The maritime industry, which accounts for nearly 3% of global greenhouse gas (GHG) emissions, is under growing pressure to reduce its environmental impact. As governments, regulatory bodies, and shipping companies seek cleaner alternatives to traditional fossil fuels, ammonia has emerged as one of the most promising green fuels for the future of shipping. This article provides a comprehensive introduction to ammonia as a green fuel, its potential in the maritime industry, and the challenges that must be overcome to make ammonia-powered shipping a reality.
The Need for Green Fuels in Shipping
Shipping is an essential part of the global economy, responsible for transporting around 90% of the world’s goods. However, it has traditionally relied on heavy fuel oil (HFO), a carbon-intensive and polluting fuel, leading to significant GHG emissions. The International Maritime Organization (IMO) has set ambitious targets to reduce emissions by 50% by 2050 compared to 2008 levels, with a long-term goal of full decarbonization.
To meet these targets, the industry is exploring various alternative fuels and technologies. Among them, ammonia has garnered significant attention due to its zero-carbon combustion and potential to help the industry transition to a more sustainable future.
What is Ammonia?
Ammonia (NH₃) is a compound made up of nitrogen and hydrogen. It is a colorless gas with a pungent odor and has been used for decades as a chemical feedstock in the production of fertilizers, explosives, and other industrial products. It can be synthesized through a process known as the Haber-Bosch process, where nitrogen is extracted from the air and combined with hydrogen at high temperatures and pressures.
Green Ammonia Production
To qualify as a truly “green” fuel, the ammonia used in shipping must be produced without carbon emissions. This can be achieved by using renewable energy sources like wind, solar, or hydropower to produce hydrogen via electrolysis (a process that splits water into hydrogen and oxygen) and then synthesizing ammonia from this green hydrogen. This results in green ammonia, which is produced with minimal or zero GHG emissions.
In contrast, most ammonia production today relies on natural gas as a hydrogen source, making it carbon-intensive. To realize ammonia’s potential as a green fuel, the industry must shift to green ammonia production methods.
Why Ammonia is Considered a Green Fuel for Shipping
Credit: https://spectrum.ieee.org/why-the-shipping-industry-is-betting-big-on-ammonia
1. Zero Carbon Emissions
Ammonia is one of the few alternative fuels that produce zero carbon dioxide (CO₂) emissions when burned. Unlike conventional fuels such as HFO, diesel, or liquefied natural gas (LNG), ammonia does not contain carbon, meaning it releases no CO₂ when combusted in an engine or burned in a fuel cell. This makes it an attractive option for decarbonizing the maritime industry.
2. Abundant and Scalable
Ammonia is one of the most widely produced chemicals in the world, with a well-established global production and transportation infrastructure. Its availability, combined with the potential to produce ammonia using renewable energy, makes it scalable for widespread use in the shipping industry.
3. Energy Density
While ammonia has a lower energy density compared to traditional fossil fuels, it is still considered a viable option for long-distance shipping. Ammonia’s energy density is higher than that of other green fuels, such as hydrogen in its compressed or liquid form, making it more suitable for use in large vessels that travel long distances.
4. Existing Infrastructure
Ammonia is already produced, stored, and transported in large quantities for industrial purposes, meaning the infrastructure needed to support its use as a marine fuel is partially in place. This includes ammonia storage facilities, transport networks, and safety protocols that can be adapted for the maritime sector.
5. Versatile Applications
Ammonia can be used in various ways to power ships. It can be burned in internal combustion engines (after certain modifications) or used in fuel cells to generate electricity. Research is also underway to develop more efficient ammonia-powered engines and improve fuel cell technology.
How Ammonia Can Power Ships
There are two main pathways for using ammonia as a marine fuel:
1. Ammonia Combustion in Engines
One way to use ammonia as a fuel is by modifying existing internal combustion engines (ICE) to run on ammonia. This approach has the advantage of leveraging existing engine technologies, which could be retrofitted to run on ammonia with relatively minor modifications. In such engines, ammonia would be combusted to produce heat and mechanical energy, similar to how fossil fuels are burned in conventional engines.
