Nitrogen in the food system

Summary

Nitrogen (N) plays a dual role in the agri-food system: it is an essential nutrient for all life forms, yet also an environmental pollutant causing a range of environmental and human health impacts. As the plant nutrient needed in greatest quantities, and as a building block of proteins and other biomolecules, N is a necessary part of all life. In the last century, an enormous increase of N turnover in the agri-food system has enabled increasing per-capita food supply for a growing world population, but as an unintended side effect, N pollution has increased to levels widely agreed in science and policy to be far beyond sustainable limits. There is no such thing as perfectly circular N supply. Losses of N to the environment inevitably arise as N is transformed and used in the food system,