When Talking About Climate Change, We Need to Talk About Nitrogen Too

When you hear the word environment in the context of sustainability, you know the word carbon isn’t far off – given that anthropogenic emissions of carbon dioxide are the largest contributor to global warming, the connection makes sense. However, the problem is that climate change is significantly more complex than emissions of carbon based greenhouse gases. By focusing on carbon too much, we ignore other problems which are also having a profound impact on our environment.

Nitrous oxide is a potent greenhouse gas

Although only responsible for 6% of our global greenhouse gas emissions, nitrous oxide is significantly more potent at warming our atmosphere than carbon dixoide – while the former has a global warming potential (GWP) of 265, the latter has a GWP of 1. This means nitrous oxide is 265 times more efficient at trapping heat in our atmosphere. Not only this, but this nitrogen based gas is also one of the more potent ozone destroying gases we still emit today.

The growth of the agricultural industry has increased the level of nitrogen pollution

However, the problems don’t stop there. Due to large increases in the world population about a century ago, there was an increased need for food. The only way to provide that food, was to increase the scale of our agricultural industry. Nitrogen is an important part of plant nutrition, and the natural source of that occurs through nitrogen fixation. Here, bacteria and archaea transform atmospheric nitrogen into ammonium, which is made into nitrites and nitrates in a step called nitrification. However, nitrogen fixation is the limiting step in plant growth. The Haber-Bosch process is a synthetic method of nitrogen fixation. The ammonium produced is then used in synthetic fertilisers, which has allowed us to grow food on the scale that we do today.

An algae bloom due to eutrophication. Source: eutrophication&hypoxia.

Since the dawn of this process, nitrogen fixation has increased significantly. This has spread nitrogen into our ecosystems. Around 30-50% of fertilisers will not be absorbed and run off into waterways. This then leaks into rivers, lakes and oceans. Eventually, this creates nutrient rich waters. While this may seem like a good thing, it is terrible for wildllife. Nutrient rich waters leads to eutrophication, which is the growth of dense plant life. Upon death, the decomposition process of these plants uses up all of the oxygen in the water. This suffocates the aquatic animals. In addition, excess nitrogen has been shown to reduce soil fertility, by removing essential nutrients like calcium and potassium. The formation of nitrous oxide is also a part of the nitrogen cycle. The breakdown of the nitrogen compounds in the fertilisers leads to emissions of it.

We need to change our food habbits to reduce nitrogen pollution

The key to reducing our nitrogen pollution lies in the food system, but what can we do? Don’t we have to eat, and aren’t people already starving? Isn’t the human population expected to grow? Well, one of the biggest problems and potential solutions, is that on a worldwide scale, we waste one third of all food produced. If we were to correctly utilise this one third, we could already reduce the need for nitrogen based fertilisers and hinder the negative outcomes described above. As one in nine people are starving, we could also use this food to rid the world of hunger.

In ambient temperatures of 40-45 degrees celsius, those in developing countries have to use traditional transport methods like rickshaws, open trucks, motorcycles and bicycles. Due to this, most food is wasted before reaching the market. Dr Sonal Choudary of the University of Sheffield is currently working on producing cooling transport technology by using space science and cryogenics.

In the West, one third of food ends up in landfill after it reaches the market.

In the West, the waste is due to our throwaway food culture and overproduction. Europe already has a plethora of solutions to prevent this from happening. For example, there are apps such as Olio or Too Good To Go – the former connects neighbours and encourages them to share food, whereas the latter is for picking up leftovers from restaurants. To compliment this, there are also many community based solutions. The Real Junk Food Project is one example. There, they save food from supermarkets and cooks a community meal with it.

However, the types of food we eat also have an impact. According to the landmark study by Joseph Poore at the University of Oxford, animal products provide us with only 18% of calories, yet they use 83% of farmland. This means that consuming animal products is responsible for a much greater proportion of our fertiliser use, and therefore nitrogen pollution. To prevent nitrogen pollution from becoming more of a problem, it’s important to talk about the way we deal with food, from what it is we’re eating, to how it is produced and distributed.

Popular science focuses on carbon dioxide

Perhaps there is a need for a villian in our Hollywood-centric society, but the overwhelming focus of carbon dioxide on climate change often overlooks other very important issues. At the same time, the vast majority of warming in our atmosphere is due to emissions of carbon dioxide, so it is important that decarbonisation is one of our top priorities. Regardless, any discussion we have about human activity on the planet must include a frank discussion on our food systems, not only due to the huge impact of nitrogen-based pollution, but also due to other aspects of the industry such as water use and carbon dioxide emissions. In creating a world for the future, it’s important we create a new cycle to support our natural ones: a cycle of sustainable human consumption.

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Jack McGovan is a recent graduate in chemistry with a specialisation in ‘Energy and Sustainable Chemistry’ from the University of Groningen, the Netherlands. Following a job as a student journalist covering the energy transition, he has moved to Berlin where he is following his passion for working towards creating a fairer and more sustainable world. Seeing a gap in the way in which the world of science was communicated, he founded Delta-S. By writing source based content, he hopes to communicate his findings to a wider audience.