Representational image of a tanker ship.
Ammonia (NH3) is a chemical compound based on hydrogen and nitrogen that can be commonly found in nature.
Required for different biological processes, ammonia is an essential precursor in synthesizing amino acids — the basic units of proteins — and nucleotides — the fundamental building blocks of nucleic acids (DNA and RNA) — in living organisms. In the environment, ammonia is produced in the nitrogen cycle through various bacterial processes in the soil.
Apart from its role in the ecosystem, ammonia is widely utilized as a fertilizer for enriching soil quality and stimulating plant growth through its concentrated nitrogen content.
Additionally, it is used to produce industrial chemicals that find their purpose in many industries, including pharmaceuticals, textiles, explosives, cleaning products, and plastics.
Lately, ammonia has emerged as a prospective fuel alternative for the shipping industry, which according to the International Maritime Organization (IMO), needs to hit net-zero greenhouse gas emissions by 2050.
This is in response to the fact that 90 percent of the world’s physical goods trade is carried out by ships burning heavy fuel oil, and emitting harmful pollutants. These emissions contribute to nearly three percent of all global greenhouse gas emissions.
But, since its manufacturing process (Haber-Bosch) relies on fossil fuels for hydrogen and energy, ammonia production stands out as one of the leading industrial contributors to carbon dioxide (CO2) emissions. Each metric ton of ammonia currently adds about 1.9 metric tons of greenhouse emissions to the atmosphere.
Scientists believe that green ammonia, a carbon-free form produced using renewable energy sources such as wind or solar power, can be a viable fuel solution to meet IMO’s targets.
According to a recent study published in the open-access journal Environmental Research: Infrastructure and Sustainability, offering it at just 100 fuel ports could even help decarbonize 60 percent of global shipping.
René Bañares-Alcántara, PhD, a co-author of the study and professor of chemical engineering at the Department of Engineering Science at the University of Oxford, highlights green ammonia as the optimal choice for the future of shipping.
“Ammonia (green or otherwise) can be combusted, used in fuel cells, or decomposed back into hydrogen,” Bañares-Alcántara told IE in an interview. It is less energy-dense than fossil fuels but does not generate CO2 emissions when used. The difference in energy content is important but not dramatically lower.”
“Other alternatives, e.g. bio-fuels, green methanol, hydrogen, blue fuels, etc., either have limited future availability, higher costs or generate CO2 emissions when used,” Bañares-Alcántara said.
However, based on the research, making the transition would incur a significant cost of USD 2 trillion in developing the infrastructure for a fuel supply chain. “Green ammonia is currently more expensive than very low sulfur (fossil) fuels, however with the steep reduction in the cost of renewable energy and the very likely increase in carbon taxes, costs will likely be equivalent in 2030-2035, and predictions indicate that green ammonia will be cheaper than fossil fuels by 2040-2050,” the professor emphasizes.
According to the study, Australia has the greatest investment need, with large production clusters predicted in Chile, California, North-West Africa, and the southern Arabian Peninsula.
In addition to the substantial investment required for switching to ammonia, Bañares-Alcántara, whose research group OXGATE develops techno-economic models of green ammonia and green hydrogen to determine where and how they can be produced at minimal cost, points out another obstacle – its toxicity.
“It is something to consider seriously, but ammonia is already the second most produced chemical in the world (given its use for fertilizers), and so around 180 million tons of ammonia is being produced globally, and a substantial amount is moved from producing plants to where it is consumed,” explained Bañares-Alcántara. “In short, industry and governments know how to deal with ammonia as a chemical.”
Bañares-Alcántara suggests that providing green ammonia at only ten regional ports across ten different areas or at 100 ports globally could meet over 60 percent of the global shipping fuel needs.
“This is still a small number of ports that would have to be converted to green ammonia given that we are considering 1,360 ports globally,” the scientist said. “The estimation comes from an optimization where ports are ranked in terms of their fuel consumption and the largest fuel consumption ports are converted in ranking order. The effect is incremental.”
However, due to the reduced energy density of green ammonia, ships may need to adopt slower speeds to reduce drag force, allocate more space for fuel tanks (thus reducing cargo capacity), or make more frequent stops for refueling, resulting in longer arrival times.
“Fortunately, none of these effects are dramatic or insurmountable, and they would only increase the cost of transportation by a very small fraction,” said Bañares-Alcántara. “Shipping is one of the most challenging sectors to decarbonize because of the need for fuel with high energy density and the difficulty of coordinating different groups to produce, utilize, and finance alternative (green) fuel supplies.”
To guide investors, the team developed a modeling framework that crafts feasible scenarios for establishing a worldwide supply chain for green ammonia fuel.
The framework integrates a fuel demand model, potential trade scenarios, and a spatial optimization model for green ammonia production, storage, and transportation. It aims to identify optimal locations for meeting future shipping fuel demand.
“The implications of this work are striking,” said Bañares-Alcántara. “Under the proposed model, current dependence upon oil-producing nations would be replaced by a more regionalized industry; green ammonia will be produced near the equator in countries with abundant land and high solar potential, and then transported to regional centers of shipping fuel demand.”
However, researchers from Chalmers University of Technology in Sweden warned about the risks of utilizing ammonia as a marine fuel.
Their study, published in the peer-reviewed journal Applied Energy, cautioned that eutrophication and acidification are just some environmental problems associated with using ammonia. Additionally, it notes nitrous oxide emissions, a potent greenhouse gas, as another concern.
“Although ammonia is carbon-free, its combustion in engines is not free from greenhouse gas emissions”, said Selma Brynolf, PhD, maritime technology researcher and co-author of the paper. “Engine tests have shown varying degrees of emissions of laughing gas, which is a very potent greenhouse gas with more than 200 times the global warming impact than carbon dioxide.”
“There is simply a lack of deeper risk analyses of what a switch to ammonia could mean”, said Fayas Malik Kanchiralla, PhD student at the Department of Mechanics and Maritime Sciences at Chalmers and lead author of the paper.
“To sum up; even though green ammonia is a fossil-free and relatively clean fuel, it is probably not green enough for the environment as a whole,” concluded Kanchiralla. “More risk assessments on the emissions of ammonia, and the related nitrogen compounds, need to be done before adopting this fuel for shipping.”
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Georgina Jedikovska Georgina Jedikovska, journalist, plant engineer, oenophile and foodie. Based in Skopje, North Macedonia. Holds an MSc. degree in Horticultural Engineering, with a specialization in viticulture and oenology. Loves travelling, exploring new cultures, a good read, great food and flavorful wines. Enjoys writing about archaeology, history, and environmental sciences.
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