A First Approach to the Calculation of Nitrogen Footprint in Lisbon, Portugal

Abstract

Food and energy production have negative impacts due to the buildup of reactive nitrogen in the environment and subsequent nitrogen (N) impacts. To quantify the nitrogen footprint left in the environment by an individual, scientists from the University of Virginia USA developed a model to calculate nitrogen footprints, the N-Calculator, which transforms data on food and energy consumption into kg N per year lost into the environment. To calculate the average N footprint for an individual in the area of Lisbon, one thousand Lisbon inhabitants were surveyed at random using the N-Footprint questionnaire. The average N footprint estimated for Portugal was 25.5 kg N per capita per year and the average personal N footprint for the Lisbon area was 24.7 kg N per capita per year. The average N footprint for men and women was similar and, despite a tendency for people over the age of 65 to have a lower footprint, there was no statistical difference across the age groups studied (e.g., the N-Footprint for > 65 and 21–30 years of age was 23.5 and 25.8 kg N per capita per year, respectively). Losses of N to the environment were always higher for food consumption than for energy. Generally, the food types consumed do not comply with the recommendations of the Portuguese Association of Nutritionists for a healthy diet.