Calling on Marine Engine Manufacturers for Transparency of Emissions Data

Making nitrous oxide and ammonia emissions data available is essential to assessing the climate impacts of ammonia as a shipping fuel.

April 11, 2024
Debora Schneider, (212) 616-1377

Today, Environmental Defense Fund and The Nature and Biodiversity Conservation Union, together with a group of other environmental nonprofit organizations, sent an open letter to global marine engine manufacturers calling for greater transparency on the emissions of nitrous oxide and ammonia from ammonia-powered engines.

"Complete and transparent information on emissions from ammonia-powered engines is critical to accounting for the full lifecycle emissions of ammonia, from its production to its end-use, and understanding its true climate impacts as a shipping fuel,” said Natacha Stamatiou, Senior Analyst, Global Shipping at Environmental Defense Fund. “Without this data, assessing the potential environmental implications of the fuel’s use will be largely based on assumptions which can limit the reliability of results."

As the shipping industry looks to accelerate its decarbonization to comply with the global temperature target of the Paris Agreement, stakeholders are looking for clean, alternative energy sources to fossil fuels. While ammonia is currently one of the most popular alternative fuel options on table, how its use as a shipping fuel will affect climate and the environment is still not fully understood. This is due in part to the lack of available emissions data from compatible engines.

“The climate crisis does not wait so we must hurry up with solutions. We have to make sure to take the right steps to protect the climate and the environment,” said Sönke Diesener, Transport Policy Officer at The Nature and Biodiversity Conservation Union. “It’s of outmost importance to have guaranteed transparency on the possible downsides to make sure we find the right technical solution and create a regulatory framework that minimizes the risks.”

Detailed empirical data on these types of emissions will enable industry executives and policymakers to devise better, more effective policies and solutions to tackle shipping’s climate impact. Engine manufacturers should provide clear evidence of nitrous oxide and ammonia emissions rates in grams per kilowatt hour or as a percentage of fuel consumption for a wide range of load points – from 5% to 90%. This additional information can mobilize the investment needed to scale alternative fuels and technologies for a just and equitable transition toward net zero, while supporting a thriving shipping industry.

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About Environmental Defense Fund:
One of the world’s leading international nonprofit organizations, Environmental Defense Fund ( creates transformational solutions to the most serious environmental problems. To do so, EDF links science, economics, law, and innovative private-sector partnerships. With more than 3 million members and activists and offices in the United States, China, Mexico, Indonesia and the European Union, EDF’s scientists, economists, attorneys and policy experts are working in 28 countries to turn our solutions into action. Connect with us on Twitter @EnvDefenseFund.

About NABU - The Nature and Biodiversity Conservation Union:
Founded in 1899, NABU (The Nature And Biodiversity Conservation Union, ) is Germany’s oldest and largest environmental association. With more than 940,000 members and 70,000 active volunteers, NABU works to protect species, habitats, and climate, at home and worldwide. Our projects around the globe empower strong local partners to take action for nature conservation and against the climate and biodiversity crises.