Green Ammonia – the Key to Decarbonizing Shipping?

in Decarbonization, Trends by

There’s no doubting the magnitude of the problem. And the urgent need to tackle it. Maritime shipping accounts for nearly 3% of the world’s annual CO2 emissions, says the IMO. In 2018, IMO delegates agreed to cut emissions by 50% from 2008 levels by 2050. But with less than three decades to go, the target seems more unattainable than ever. Developing viable alternatives to diesel fuel is a more time-critical challenge than ever before. Can green ammonia solve shipping’s carbon crisis?

What is Green Ammonia?

In the context of the greening of ammonia, it is important to remember just how dependent the world already is on the conventional product. Half our global food production depends on ammonia as a key component of mineral fertilizer. Production of this pungent, colourless gas – a simple molecule composed of three hydrogen atoms bonded to a single nitrogen atom – accounts for about 5% of the world’s gas consumption. That’s because ammonia (NH3) is conventionally made by means of the energy-intensive Haber-Bosch steam methane reforming process, which involves reacting hydrogen and nitrogen with a catalyst at high temperature (around 500° C.) and high pressure (20-40 mPa). Natural gas powers this process. Hence, the equation for green ammonia involves replacing this fossil fuel with renewable energy. Green hydrogen is produced by splitting water into hydrogen and oxygen by means of electrolysis, while the nitrogen required for ammonia synthesis is produced by air separation technology. Often referred to as “Power-to-X”, manufacturing green ammonia is not such a complex process; it just requires vast amounts of green energy.

Green Ammonia as a Fuel

Although green ammonia has nine times the energy density of Li-ion batteries and three times that of compressed hydrogen, there are significant hurdles to its use in maritime shipping – primarily its expense, the lack of production facilities, and its toxicity. A poll at the Ammonia Energy Conference in November 2020 revealed that 35% of respondents saw the greatest barrier to green ammonia as a shipping fuel was the lack of a carbon tax, 32% thought it was the cost of green hydrogen production. Here, the way ahead has to come from the introduction of taxation on carbon emissions and more punitive legislation. Demands for a carbon tax have been heard for years but, as yet, little progress has been made as the regulatory framework is largely missing. Even if the price of green ammonia were to fall, the current lack of large-scale production facilities is a huge challenge to ammonia-powered shipping. Last but not least, using ammonia to power a vessel brings new risks. Ammonia is corrosive to some alloys containing copper and nickel as well as to some plastics. It is difficult to ignite, does not maintain combustion well, and when burned at high temperatures, produces nitrogen dioxide, which is harmful to respiratory systems, as well as small amounts of nitrous oxide, a highly potent greenhouse gas. In other words, the path to this carbon-free fuel is far from smooth.

The risks are obvious and there have been several maritime accidents with ammonia involved. Visit the Maritime News section of to find a list of recent incidents.

Signs of Progress

One means of eliminating harmful emissions is to use fuel cells to power a ship. Multiple projects have demonstrated that proton-exchange membrane fuel cells can propel smaller vessels (e.g. ferries and submarines), but ammonia is not as suitable a fuel as hydrogen for these fuel cells. However, solid-oxide fuel cells may prove a better fit. A 2-megawatt system using this technology has been installed in the Viking Energy supply ship in Norway and will be tested from 2024 onwards. Wärtsilä has begun testing ammonia in a marine combustion engine in Stord, Norway. MAN Energy Solutions and Samsung Heavy Industries are collaborating to develop the first ammonia-powered oil tanker by 2024.

On the production front, things are also moving forward, albeit very slowly. Worldwide, only tiny amounts of green ammonia are currently produced. Trial plants in Japan and the UK produce a mere 30-50 kg a day, though larger initiatives have been launched in Australia, Denmark, Chile, New Zealand, and Saudi Arabia. In Queensland, a feasibility project for a plant that could produce 20,000 metric tons a year using 208 GWh of green electricity has received state backing. But to put that figure in perspective, the global shipping industry consumed the equivalent of 3.05 million GWh in 2015. Replacing just 10% of that total with green ammonia would require some 550,000 GWh of renewable energy.

In July 2020, it was announced that a $5bn green ammonia plant would be constructed in northwest Saudi Arabia to produce 1.2 million metric tons a year. In another small step forward in Western Jutland, Denmark, the wind energy giant Vestas is backing the development of a 10 MW commercial-scale green ammonia plant that could be operating by 2022. 

Although conventional ammonia is currently stored and handled in 120 ports around the world and these facilities could easily be switched to the green variety, there is still a long way to go before green ammonia becomes viable for maritime shipping. But as a carbon-free fuel, it is believed to have a viable future in maritime shipping. A report published in September 2019 by DNV predicted that ammonia could account for 25% of maritime fuel by 2050, while all newly built ships may well be running on ammonia from 2044. Two industry experts are also optimistic. Morten Bo Christiansen, Vice-President and Head of Decarbonisation at A.P. Möller – Maersk: “Alongside methanol … we see green ammonia as an important future fuel …”. Peter Kirkeby of MAN Energy Solutions: “On the technology side, we see some work ahead for ammonia. But it’s doable.”

Read a guest article on scenarios for a supply and demand network for Green Ammonia provided by Professor René Bañares-Alcántara of the University of Oxford. FleetMon provided certain AIS data to support this project on decarbonizing crucial shipping routes. Reach out to us if you need AIS data for academic purposes.