Nitrogen (N) is crucially important to living things as an essential component to form proteins and DNAs. Earth’s atmosphere is composed of 78% molecular nitrogen (dinitrogen, N₂), N is everywhere as N₂. However, N₂ is inert and most of living things cannot utilize it directly. What is needed is reactive nitrogen (Nr, N compounds other than N₂). Our eating is a way to intake N as proteins. We need Nr as fertilizers to produce sufficient food from limited areas of agricultural lands. The Haber–Bosch process, an artificial N fixation technology, developed in the early 20th century enables to create Nr from N₂ as desired. The fixed Nr has provided great benefits to us as chemical fertilizers and industrial materials. In recent years, a new N use as fuels is also emerging.

On the other hand, much of Nr we use leaks into the environment. The low N use efficiency (NUE, here the ratio of N in products to the total N input) in our food system is the biggest cause. In addition to the low NUE in food production, consumption aspects such as the preference for livestock products with relatively low NUE and the loss of edible food also lower the whole system NUE. Fossil fuel combustion for energy conversion and waste incineration are also sources of Nr emissions. The environmental Nr loss causes various N pollution such as climate change, stratospheric ozone depletion, air pollution, water pollution, eutrophication, and acidification that threats human and ecosystem health. This trade-off, N use to earn benefits is accompanied by N pollution with threats, is called the N issue (Figure below). We owe the current Earth to future generations. This research is conducted to obtain integrated knowledge that will address the N issue and realize sustainable N use so that we and future generations can live with happiness.

Our N use (benefits) causes N pollution (threats)

Sustai-N-able Project aims for three breakthroughs.

To achieve the three breakthroughs, members from a wide range of fields, including researchers in natural, social, and cultural sciences and experts in food culture, gather to tackle the following: elucidating the natural N cycle and ecosystem responses, elucidating N cycle in human society, building future N use scenarios, measuring the social N cost, evaluating the cost and benefit of the N issue, creating various educational opportunities on the N issue, and implementing the Future Design of sustainable N use.

As domestic activities, we establish several research sites, as well as collaborate with related programs and projects and local governments, agencies, and ministries in addition to nationwide analyses. As international activities, we collaborate with the International Nitrogen Initiative, the United Nations Environment Programme, the Task Force on Reactive Nitrogen/Convention on Long-range Transboundary Air Pollution, and others.

Sustai-N-able project consists of four Research Units: Natural Cycling, Human Society, Economic Evaluation, and Future Planning. The first three units are responsible for interdisciplinary research, and the last unit is responsible for transdisciplinary research with various stakeholders while integrating the scientific knowledge collaborating with the other three units. The main tasks for each unit are shown below.