As the global shipping industry seeks to reduce its carbon footprint, the potential shift from traditional diesel engines to ammonia fuel has garnered significant attention. A recent study led by researchers from the Massachusetts Institute of Technology raises critical concerns about this transition. While ammonia is touted as a nearly carbon-free alternative, the study indicates that without stringent emissions regulations, its combustion could lead to severe air quality issues and increased health risks, particularly in regions with less robust regulations.
The maritime shipping sector is responsible for approximately 3% of global carbon dioxide emissions and contributes to around 100,000 premature deaths annually due to air pollution. The International Maritime Organization, a United Nations agency, aims to decarbonize shipping by promoting sustainable fuels like ammonia. This shift could theoretically reduce carbon emissions significantly, especially if the ammonia is produced using renewable energy sources, a process referred to as "green ammonia." However, the combustion of ammonia also generates nitrous oxide potent greenhouse gas, and nitrogen oxides, which can have detrimental effects on air quality.
The study highlights alarming projections: under current legislative frameworks, transitioning to ammonia fuel could result in an additional 681,000 premature deaths each year. The researchers emphasize that ammonia combustion can release unburnt ammonia into the atmosphere, which contributes to the formation of fine particulate matter, tiny particles that can penetrate deep into the lungs and cause serious health issues such as heart disease, strokes, and respiratory ailments. Anthony Wong, a postdoc at MIT and lead author of the study, stresses the importance of adopting a holistic approach to climate solutions, considering all potential costs and benefits rather than focusing solely on carbon reduction.
To better understand the implications of ammonia use in shipping, the researchers developed a comprehensive model that assessed various scenarios based on different engine technologies and policy frameworks. They examined two types of ship engines: one that burns pure ammonia, which leads to higher emissions of unburnt ammonia, and another that mixes ammonia with hydrogen to optimize combustion and reduce emissions. The study also considered three regulatory scenarios, ranging from current regulations that only limit NOx emissions in certain regions to more stringent global limits on both ammonia and NOx emissions.
The findings reveal a stark contrast in potential outcomes based on regulatory approaches. Without new regulations, the switch to ammonia could exacerbate public health crises, particularly in East Asia, where shipping volumes are high and air quality regulations are lax. However, if cleaner engine technologies are adopted alongside stricter regulations, the number of premature deaths could be reduced by about 66,000, highlighting the critical need for integrated policy development in tandem with technological advancements.
Wong and his co-authors, including Noelle Selin, a professor at MIT, and Sebastian Eastham, now a senior lecturer at Imperial College London, emphasize that ammonia should not be considered a "clean" fuel without acknowledging its broader environmental impacts. The study serves as a cautionary tale, urging the maritime industry and policymakers to work collaboratively to address the full spectrum of emissions associated with ammonia fuel.
The research, funded by the MIT Climate and Sustainability Consortium, underscores the urgency of updating shipping emissions regulations to mitigate the potential health risks posed by ammonia combustion. As the industry moves forward, the findings aim to inform future discussions about sustainable shipping practices and the importance of comprehensive regulatory frameworks that consider both climate and air quality impacts.
