero-carbon journey, the Marine Solution Readiness Level (MSRL) framework was created. This is a standardised screening assessment that ensures consistency of evaluation across widely different fuels and technologies, enabling evidence-based decision making.
Current readiness levels
Research UMAS, ‘Techno-economic assessment of zero-carbon fuels’ (2020) gives an early indication of the investment readiness of ammonia as a shipping fuel in comparison with other alternative fuels, including hydrogen, methanol, biofuels, and batteries, and fossil fuels such as natural gas and HFO. Fuel is the major component of operating costs and the primary driver of vessel competitiveness. The research used a typical bulk carrier as a case study under a range of scenarios for energy price and total operating cost. A key finding was that ammonia produced from natural gas combined with carbon capture and storage (blue ammonia) is the lowest cost zero-carbon option when considering timeframes to 2050.
The research also reviewed technology readiness, identifying that some aspects of the ammonia delivery chain, including bunkering equipment, tanks and fuel supply systems, are progressing towards detailed design solutions. Other areas, such as procedures and quality standards, ancillary equipment onboard and boilers, were still at concept stage. Since then, we’ve seen developments in propulsion progressing rapidly and engine manufacturers are now announcing prototypes and pilot projects.
The UMAS research also provided high-level indications of community readiness in relation to lifecycle emissions and the evolution of the broader energy landscape, showing that green ammonia is one of the best net CO2 performers across the whole lifecycle. For ammonia to transition from industrial commodity to shipping fuel, the right conditions need to be in place across all community dimensions for example, sufficient cross-sector demand, efficient production processes and strong international policy and regulations.