Is Nitrogen the Next Carbon?


Battye, W. , Aneja, V. P. and Schlesinger, W. H. (2017), Is nitrogen the next carbon?. Earth’s Future, 5: 894-904. doi:10.1002/2017EF000592


You have probably heard about how carbon (in the forms of CO2 and CH4) is a major contributor to climate change. As you may remember, the way we use energy influences how much carbon is in the air and how large the impact is on global climate. However, burning fuel for energy is not the only way we impact the environment; how we grow food matters, too. So, have you heard about the problem of nitrogen pollution?

Agricultural Fields. Image credit: Thomas Nugent, Wikimedia Commons.
A New Revolution

Fertilizers, used by farmers around the world to increase crop yields, have helped us feed an ever-expanding population. We are undergoing a (third) Agricultural Revolution similar to the Industrial Revolution that lead to the sharp increase of carbon emissions: just as the Industrial Revolution made our lives better by having machines do labor-intensive tasks, the Agricultural Revolution is improving lives by providing nutrition to the billions of people that live on Earth today.

Nitrogen-rich fertilizers have been used for thousands of years. Until the last century when a process for creating nitrogen was developed, all fertilizer was naturally derived from animal waste such as manure and bat guano. This industrial nitrogen development has been an important part of increasing food production to feed the growing world population. The amount of reactive nitrogen produced by humans has increased rapidly in the last sixty years, almost fivefold. Reactive nitrogen refers to nitrogen in a form that can easily interact with other chemical compounds and can therefore impact air quality or plant life. There is a form of nitrogen, N2, that does not impact the environment. What we are discussing in this paper is nitrogen that interacts with the environment. There are environmental consequences associated with this reactive nitrogen, especially when it leaves farmlands and enters the air or waterways.


This figure from the original paper compares the increases in three forms of reactive nitrogen with carbon emissions. Image credit: AGU Open Access.

Similar to carbon, reactive nitrogen occurs naturally , but human activity is significantly changing the natural balance. The additional nitrogen from fertilizer has several negative effects. It can contribute to air pollution, which has health outcomes including heart disease and death. The additional nitrogen can also fertilize natural ecosystems, which may hurt the balance of plants and animals that are living in them, meaning some plants will grow too much leading to the death of some of the animals. Nitrogen can also contaminate drinking water supplies, which is harmful to infants. One of the most well-known issues is when rivers and lakes have too much nitrogen and excessive amounts of algae grow. In extreme cases, the die-off of algae can deplete the oxygen in the water, killing other lifeforms such as fish.

An algal bloom. Image credit: Felix Andrews (Floybix) -k, Wikimedia Commons.
The Future of Nitrogen

There is a lot we still don’t know about how nitrogen behaves outside of the farm. There are natural ways that the environment stores extra nitrogen that are not harmful, but scientists are unsure how quickly these systems can remove nitrogen, to balance what we are adding with fertilizers. Is there a limit to how much nitrogen can be stored? We have seen that some ecosystems certainly have a limit to how much nitrogen they can contain, such as lakes with algal blooms.

There are ways that we can help keep nitrogen at levels that we are confident the environment can handle. Scientists are working to increase the efficacy of the fertilizers themselves, so that farmers can achieve the same yields using less fertilizer. Good application techniques- like avoiding applying fertilizers before storms and planting trees to prevent erosion and washout- can help farmers to keep the nitrogen at work in their fields, too. On the livestock side, ranchers can take steps to keep animal waste from releasing nitrogen to the air and water. For those of you reading from a slightly more urban locale, steps like reducing food waste and eating foods that have low nitrogen impacts are available for you! Get ideas here. 

Both the Industrial and Agricultural Revolutions have shown that we can use our intelligence to improve our lives. We should use this intelligence to make sure that nitrogen and carbon in the environment don’t harm our quality of life.

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Kristen Brown

Kristen Brown

I am a postdoctoral researcher at the EPA where I specialize in evaluating environmental impacts of our energy system. I have a PhD in Environmental Engineering from CU Boulder where I also received a master’s in Mechanical Engineering, and I have a BA in Physics from Cal Berkeley. Outside of work, I’m an amateur boxer and have two spoiled dogs. You can follow me on twitter at @Kris10BrownPhD and find out about my research at

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