However, ammonia combustion poses certain challenges, such as:
- Low flame speed: Ammonia has a slower combustion rate compared to traditional fuels, which can affect engine performance.
- NOx emissions: While ammonia does not produce CO₂, its combustion can result in the formation of nitrogen oxides (NOx), which are harmful pollutants. These emissions can be mitigated with after-treatment technologies such as selective catalytic reduction (SCR) systems.
2. Ammonia Fuel Cells
Ammonia can also be used in fuel cells to generate electricity, which can then power electric propulsion systems on ships. Fuel cells offer a cleaner and more efficient way to use ammonia as a fuel since they do not involve combustion and produce fewer pollutants. In ammonia fuel cells, ammonia is split into nitrogen and hydrogen, and the hydrogen is used to generate electricity.
While fuel cells are more efficient than combustion engines, this technology is still in the early stages of development for maritime applications. Significant research and development are required to make ammonia fuel cells commercially viable for large vessels.
Benefits of Ammonia as a Marine Fuel
1. Decarbonization Potential
The use of green ammonia can significantly reduce or even eliminate CO₂ emissions from shipping, making it a key enabler for meeting IMO decarbonization targets. Unlike other green fuels like biofuels or LNG, which still emit carbon when burned, ammonia provides a zero-carbon solution.
2. Energy Storage and Transportation
Ammonia is easier to store and transport compared to hydrogen, which is another potential green fuel for ships. Ammonia can be stored as a liquid at relatively low pressure, making it more practical for use in maritime applications than compressed or liquefied hydrogen.
3. Compatibility with Existing Infrastructure
The fact that ammonia is already widely produced and transported for industrial purposes makes it easier to integrate into the existing maritime fuel supply chain. Ports and bunkering stations could be adapted to handle ammonia with fewer challenges compared to other alternative fuels.
4. Lower Cost Compared to Hydrogen
Ammonia is more cost-effective to produce, store, and transport than hydrogen, making it a more viable long-term solution for the shipping industry.
Challenges of Ammonia as a Marine Fuel
While ammonia presents numerous advantages as a green fuel, there are several challenges that need to be addressed before it can be widely adopted in the shipping industry.
1. Toxicity
Ammonia is highly toxic, and exposure to even small amounts can be harmful to human health. The maritime industry will need to implement strict safety protocols and regulations to handle, store, and transport ammonia safely. This includes ensuring that seafarers and port workers are trained to deal with ammonia-related risks.
2. Energy Efficiency
Ammonia has a lower energy density than conventional fuels, which means that ships will need to store larger quantities of ammonia to achieve the same range. This could impact the design of ships, as they would require more space for fuel storage or more frequent refueling stops.
3. NOx Emissions
While ammonia does not produce CO₂ emissions, it can generate NOx during combustion, which contributes to air pollution. Developing technologies to mitigate NOx emissions, such as exhaust gas cleaning systems, will be essential for ammonia-powered ships to meet environmental standards.
4. Green Ammonia Production
Currently, most ammonia is produced using fossil fuels, which defeats the purpose of using it as a green fuel. To make ammonia a truly sustainable option, the industry must invest in green ammonia production, which relies on renewable energy sources. Scaling up green ammonia production to meet global shipping demands will require significant infrastructure development and investment.
The Future of Ammonia in Shipping
The potential of ammonia as a green marine fuel is promising, but realizing this potential will require collaboration across the maritime industry, energy producers, governments, and regulatory bodies. Research and development efforts are already underway, with several pilot projects exploring the use of ammonia-powered vessels.
In addition, regulatory frameworks and safety standards will need to be established to ensure the safe and efficient use of ammonia in shipping. The IMO and national maritime authorities are expected to play a crucial role in developing guidelines for ammonia as a marine fuel.
Conclusion
Ammonia has the potential to play a significant role in the decarbonization of the shipping industry. Its zero-carbon emissions, scalability, and existing infrastructure make it a strong contender among alternative fuels. However, challenges related to safety, energy efficiency, NOx emissions, and green ammonia production must be addressed for ammonia to become a mainstream fuel for ships. As research continues and technologies evolve, ammonia may soon help the maritime industry achieve its ambitious sustainability goals.