Clean ammonia as shipping fuel: the good, the bad, the ugly - and the numbers

Navigating clean ammonia as the future fuel for shipping: as the maritime industry charts its course towards a sustainable future, clean ammonia emerges as a promising solution to decarbonise the world's shipping fleet.

Clean ammonia could decarbonise 60% of global shipping.

In this voyage, there are nuances to consider—the good, the bad, the ugly—and the numbers that underline the potential impact. This "long read" sets sail to explore ammonia as a shipping fuel and examine the challenges and opportunities that come with clean innovation.

The current globalised economy demands a massive fleet of ships, cutting through the oceans while transporting goods over vast distances. This demand results in 3% of the world's greenhouse gas emissions (845 MtCO2eq in 2023) and polluting aerosols that acidify the oceans.

Decarbonising the shipping business is paramount to climate mitigation strategies. The International Maritime Organisation has pledged to reduce emissions by 40% by 2030 and attain Net Zero by 2050. Because of the sector's specifics, decarbonising how we power this fleet is one of the most complex challenges of the energy transition.

Although efficiency increases and optimisation can partly achieve that goal, switching to low- or zero-carbon fuels has the greatest potential for significant reductions.

Decarbonising shipping

Ship design maximises cargo space and has to limit the space destined to carry fuel to achieve profitability. Therefore, fuels need enough energy density (how much energy they store for a given volume) to make operations economically feasible. Safe measures for storage also have to be in place. Ships last many years (around 20 years) and cannot be replaced in an instant. While retrofits are being considered, they can cost more than building a new ship.

The main bets to replace fossil fuels are e-methanol, biofuels, electrification, hydrogen and clean ammonia. Each of these has its advantages and disadvantages. Still, because of its higher energy density than hydrogen, the experience handling it in other contexts such as for fertiliser, the existing infrastructure, and the fact that it is near carbon-zero, clean ammonia has emerged as the frontrunner in terms of long-term potential.

Emissions reductions potential

Well-to-wake GHG emissions for clean ammonia are estimated to be at least 85% less than those of conventional marine fuel.

Shipping activity is forecasted to increase from 125 trillion tonnes per km to 145 in 2030 and 265 in 2050. With no substantial changes to energy sources, yearly emissions rise accordingly. In the IEA's Net Zero scenario, emissions in 2050 fall by 90% compared to the Stated Policies Scenario, and ammonia is the primary low-emissions fuel used to decarbonise shipping.

The impact of emissions reductions could reach a whopping 986MtCO2/year by 2050.

Environmental co-benefits

Mitigating climate change is just one benefit of replacing fossil marine fuels.

Half the world's fleet depends on heavy fuel oil (HFO), literally 'the bottom of the barrel'. Besides the CO2 emissions, burning these fuels emits aerosols like 22Mt of NOx, 11 Mt of SOx and 3Mt of particulate matter, which pollute the atmosphere, cause climate change and acidify the oceans. Sulphate aerosols also have a cooling effect that masks global warming.

Moreover, it emits black carbon, a polluting particle with a high global warming potential (GWP) of 900, which represents 6% of carbon dioxide equivalent emissions and severely impacts the Arctic, where it accumulates in the lower atmosphere, absorbing heat, supercharging climate change and disrupting ecosystems.

Replacing bunker oil with clean ammonia prevents carbon dioxide emissions and most other pollutants.

Clean ammonia as shipping fuel

Clean ammonia can be used for marine propulsion in internal combustion engines or fuel cells (as ammonia or hydrogen after decomposition).

Ammonia combustion technologies available today result in emissions of nitrogen oxides, including N2O, a potent greenhouse gas causing climate change and the most significant contributor to ozone depletion today.

Ammonia is an aerosol precursor, so leaks or emissions from incomplete combustion also impact aerosol loading and ozone depletion. It could also contribute to acid deposition and eutrophication, disturbing biogeochemical flows.

Fuel cells are primarily emissions-free, but nitrous oxides, such as NO and NOx, could be formed at high temperatures, impacting climate change and ozone depletion. However, to capture NOx emissions, you can also use ammonia. There are also CO2 emissions associated with their production and life cycle.

Clean ammonia production: avoiding environmental problem shifting

Generating renewable energy for hydrogen production requires land and water, depending on the technology - bioenergy is incredibly demanding. Extracting materials to produce solar panels or wind turbines degrades ecosystems and harms biodiversity. Deployment of these technologies can put pressure on wildlife. Producing hydrogen from electrolysis also demands water.

