Nitrogen provides great benefits to humankind as a fertilizer, industrial material and fuel. However, our use of nitrogen unintentionally causes nitrogen pollution and threatens the health of humans and nature. In this project, we will elucidate the dynamics of nitrogen, of which much remains unknown; quantify the environmental burden and impact of nitrogen use; evaluate its benefits and threats and the effects of countermeasures and behavior change; and design the future to realize sustainable nitrogen use.

Nitrogen is an essential element for creating proteins, nucleobases, and other biomolecules. Although nitrogen is ubiquitous, with 78% of the earth’s atmosphere being nitrogen gas (N₂), most living organisms, including humans, do not have access to stable N₂ and require a form of nitrogen other than N₂ (reactive nitrogen, Nr). Our diet is also a means of obtaining nitrogen in the form of protein. To get more food from limited land, we need Nr as fertilizer, and ammonia synthesis technology (Haber-Bosch process), developed in the early 20th century, made it possible to obtain as much Nr as desired.

Synthesized Nr has been used as an industrial raw material as well as a fertilizer, providing a great benefit to mankind. On the other hand, much of the Nr used by humans is discharged into the environment along with its reactive properties. This is especially due to the low nitrogen use efficiency (NUE) of the food system. In addition to the low NUE of food production, there are consumption challenges such as food loss and a preference for livestock products with relatively low NUE. Combustion of fossil fuels and others is another source of Nr emissions.

As a result of Nr emissions into the environment, various forms of nitrogen pollution such as global warming, stratospheric ozone depletion, air pollution, water pollution, eutrophication, and acidification have occurred, causing damage to human and natural health. The trade-off between the benefits of nitrogen use with the threat of nitrogen pollution is called the “nitrogen issue” (Figure 1). To ensure that our future possibilities are sound, we conduct this research to gain integrated knowledge that will lead to solutions to the nitrogen issue and sustainable nitrogen use for future generations.

What we know so far

This research aims to achieve three breakthroughs in solving the nitrogen issue: first, the development of tools to enable quantitative analysis of the causal relationship between nitrogen use and nitrogen pollution; second, the spread of awareness of the nitrogen issue, which is not as well-known as other global environmental problems; and third, the implementation of future design to achieve sustainable nitrogen use. In the pre-research in FY2022, we established a research system to achieve these breakthroughs. In FY2022, we established three research groups: the Natural Circulation Group, the Human Society Group, and the Economic Evaluation Group, which are responsible for interdisciplinary research, and the Future Design Group, which is responsible for transdisciplinary research to achieve breakthroughs in collaboration with the three groups.

Noteworthy items

We have produced a project leaflet (in Japanese and English) that can be used to provide an overview of the nitrogen issue to various stakeholders and can be used as a catalyst for free discussion. The leaflets can be downloaded from the project website. In addition, a number of study sessions on the nitrogen issue were held at relevant ministries, agencies, and schools. The project leader was appointed as the representative of the East Asia Regional Centre of the International Nitrogen Initiative (INI), a group of experts, in November 2022.