Running ships on ammonia will need new policies and technology

Ammonia, long seen as a viable, zero-carbon fuel for shipping, poses health risks that would need improved technologies and regulations to mitigate.

In 2022, the Global Maritime Forum announced that ‘There is no single fuel – no silver bullet – for future zero-carbon marine fuels, but there is increasing consensus that ammonia will have a key role to play.’

This week a new study – Climate and air quality impact of using ammonia as an alternative shipping fuel – suggests that under current legislation, switching the world’s ships to ammonia could cause up to about 600,000 additional premature deaths each year.

Shipping currently accounts for 3% of global CO2 emissions and, along with ammonia, a wide range of fuels such as LNG, LPG, methanol, biofuel and hydrogen have been suggested as clean alternatives.

The new research, from the Massachusetts Institute of Technology, looks at the impact of using pure ammonia, which generates nitrous oxide (N2O), nitrogen oxides (NO and NO2) while toxic, unburnt ammonia can also slip out.

However, the picture is not as gloomy as so far painted. The team believe that with tougher regulations and improved technology, the use of ammonia could save 66,000 lives compared to those lost under the status quo.

Anthony Wong, a postdoc in the MIT Center for Global Change Science and lead author of the study. said: ‘Not all climate solutions are created equal. There is almost always some price to pay. We have to take a more holistic approach and consider all the costs and benefits of different climate solutions, rather than just their potential to decarbonize.

‘In theory, if you are burning green ammonia in a ship engine, the carbon emissions are almost zero,’ Wong says, but adds the caveat: ‘Saying that ammonia is a ‘clean’ fuel is a bit of an overstretch. Just because it is carbon-free doesn’t necessarily mean it is clean and good for public health.’

Their research fixed on a number of scenarios involving two ship engines (one burning pure ammonia, the other ammonia mixed with hydrogen to improve combustion and optimise the performance of a catalytic converter) and three policy scenarios in which legislation restricts global emissions to varying degrees.

They found that in the worst-case scenario: no new regulations and ships running pure ammonia, switching the entire fleet would cause 681,000 additional premature deaths each year.

Wong put this into perspective: ‘While a scenario with no new regulations is not very realistic, it serves as a good warning of how dangerous ammonia emissions could be. And unlike NOx, ammonia emissions from shipping are currently unregulated.’

Running with the more efficient engine – even without new regulation – the number of premature deaths would be reduced to about 80,000, roughly 20,000 fewer than are currently blamed on shipping emissions. With regulations those 20,000 prevented deaths would rise to around 66,000.

Co-author Noelle Selin concluded: ‘The results of this study show the importance of developing policies alongside new technologies. There is a potential for ammonia in shipping to be beneficial for both climate and air quality, but that requires that regulations be designed to address the entire range of potential impacts, including both climate and air quality.’

The full study can be read here