The US nitrogen footprint: An updated approach and comparison

Over a dozen countries have calculated their per capita nitrogen footprint, but the assumptions and system bounds sometimes vary. In this paper, we propose a more detailed and improved per capita nitrogen footprint methodology to help ensure comparability and consistency in nitrogen footprint calculations and system bounds. We present a case study for the United States. The focus of the update was the virtual nitrogen factors, which describe nitrogen losses during the food production process. We then compare the US nitrogen footprint to other countries, both in terms of the results and the comparability of approaches.

The nitrogen footprint approach has been applied in over a dozen countries, including the US, the Netherlands, the United Kingdom (Stevens et al. 20, Germany, Austria, Australia, Japan, China, Tanzania, and more (Galloway et al. 2014). Calculations are in-progress in Brazil, Denmark, Portugal, and Ukraine. Although these calculations often include the major components to a per capita nitrogen footrint, the approaches and system bounds sometimes vary. In this paper, we present an updated and more detailed methodology for calculating a national-scale per capita nitrogen footprint. We present a case study for the US.