Container ships, with their massive diesel engines, significantly contribute to global pollution, impacting climate and human health. Maritime shipping accounts for nearly 3% of global carbon dioxide emissions, with detrimental effects on air quality causing approximately 100,000 premature deaths annually.
Decarbonizing shipping is a primary goal of the International Maritime Organization (IMO), a U.N. agency that oversees maritime transport. Transitioning to sustainable fuels, such as ammonia, presents a potential solution. However, a recent study by an interdisciplinary team from MIT and other institutions warns that without strengthened emissions regulations, ammonia could exacerbate air quality issues and public health impacts.
Ammonia combustion generates nitrous oxide (N2O), a greenhouse gas about 300 times more potent than carbon dioxide. It also emits nitrogen oxides (NOx) and can release unburnt ammonia, forming fine particulate matter in the atmosphere. These pollutants are linked to severe health problems, including heart attacks, strokes, and asthma.
The study indicates that, under current regulations, switching to ammonia fuel could lead to up to 600,000 additional premature deaths annually. Conversely, with stronger regulations and cleaner engine technology, this switch could result in about 66,000 fewer premature deaths than current maritime emissions cause, significantly reducing global warming impacts.
The maritime industry’s reliance on ammonia hinges on technological advancements and regulatory frameworks. Researchers examined two types of ship engines: one burning pure ammonia, which emits higher levels of unburnt ammonia but fewer nitrogen oxides, and another mixing ammonia with hydrogen, improving combustion and catalytic converter performance.
Three policy scenarios were evaluated: current regulations limiting NOx emissions in select regions, expanded ammonia emission limits over North America and Western Europe, and global limits on ammonia and NOx emissions. The findings underscore the necessity of integrating new regulations with technological innovations to mitigate ammonia’s potential health risks.
A significant challenge in this study was the lack of real-world data, as ammonia-powered ships are not yet operational. Researchers utilized experimental ammonia combustion data to model potential outcomes. The study reveals that without new regulations, burning pure ammonia could cause 681,000 additional premature deaths annually. Cleaner engine technology alone could reduce this number to about 80,000 premature deaths, and with stronger global regulations, deaths could be reduced by approximately 66,000.
The impact of ammonia emissions would vary globally, with East Asia experiencing the highest premature death rates due to less stringent air quality regulations and higher existing pollution levels. Effective global strategies are essential to address these disparities and ensure uniform benefits from transitioning to ammonia fuel.
