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An Interview with Jim Galloway

Sep 01, 2013
Jim Galloway

Jim Galloway
Photo Credit: Jane Haley

A lot of your research deals with human alterations of the nitrogen cycle and resulting nitrogen pollution. What is nitrogen pollution, why is it a problem, and what has caused its development?

Nitrogen pollution occurs when reactive nitrogen (any nitrogen species other than N2) is present in amounts that cause negative impacts to the health of people or ecosystems.

The problems of nitrogen pollution are many-fold because of the nitrogen cascade. Once unreactive nitrogen (N2) is converted to reactive nitrogen by fossil fuel combustion (NOx formation), the Haber-Bosch process (NH3), or cultivation-induced biological nitrogen fixation (NH3), nitrogen is then spread around the Earth, contributing to problems associated with smog, acid rain, climate change, coastal eutrophication, and stratospheric ozone depletion, among others.

We are faced with the problems of nitrogen pollution due to extensive and growing resource use by humans that result in the formation of excess reactive nitrogen. The challenge to society is how to maintain the benefits of reactive nitrogen (food production!) without experiencing the problems of nitrogen pollution.


If left unchecked, what are some of the potential future consequences of nitrogen pollution?

Given that excess amounts of nitrogen in the environment due to human activities contribute to the nitrogen cascade and its associated problems, more reactive N in the environment will exacerbate those problems, and will create a legacy of problems for future generations to have to address.


What led to your interest in studying nitrogen pollution? 

My interest in nitrogen pollution began in the mid-1970s when I was investigating the processes that created acid rain, and its resulting impacts on aquatic and terrestrial ecosystems. Over the years, I kept going deeper and deeper into how people had altered the nitrogen cycle at local, regional and global scales, which led me to a more holistic approach on how humans could fix the problems that they had caused by their alteration of this major biogeochemical cycle.


The Nitrogen Footprint Model Paper you co-authored with Allison Leach and several other scientists recently received the ‘Best of Year’ Award by the journal Environmental Development. Tell us a little about what the Nitrogen Footprint calculator is, and what it can do.

The Nitrogen Footprint Calculator:  Calculate your own nitrogen footprint!

The Nitrogen Footprint Calculator: Calculate your own nitrogen footprint!

After years of working on the scientific aspects of the human alteration of the N cycle, I became convinced that a critical part of the equation on how to address nitrogen pollution issues had been left out—the consumer. So, beginning in 2008, my colleagues and I started to lay the groundwork for the Nitrogen Footprint Calculator. The N-Calculator is a tool that allows individuals to calculate their own nitrogen footprint and thus their personal contribution to nitrogen pollution. When using the N-Calculator, the person is asked questions about resource use in the following areas:

  • Food consumption
  • Housing
  • Transportation
  • Goods and services

The N-Calculator, which starts with the average per capita consumption of these four categories in a country, is then scaled to the individual based on the user’s answers to the questions. The N-Calculator then estimates the nitrogen lost per unit of per capita resource consumption. 

The production and consumption of food typically make up the largest proportion of a person’s nitrogen footprint. In the United States, food production and consumption make up 80 percent of the average per capita N footprint. 

Currently, there are N-Calculator tools available for the United States, the Netherlands, Germany and the United Kingdom. We are in the process of developing N-Calculators for other countries, including Japan, China, Tanzania, India, and Portugal.


How does the Nitrogen Footprint Calculator help people take charge of the amount they contribute to nitrogen pollution?

Once a person determines their own nitrogen footprint with the tool, they can then use it to run scenarios on how specific changes in personal resource use (e.g., type of food consumed, type of transportation used) will change their footprint.


Right now you’re working on a project with Ariel Majidi, Allison Leach, and Jessica Shade to determine how organic farming practices may alter people’s nitrogen footprint. Why do you think organic could alter the amount of nitrogen pollution produced by a farm?  What factors play into this thought process?

Organic farming practices have the potential to decrease the amount of N lost during food production for a number of reasons. Perhaps the most important is that it relies on the use of agricultural waste (crop residue and manure) as an input to the next production cycle. In a study that we are just completing, we found that the nitrogen lost to from the organic cropping system for starchy roots, grains, beans and vegetables, was 40-50 percent less than the nitrogen lost from conventional cropping system per unit of nitrogen in the crop.


How could this fit in with the Nitrogen Calculator, and what future steps need to be taken to enhance the Calculator?

We plan to use the results of the study to enhance the N-Calculator by having additional questions that allow the user to say what percentage of each food type consumed is produced by organic production practices. Another enhancement is that we will do a similar study for the production of animal protein, and then develop questions that will allow the user of N-Calculator to indicate how much of the various types of animal protein they consume is produced with organic practices.

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