environment science

What’s your nitrogen footprint?

nitrogenWhat’s your nitrogen footprint? Chances are that’s a question you’ve never asked, but scientists are beginning to quantify our nitrogen use in detail, and I read the term nitrogen footprint for the first time this week.

There are, you may remember, nine global-scale environmental problems, according to the recent work on planetary boundaries. When I was writing about them last year, one of the things that struck me is how unknown some of them are. Climate change we hear about every day. Most of us are aware of the ozone layer and biodiversity loss, and we may have heard about ocean acidification and aerosols without knowing much about it. But human disruption of the nitrogen cycle? That’s hardly on the radar.

The nitrogen cycle is critical to life, but the element is relatively rare in its active form. Or at least it was until we discovered how to synthesize it 100 years ago. We now release 120 million tonnes of nitrogen into the wild through agriculture – “more than all of the Earth’s terrestrial processes combined,” as the planetary boundaries study points out.

This does wonders for our food production, but not all of it goes into plant growth. Huge amounts of it are ‘lost’ into the wild, overloading ecosystems with excess nitrogen and causing a host of air, water and land pollution problems.

Last Friday saw the release of the European Nitrogen Assessment Special Report on Nitrogen and Food, or the executive summary at least. It is part of a broader working group on nitrogen, in this instance focusing on the impact of our food choices. Their headline finding is that total nitrogen emissions are far higher from meat and dairy production than from plants grown for food. Once crops grown as animal feed are included, the nitrogen losses from beef “are more than 25 times those from cereals.” They suggest that if the EU halved its meat consumption, it would knock 40% off CO2 emissions from agriculture, 40% off nitrogen emissions, and free up large amounts of land for food crops and exports.

This is interesting, as the case for eating less meat has been made for a whole bunch of reasons, including climate change, animal welfare, and human health. To that list we can now add nitrogen pollution.

As for nitrogen footprints, I suspect it’s not a term that will be widely adopted, or certainly not anytime soon. There’s precious little consideration of carbon footprints as it is, and those are much better understood. Unless people are looking for some new environmental boy scout badge, I don’t suppose the idea of personal nitrogen footprinting will get very far.

And, the good news is that it probably doesn’t have to. There are good reasons to eat less meat already, and that looks like the thing that would make the biggest difference. Another is food waste, and a compelling case can be made for reducing food waste without ever mentioning nitrogen loss. One area where we might make a deliberate decision is in choosing organic food, but there are other factors there too.

I might be wrong – and please say so if you think I am – but perhaps we can live without worrying about our personal nitrogen footprints. But if you do want to know yours, then yes, there is an online nitrogen footprint calculator.


  1. I agree. If we reduce meat consumption than the CO2 and nitrogen issues will take care of themselves.
    Eating less meat is a challenge. I’m pretty good at cutting meat out for breakfast and lunch, but at dinner time I need some beef or chicken.

  2. I agree, nitrogen is cycled, so in its biologically active forms its lost in the soil back to nitrogen gas as bacteria use it as a terminal electron acceptor in non-aerobic respiration. There can be local disruption though due to excessive nitrogen fertilizer use and ecological problems. And of course we are addicted to fertilizer which takes large amounts of diminishing natural gas supplies to make. http://www.theoillamp.co.uk/?p=3919

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