Frequently Asked Questions

 

1) Why is nitrogen important?

2) What is reactive nitrogen?

3) What is virtual nitrogen?  How is it calculated?

4) What is tertiary sewage treatment?  How can I know if I have it?

5) What can I do to influence my N footprint?

6) What else can I do to reduce nitrogen pollution?

 

 

 

 

1) Why is nitrogen important? 

 

Nitrogen (N) is one of the building blocks of life: it is essential for all plants and animals to survive. Yet despite making up 80 percent of our atmosphere, none of nitrogen in the air we breathe is accessible to us. Like being lost at sea and dying of thirst, we are surrounded by nitrogen yet unable to use it in this “inert” form.

 

Humans and other life require nitrogen in a “fixed,” reactive form. The amount of reactive nitrogen available served as a cap on the amount of plant life, and thus food, that could grow until researchers discovered a way to manufacture reactive nitrogen. This discovery one hundred years ago has allowed food production to keep up with the growing human population, but at a high cost.

 

Today, reactive nitrogen has dramatically increased in our air and water. It comes primarily from agricultural activities such as fertilizer use and manure runoff, and the burning of fossil fuels.  This “nitrogen pollution” causes profound environmental impacts, including smog, acid rain, forest dieback, coastal ‘dead zones’, biodiversity loss, stratospheric ozone depletion and increased greenhouse gases. It also affects human health, including respiratory disease and an increased risk for birth defects.

 

Globally, humans are the main contributor of reactive nitrogen to the environment—far more than all the natural processes combined on continents. In contrast, human activity contributes just 5-10% of CO2  emissions. Part of the problem with nitrogen is that in most of the industrialized world, chemical nitrogen fertilizer use is highly inefficient, with 80% of the reactive nitrogen draining off the fields into nearby rivers and streams, or evaporating into the air.

 

Fortunately, we know how to solve the problem. This Nitrogen Calculator can help identify ways we can all work to reduce our nitrogen footprint, while continuing to benefit from its life-giving properties.

 

 

2) What is reactive nitrogen?


Reactive nitrogen (Nr) includes all forms of nitrogen that are biologically, photochemically, and radiatively active.  Compounds of nitrogen that are reactive include the following: nitrous oxide (N2 O), nitrate (NO3 -), nitrite (NO2 -), ammonia (NH3), and ammonium (NH4 +).  Reactive forms of nitrogen are those capable of cascading through the environment and causing an impact through smog, acid rain, biodiversity loss, etc. 

 

The non-reactive form of nitrogen is N2  and makes up about 80% of our atmosphere.  This form of nitrogen does not contribute to the environmental impacts noted above. 

 

Unless otherwise noted, the term “nitrogen” or “N” on the N-Print website refers to “reactive nitrogen” – not its non-reactive diatomic form.

 


3) What is virtual nitrogen?  How is it calculated? 

 

Nitrogen as a fertilizer is used to grow food. Some of the fertilizer N is taken up by the plant, and after processing only some of that N actually makes it into the final food product (embodied N). Virtual N is the rest: any nitrogen that was used in the food production process and isn’t in the final food product that you consume. Much of it either runs off of the soil into nearby waters or is lost to the atmosphere; virtual nitrogen is calculated to include the entire food production cycle and includes crop losses, animal waste and more. Once all of these inputs and releases are tallied, the nitrogen that you consume in your food can be subtracted out; leaving the remaining amount as virtual nitrogen.

 

Different food products demand different amounts of nitrogen inputs and have varying nitrogen use efficiency, which determines how much of the nitrogen is released into the environment.

 

 

4) What is tertiary sewage treatment?  How can I know if I have it? 

 

Most municipal sewer systems in the United States have primary or secondary treatment, which filter the human waste and break down its biological content.  However, this level of treatment does not remove most of the reactive nitrogen. Only about 5% of homes in the US are attached to municipal sewer systems with tertiary treatment, which further break down waste to a non-reactive form (N2) that does not harm the environment.

 

Knowing the level of sewage treatment at your local sewage treatment plant is very important because it can impact your N footprint by about 10%.  To find out if you have tertiary sewage treatment, contact your local municipal sewage treatment plant.

 

 

5) What can I do to influence my N footprint? 

 

While some elements like electricity production are out of your control, there are many things that you can do to reduce your nitrogen footprint. Here are a few, stratified by food and energy – aspects of the N footprint:

 

Food

  • Alter your diet: try to choose foods produced on more sustainable farms. These use practices that reduce their amount of nitrogen fertilizer runoff into the water and air. If they raise livestock, they take care to manage their manure so it doesn’t pollute.
  • A protein-heavy diet is nitrogen-intensive. The Dietary Reference Intake (DRI) recommendation is 0.36 grams of protein per pound of body weight per day for adults (or 0.8 g protein per kg body weight).  See page 4 of this document from the Institute of Medicine for more information. If you eat more than your recommended protein intake, try replacing some protein with other types of food like fruits, vegetables and grains.

 

Energy

  • 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 and services by limiting unnecessary purchases, reusing, and recycling

 

It is important to note that doing many of these things even just one day a week can make a big difference over time.  Most of these lifestyle changes will reduce not only your nitrogen footprint, but also your carbon footprint and your ecological footprint.  These changes will generally lead you to live a more sustainable life.

 

 

6) What else can I do to reduce nitrogen pollution?

 

We already know how to reduce our nitrogen footprint: use less nitrogen fertilizer, eat fewer energy-intensive foods, and try to minimize fuel-heavy forms of transportation, like airplane travel. These suggestions aren’t unique to reducing nitrogen pollution– many people trying to create more healthy communities are calling for these changes. You can go one step beyond your personal lifestyle choices and join others in calling for:

 

  • More renewable electricity choices from your local utility, such as wind and solar power
  • Increasing government support for sustainable farming practices 

 

For instance, there are current discussions in the US Congress about conservation measures within the national Farm Bill that encourage farmers to grow food more sustainably.  Let your local Representative know you support these measures. 

Please contact us if you have any questions or if you would like more information.

The N-PRINT projects are still in progress, so please come back soon to obtain updates.