The nitrogen footprint of organic food in the United States

Laura Cattell Noll,Verena Seufert,Jan Willem Erisman,James N Galloway,Jessica Shade,Brooke Atwell,Allison M Leach

doi:10.1088/1748-9326/ab7029

Abstract

We estimated the reactive nitrogen (Nr) lost per unit food Nr consumed for organic food production in the United States and compared it to conventional production. We used a nitrogen footprint model approach, which accounts for both differences in Nr losses as well as differences in productivity of the two systems. Additionally, we quantified the types of Nr inputs (new versus recycled) that are used in both production systems. We estimated Nr losses from organic crop and animal production to be of comparable magnitude to conventional production losses, with the exception of beef. While Nr losses from organic vegetables are possibly higher (+37%), Nr losses from organic grains, starchy roots, legumes are likely of similar magnitude to conventional production (+7%, +6%, −12%, respectively). Nr losses from organic poultry, pigmeat, and dairy production are also likely comparable to conventional production (+9%, +10%, +12%, respectively), while Nr losses from organic beef production were estimated to be higher (+124%). Due to the high variability and high uncertainty in Nr efficiency in both systems we cannot make conclusions yet on the statistical significance of these potential differences. Conventional production relies heavily on the creation of new Nr (70%–90% of inputs are from new Nr sources like synthetic fertilizer), whereas organic production primarily utilizes already existing Nr (0%–50% of organic inputs are from new Nr sources like leguminous N fixation). Consuming organically produced foods has little impact on an individual’s food N footprint but changes the percentage of new versus recycled Nr in the footprint. With the exception of beef, Nr losses from organic production per unit N in product are comparable to conventional production. However, organic production requires the creation of less new Nr, which could reduce global Nr pollution.

Highlights

Humans create reactive nitrogen (Nr; all chemical species of N except N2) both for agriculture and from energy production [1]
Conventional production relies heavily on the creation of new Nr (70%–90% of inputs are from new Nr sources like synthetic fertilizer), whereas organic production primarily utilizes already existing Nr (0%–50% of organic inputs are from new Nr sources like leguminous N fixation)
We examine the N footprint of organically produced foods and compare it to the conventional food N footprint for the United States (US) Our objectives are to: (1) quantify the virtual N factors (VNFs) of organic crop and animal production in the US; (2) calculate the N footprint of a 100% organic diet in the US; (3) assess how much new Nr organic agriculture contributes to the global Nr pool, as a percent of total inputs; and (4) compare these results to conventional production

Summary

Introduction

Humans create reactive nitrogen (Nr; all chemical species of N except N2) both for agriculture and from energy production [1]. In the last 75 years, anthropogenic Nr creation has helped to dramatically increase agricultural yields and, along with it, feed a growing human population [2]. Most Nr used in agriculture is lost to the environment during food production [2]. This Nr moves through the nitrogen (N) cycle and creates a cascade of detrimental environmental and human health impacts [3]. Some suggest that we have surpassed the planetary boundary for Nr creation [4–6]. The N challenge consists of maximizing the benefits of Nr, while minimizing its negative impacts

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Conclusion