Ammonia could become an important energy source in the future: as a CO2-free fuel in shipping, as hydrogen storage or as a source of electricity in fuel cells. If ammonia is produced from “green” hydrogen, it is also considered sustainable. But the supposedly “green” energy source also has a dark side, as a nitrogen expert now shows. The unregulated use of ammonia can release nitrogen oxides, nitrous oxide and other pollutants that harm the climate, the environment and people.
Ammonia (NH3) is considered a promising helper in the energy transition. This is because the combination of nitrogen and hydrogen does not release carbon dioxide when burned. It is therefore suitable as a fuel, but also as a chemical storage for green hydrogen. Unlike this, ammonia becomes liquid at minus 40 degrees or a pressure of nine bar and is therefore easier to handle than hydrogen. “Ammonia is almost as energetic as hydrogen and easy to liquefy,” explains Jan Willem Erisman from Leiden University. “On top of that, we already have more than a century of experience in production, storage and transport. This makes ammonia, for example, an attractive fuel for shipping and industry.”
Ammonia and the nitrogen cycle
But ammonia also has a dark side – the nitrogen compound is not as green and “clean” as it seems at first glance. This is proven by experience from agriculture, where ammonia has been used as a fertilizer ingredient for decades. “It is true that ammonia production using the Haber-Bosch process has enabled significant growth in agricultural yields and thus in the world population as well as in industrial products and ammunition,” writes Erisman. “But what originally emerged as a solution to nitrogen shortages has become a dominant driver of nitrogen excess, with far-reaching consequences for ecosystems, climate and human health,” said the researcher.
Negative consequences of ammonia production and its use, especially as fertilizer, have led, for example, to eutrophication of water bodies; in many intensively agricultural regions, too much nitrate ends up in the soil and groundwater. In addition, the greenhouse gas nitrous oxide (laughing gas) and nitrogen oxides are produced during ammonia degradation. “Together, such nitrogen losses contribute significantly to air pollution, eutrophication and soil acidification,” explains Erisman. Unfortunately, also biodiversity and, last but not least, human health.
Environmental guidelines are urgently needed
If ammonia is now produced and circulated in even larger quantities as fuel and hydrogen storage, these environmental problems could become even worse, warns the researcher. According to estimates by the International Energy Agency, global ammonia production could increase as transport decarbonizes. Electricity generation and industries will increase two to three times by 2050. “The current focus on ‘green ammonia’ reflects the trend to focus on decarbonization,” says Erisman. Such a focus on climate protection is also urgently needed. Nevertheless, he sees a danger in overlooking the negative consequences of ammonia use for the nitrogen cycle and the environment.
“My biggest concern is that nitrogen in the environment is not getting enough attention again,” says Erisman. Ammonia could play an important role in the energy transition as long as emissions and losses during use are kept under control. ‘We need political measures to prevent nitrogen emissions. We also need stricter rules to limit losses across the entire chain, from production and storage to transport and use.” Only then can CO2 emissions be reduced and new nitrogen problems avoided at the same time.
Source: Leiden University; Specialist article: One Earth, doi: 10.1016/j.oneear.2026.101621