Study Finds Ammonia As Marine Fuel Poses Risk To Public Health

5th August 2024

Carbon-free ammonia has been touted as the future of green shipping fuel, with orders already placed for the first ammonia-powered dual-fuel vessels. However, a new study from the Massachusetts Institute of Technology (MIT) reveals that burning ammonia could worsen air quality and lead to hundreds of thousands of premature deaths annually.

The study warns that, under current legislation, switching ships to ammonia fuel could result in approximately 600,000 additional premature deaths each year. The maritime industry, which currently accounts for nearly 3% of global CO₂ emissions, already causes about 100,000 premature deaths annually due to its negative impact on air quality.

MIT's research suggests that, with stronger regulations and cleaner engine technology, switching to ammonia could potentially reduce premature deaths by about 66,000 compared to current maritime emissions, while also lessening the impact on global warming.

Ammonia combustion produces nitrous oxide (N₂O), a greenhouse gas 300 times more potent than CO₂, and nitrogen oxides (NO and NO₂, known as NOx). Unburnt ammonia may also escape, forming fine particulate matter in the atmosphere. These particles can be inhaled deeply into the lungs, causing severe health issues such as heart attacks, strokes, and asthma.

Ammonia is traditionally produced by extracting hydrogen from natural gas and combining it with nitrogen at high temperatures, a process with a significant carbon footprint. The maritime industry is looking towards "green ammonia," made using renewable energy to produce hydrogen via electrolysis and generate heat.

However, even green ammonia generates N₂O and NOx when burned, with some unburnt ammonia escaping. This nitrous oxide remains in the atmosphere for over a century, while nitrogen emissions can damage ecosystems. Bacterial digestion of these emissions further produces N₂O. NOx and ammonia also mix with other atmospheric gases to form fine particulate matter, a primary air pollution contributor that causes an estimated 4 million deaths annually.

A significant challenge in assessing ammonia's impact is the lack of real-world data, as no ammonia-powered ships are currently in operation. Researchers relied on experimental ammonia combustion data from collaborators to build their models.

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