The global economy would grind to a halt if we would stop shipping goods across oceans. At the same time, ocean shipping is one of the largest contributors to greenhouse gas (GHG) emissions. As an increasing number of companies are trying to bring down the carbon footprint of their supply chains, there is increasing pressure on shipping to decarbonize.
The search for sustainable alternatives has led to the exploration of various fuels, including ammonia. Recent research, such as the 1st Life Cycle GHG Emission Study on the Use of Ammonia as Marine Fuel, highlights the potential of ammonia as a marine fuel, which could reduce GHG emissions and help the shipping industry meet international climate goals.
Why Ammonia?
For several reasons, ammonia (NH3) is emerging as a promising alternative to traditional marine fuels. First, it is a carbon-free molecule, meaning its combustion does not directly emit carbon dioxide (CO2), a key driver of climate change. Second, it has a high energy density and can be stored and transported efficiently, making it suitable for long-distance shipping. There are various ways to produce ammonia, each with a different impact in terms of sustainability.
Life Cycle Analysis of Ammonia
The study from Sphera Solutions delves into the life cycle GHG emissions of ammonia, from production (Well-to-Tank, or WtT) to combustion in marine engines (Tank-to-Wake, or TtW). The combined analysis (Well-to-Wake, or WtW) shows the overall environmental impact ammonia can have compared to conventional bunker fuels.
Ammonia Production Pathways
There are four main production pathways for ammonia:
- Green Ammonia: Produced through electrolysis using renewable electricity. This is the most sustainable pathway, as it involves minimal GHG emissions.
- Blue Ammonia: Produced via steam methane reforming (SMR) or autothermal reforming (ATR) with carbon capture and storage (CCS). This pathway reduces emissions by capturing and storing CO2 during the production process.
- Turquoise Ammonia: Produced via pyrolysis, which has a lower carbon intensity but emits GHGs depending on the energy source used.
- Grey Ammonia: Produced via SMR or ATR without CCS, leading to high GHG emissions similar to traditional fossil fuels.
Each pathway has varying GHG intensities, with green ammonia showing the greatest potential for emission reductions. For example, ammonia produced via electrolysis has a base GHG emission rate of 20 g CO2-eq/MJ, compared to 122 g CO2-eq/MJ for grey ammonia produced via SMR without CCS.
GHG Reduction Potential
Depending on the production pathway, using ammonia as a marine fuel can significantly reduce GHG emissions. The Well-to-Wake analysis reveals that ammonia-powered engines can reduce GHG emissions by up to 66% in the best-case scenario compared to ships operating on very low sulfur fuel oil (VLSFO).
For example, ammonia produced via electrolysis with renewable energy can reduce GHGs by up to 77% compared to traditional marine fuels. In comparison, ammonia from SMR with CCS achieves a more moderate reduction of around 50%. These figures are significant as the International Maritime Organization (IMO) has set ambitious targets to cut shipping emissions by at least 70% by 2040 and achieve net zero by 2050.
Challenges of Ammonia as Marine Fuel
While ammonia shows significant potential, it is not without challenges. One of the primary concerns is ammonia’s toxicity. It requires strict handling protocols to prevent leaks, which could harm human health and the environment. Moreover, ammonia combustion can lead to forming nitrogen oxides (NOx), which are harmful pollutants. Engine manufacturers are working on solutions to minimise these emissions, such as selective catalytic reduction (SCR) systems.
Another challenge lies in the supply chain. Ammonia is not yet widely available as a marine fuel, and current production facilities are not optimized for low-carbon ammonia production. Additionally, the infrastructure for ammonia bunkering and transport needs to be developed to make it a viable alternative on a global scale.
Planned Ammonia-Powered Ships
Ammonia presents a viable path toward decarbonizing the shipping industry. When produced through sustainable methods, it has significant GHG reduction potential. While there are currently no large ammonia-powered ships in commercial operation, several are planned.
Yara is developing an ammonia-powered container ship together with the North Sea Container Line, the Yara Eyde. The vessel will be used on a sea route between Norway and Germany. The ship is expected to start operations in 2026
Seaspan and the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping have developed a concept design for an ammonia-powered 15,000 TEU container vessel. The challenge is doing it in such a way that it is commercially feasible.
There is also an ammonia-powered tugboat nearing, which Amogy is building. The retrofitted ship, called the NH3 Kraken, is expected to be ready at the end of 2024.
Header image: yara.com
