The Integrated Nitrogen Footprint Project

The human use of reactive nitrogen in the environment has profound beneficial and detrimental impacts on all people. Agricultural uses, including food production and consumption, contribute the most reactive nitrogen to the environment. The main beneficial impact of the agricultural use of reactive nitrogen is the food produced by nitrogen fertilizer and human-enhanced biological nitrogen fixation. But, detrimentally, most of the N used in food production and all of the N used in energy production are lost to the environment. Of the N used to produce food, about 80% is lost before consumption, and the remainder is lost after consumption.

Once lost to the environment, this nitrogen moves through the Earth's atmosphere, forests, grasslands and waters causing a cascade of environmental changes that negatively impact both people and ecosystems. These changes include smog, acid rain, forest dieback, coastal ‘dead zones’, biodiversity loss, stratospheric ozone depletion and an enhanced greenhouse effect.

Responding to the challenge in communicating to the public the complexities of nitrogen's interactions with the environment, UVA Food Collaborative members Professor James Galloway and Research associate Allison Leach of the Department of Environmental Science, along with a team including Albert Bleeker and Jan Willem Erisman (Energy Research Center of the Netherlands) and Rick Kohn (University of Maryland), are building an innovative model for calculating one's nitrogen footprint. The Integrated Nitrogen Footprint Project's “N-Calculator’, is a tool that allows individuals to calculate their nitrogen footprint. The tool in its current form can also be scaled for use by communities, organizations, or even countries.

To calculate your own nitrogen footprint, please visit this website: www.N-Print.org.

When using the N-Calculator, a user is asked questions about resource consumption in the following areas:

  • Food consumption
  • Housing
  • Transportation
  • Goods and services

The N-Calculator, which starts with the average per capita consumption and footprint in a country, is then scaled based on the user's answers. The calculator estimates the nitrogen lost per unit of resource consumption.

As of May 2010, Galloway, Leach, and their team are near completion of the construction of the N-Calculator for the US and the Netherlands (NL). The beta version of N-Calculator found that the average per-capita N footprint in the United States (Figure 2a) is greater than that of the Netherlands (Figure 2b), at 38 kg N/capita/yr and 27 kg N/capita/yr, respectively.


2a

2b

Figure 2: The average per-capita Nitrogen Footprint for the US (a) and the Netherlands (b). The green bars (resource use) are primarily associated with fossil fuel derived NOx emissions from the housing, mobility, goods and services sectors. The blue bars represent the N that is consumed by the average person in the plant, dairy/eggs/fish and meat food groups. The red bars represent the N lost to the environment before consumption due to the production of those food groups.

Although the total amount of nitrogen (i.e., protein) consumed per capita in the US and the NL is about the same, the sources of protein are different. More protein in the Netherlands comes from the dairy/eggs/fish category, whereas more protein in the US comes from the meat category. Because more nitrogen is released to the environment throughout the food production process for meat, the total food production N footprint for the US is much larger.

The food sector is ultimately responsible for more nitrogen losses than any other sector. Food production, which accounts for all of the nitrogen released get a food product to a consumer's plate, releases much more nitrogen to the environment than food consumption, which includes the losses after the food is consumed. Of the different food types, meat products are responsible for the most nitrogen losses because there are so many pathways throughout the meat production process through which N can be lost.

Galloway and Leach also recommend ways to reduce your N footprint. Although some aspects, such as electricity production, are mostly out of a user's control, users can make a number of decisions to change their nitrogen footprints, such as:

  • Choose foods that are produced on more sustainable farms
  • Reduce your overall food consumption if you currently over-consume protein
  • Reduce your meat consumption or replace meat protein with other protein sources
  • Limit your household utility usage by using more efficient appliances
  • Choose more sustainable transportation methods like carpooling, public transit, bicycling, or walking
  • Reduce your consumption of goods by limiting unnecessary purchases, reusing, and recycling

Next steps

Galloway and his team will publicly launch the N-Print website and the N-Calculator tool in the summer of 2010. They are currently developing versions of the N-Calculator for the following countries: India, Germany, UK, China, and Tanzania. They also plan to present the N-Print project at the Fifth International Nitrogen Conference (December 2010).

Participating organizations:


For more information, please contact Alley Leach (aml4x@virginia.edu).

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