A nitrogen footprint model to help consumers understand their role in nitrogen losses to the environment

The human use of reactive nitrogen (Nr) in the environment has profound beneficial and detrimental impacts on all people. Its beneficial impacts result from food production and industrial application. The detrimental impacts occur because most of the Nr used in food production and the entire amount of Nr formed during fossil fuel combustion are lost to the environment where it causes a cascade of environmental changes that negatively impact both people and ecosystems. We developed a tool called N-Calculator, a nitrogen footprint model that provides information on how individual and collective action can result in the loss of Nr to the environment. The N-Calculator focuses on food and energy consumption, using average per capita data for a country. When an individual uses the N-Calculator, the country average is scaled based on the individual's answers to questions about resource consumption. N footprints were calculated for the United States and the Netherlands, which were found to be 41 kg N/capita/yr and 24 kg N/capita/yr, respectively. For both countries, the food portion of the footprint is the largest, and the food production N footprints are greater than the food consumption N footprints. The overarching message from the N-Calculator is that our lifestyle choices, and especially our food consumption, have major impacts on the Nr losses to the environment. Communicating this message to all of the stakeholders (the public, policymakers, and governments) through tools like the N-Calculator will help reduce Nr losses to the environment.