Science Articles

Bigfoot: The Nitrogen Problem

Tue, 14th Aug 2012

How you can reduce the size of your nitrogen footprint...

Robinson Fulweiler

Bigfoot is the stuff of legends - a large, hairy, man-like creature that hides in the woods or high in a mountainous cave. Some believe he is a spiritual guide or an “elder brother” Dinosaur footprintssent to watch over us and warn us of our miss-doings. There are active groups who post sightings of this mythical being on websites and assemble to search for clues of his existence. But what if they are looking in the wrong place? Looking for the wrong creature? Looking for the wrong footprint?

I would argue that real bigfoot is the collective impact of human actions that have led to the doubling of amount of nitrogen cycling on earth. Together we leave behind a trail of environmental destruction that could rival any large track you might imagine. In the past three essays we explored the importance of nitrogen, how humans have altered the amount of it cycling in the biosphere, and some of the negative environmental changes that occur when excess nitrogen enters coastal systems. Now, I want to tell you about the top two ways you can reduce your nitrogen footprint.


First: you can make an impact by simply eating less meat. Nitrogen (N) pollution is largely driven by our consumptive habits. In fact, there is a strong correlation between a country’s wealth and their use of fertiliser, and between income and per-capita protein consumption (Nixon 1995). Protein consumption is important because it provides the nitrogen in our diets that we ultimately excrete into the environment. And while there are important cultural factors that dictate the types and amounts of meat consumed, the general global pattern is that meat consumption increases with wealth (Nixon and Fulweiler 2009).

Of course, the meat we consume, and the nitrogen we excrete in waste, is not the only concern. Another important problem is that our agricultural practices, in general, and the production of meat in particular, are remarkably inefficient. Of the 170 million metric tons of nitrogen (the equivalent of more than one and a half million blue whales) humans apply to cropland, only 12% actually ends up in our mouths (Galloway et al. 2003). In other words, it takes 100 kg (220 lbs) of nitrogen in corn to produce 5 kg (11 lbs) of edible nitrogen in beef — but the remaining 95 kg of nitrogen is lost to the surrounding environment (Nixon and Fulweiler 2009).

A recent analysis reported that the excess nitrogen in the environment costs the European Union between 100 and 460 billion Euros per year (Sutton et al. 2011). You needn’t go vegetarian, although that would help! Because by simply eating smaller portions of meat, or cutting back on the number of days each week you consume meat, you will decrease your nitrogen footprint.


Second: consume less energy. All of the nitrogen involved in energy production is lost to the environment. While you can’t alter how electricity is generated, you can change how you use it. Turn off your lights, buy energy efficient appliances, unplug electronics when not in use. To lessen the nitrogen release during the burning of fossil fuels simply turn down your heat in the winter and lower your air conditioning in the summer. Take public transportation or, better still, walk or bike to work: exercise and an environmental benefit rolled into one.

Key to success is that we convince our friends, family, maybe even the person next to us on the train to make these changes too. Individual actions are important but it is the sum of these actions that will deliver the most significant impact. Become the real stuff of legends. Become an environmental steward of our fragile coastlines and feel empowered — you can help create a sustainable future for all life on Earth...


Galloway, J. N. and others 2003. The nitrogen cascade. Bioscience 53: 341-356.

Nixon, S. W. 1995. Coastal Marine Eutrophication - a Definition, Social Causes, and Future Concerns. Ophelia 41: 199-219.

Nixon, S.W. & Fulweiler, R.W. (2009). Nutrient Pollution, Eutrophication, and the Degradation of Coastal Marine Ecosystems. In: C.M. Duarte, J. Culberston et al. (ed). Global Loss of Coastal Habitats: Rates, Causes, and Consequences. Bilbao: Fundacion BBVA. 184 p.

Sutton M.A., Oenema O., Erisman J.W., Leip A., van Grinsven H. and Winiwarter W. (2011). Too much of a good thing. Nature 472, 159-161.

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Livestock is relatively inefficient compared to vegetable diets as one has to grow the grain crops first which is then fed to the livestock, with perhaps a 10% efficiency.  However, often livestock can be foraged in marginal, non irrigated land that would otherwise not be put into agricultural use.  So, while the conversion efficiency may be poor, we may not be competing for a few blades of grass scattered between sage brush.

Animal manure is often used with organic gardening.  But, it is a good point that the nitrogen burden, especially with respect to our rivers and oceans is not insignificant. 

Different plants can be good or poor with nitrogen fixing.  Clovers and legumes can be some of the best, and may be good to plant with other crops, or for crop rotation.  Apparently much of the nitrogen fixation is due to varieties of Rhizobia bacteria.  I was reading about hemp production earlier which I believe suggested inoculating the hemp seeds with a subspecies, Bradyrhizobium bacteria before planting.  I presume different plants will either function well, or poorly with the bacteria.  It still releases ammonias into the soil, but perhaps less would leach into the streams and rivers. CliffordK, Wed, 15th Aug 2012

Plants that host Rhizobacteria in their root nodules are well placed to capture the nitrogen straight into their circulation, and into the soil. This should produce less runoff than spraying fertiliser on the soil. evan_au, Mon, 3rd Sep 2012

I did try to plant a row of mixed peas and corn this year.  For some reason, that row of mixed peas and corn, neither seemed to do well, which puzzles me greatly.  I think I'll have to do some more experiments next year to verify, as well as mixing clover and corn. CliffordK, Sun, 16th Sep 2012

Eating homegrown and organic as well as cutting meat out of your diet will certainly improve your N footprint, but another consideration is how much overall protein you consume.  Most Americans eat WAY more protein than their body can metabolize.  I believe a 150 lb person can use around 50-60 g protein per day. 

About the N-fixing plants:  Keep in mind that legumes and other plant with symbioses for fixing atmospheric N use that N to build more tissues, especially those high protein seeds we love.  In a natural environment, the tissues would die and the nutrients would make their way into the soil.  In the case of crops, such as peas and soybeans, farmers and agriculturalists not only remove the fruit, but all aboveground biomass.  When this happens, almost all of the N is removed from the system and therefore will not benefit the soil.  There are, of course, N fixers that live in the soil.  This might be one way to bypass fertilizers.

The Galloway paper cited in the above paper is very helpful for anyone looking for further reading about the N cascade. rhiza, Mon, 17th Dec 2012

More information on the N-cycle (in theNetherlands, Europe and worldwide can be found at A very informative infographic on the N-cycle and the loss due to manure: Gert Eggink, Fri, 21st Dec 2012

Presumably, grass-fed beef requires less fertiliser than corn-fed beef, and so should be cheaper.
Why then do they advertise beef as being "grain-fed"? evan_au, Wed, 26th Dec 2012

In the USA, Marbled Fat is popular. It is beyond me why,  as many people also wish to get low fat cuts.  However, the fat likely adds both to the flavor, as well as the tenderness of the beef.

I assume that "range fed" beef is done with minimal fertilizer on marginal land.  However, it is common to at least fertilize hay fields.

CliffordK, Sat, 19th Jan 2013

Seems to me that one of the worst wastes of fertilizer is on lawns.  People just want it to be green. Nitrogen and phosphorous is going into the environment for no good reason.  Personally, I think lawn fertilizers and most of the other lawn chemicals ought to be outlawed. Robert Dinse, Fri, 19th Apr 2013

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