The choice of technology and site, proper environmental impact studies, careful selection of renewable energy and hydrogen partnerships, and having a local communities-centric view when developing projects are all essential to ensure that clean ammonia gets produced without shifting the burden to other planetary systems that sustain life.

Fortunately, ammonia is one of the most traded commodities in the world, and the technical know-how and regulatory framework of an ammonia economy are mature — but not as fuel, where other concerns need addressing for deployment.

A risky and toxic substance

Though its flammability is no longer more of a problem than current fuels, ammonia is toxic. Even small concentrations can irritate the eyes, throat and breathing pathways and can be lethal in higher concentrations. In an enclosed vessel, this represents a serious safety hazard, as do the explosion risks if containers are exposed to heat.

Despite the maturity of the supply chain, the introduction of ammonia as shipping fuel would likely increase accidents. Spills would have other risks, such as explosion, fire, or formation of a heavy, toxic gas cloud, which would be complex to dissipate and handle on a vessel at sea.

Moreover, in spills or accidents, its toxicity also affects sea life and ecosystems: ammonia dissolves in water to form ammonium hydroxide, which is highly toxic to marine life. Long-term consequences would cause nutrient imbalance, impacting the biogeochemical flow boundary, for example, with eutrophication.

Safety measures

In a recent European Maritime Safety Agency assessment, ammonia was considered suitable as a marine fuel because health, safety, and environmental risks are manageable. However, as with its chemical industrial application, this requires rigorous safety measures.

These will include adaptation to ship designs and additional concepts in ship designs such as the ammonia fuel containment system, bunker station, transfer piping, double-wall barriers and ammonia catch systems, as well as toxicity-zone requirements, gas-detection equipment, respiratory and eye protection, decontamination showers. Very detailed training requirements will need to be in place for safe operation, specific regulations will need to be developed, and specific HAZID studies will have to be conducted to identify preventive and mitigative safeguards for different ship types.

A glimpse at the numbers

Achieving the IMO goals of 5-10% uptake in zero of near-zero GHG emissions fuels by 2030 will require clean energy at the order of 0.6-12EJ. If 25% of that were supplied by ammonia, it would mean 8- 16 MtNH3. Some estimates of technology uptake place demand much higher, amounting to 295-670MtNH3 by 2050.

Almost 50% of the overall order book capacity is now alternative-fuelled, including 191 ammonia-ready ships. In the next ten years, $1.6 trillion of new-build orders are expected. The shipping industry 'clearly' intends to switch to clean fuels, especially ammonia.

The shipping industry and the environment

The oceans are essential to our biosphere and vital in sustaining life. Ships cause other issues in marine environments, such as ship strikes injuring sea life; oil spills, wastewater discharges and untreated ballast water, which is associated with the introduction of invasive species; as well as underwater noise, plastic pollution, artificial lights, erosion and resuspension, all of which impact biodiversity and ecosystems.

Freshwater use in canals to allow navigation can severely impact local resources. Discharging of ship wastewater can increase nutrient contamination in the oceans, causing eutrophication, when excess nutrients make algae and plants grow so much that light stops reaching the depths and consuming the oxygen sea life needs to survive.

Sustainable shipping is also less shipping.

Ultimately, the most efficient way of reducing emissions and impacts from shipping is by reducing shipping demand.

Here, it is worth underlining a vital point: Since about 40% of shipping cargo is oil, coal, and gas, eliminating fossil fuels will eliminate much of the necessity for this marine traffic. But not all of it - green fuels (like hydrogen) will also need transporting. And there's still the 60% of remaining goods - with all the environmental impacts that come with them.

Nium can help accelerate the shipping industry's decarbonisation by providing the sustainable fuel currently the best bet to power shipping: clean ammonia.

But the way we do it, on-demand, is equally essential to a sustainable shipping transition: by also acting in the fertiliser market, supplying decentralised ammonia production for fertiliser, we help align the food systems with a decentralised, democratised paradigm that favours local production.

Ammonia as a fossil fuel alternative in shipping will require significant economical and safety derisking. But clean ammonia gives us an option worth investigating as a way of making a dent into 3% of total global emissions. By looking carefully at safety, environmental impact, and the necessary regulations, we can see a way forward to a future of carbonless shipping fuel.