We are running out of nitrogen and
this is how resilience can help

Reading time: 3 minutes

BY Hanny Roskamp

November 2018

Due to overconsumption, nitrogen in protein form is slowly disappearing from the food chain. With a smarter livestock system and a different way of eating meat, people are trying to turn the tide.

We only have one Earth and it is slowly dawning on us that it is a finite resource. In all sorts of areas we are reaching the limits of our once so resilient planet. In Nature magazine, environmental scientists recently attempted to calculate what our biggest ultimate threat is.

The answer they came up with was the disappearance of plants and animal species, the decline in biodiversity. The second biggest threat is the loss of the nitrogen cycle. We haven’t heard so much about that yet, compared to what we hear about CO2, climate change, plastic waste, and occasionally the shortage of phosphate for fertilizer. So what is the problem with nitrogen? Marieke Bruins is a specialist on the nitrogen cycle and is happy to explain.

PHOTO Frans Lemmens/Hollandse Hoogte

Researcher Marieke Bruins on solutions to the nitrogen problem: “We should start growing more beans and keeping less livestock.” Here we see the marginal broad bean harvest. PHOTOS Hollandse Hoogte

“Supplies of the element nitrogen are not easily exhausted. The air is full of it. But this problem concerns a particular form of nitrogen: the nitrogen that is fixed in proteins, the building blocks for all terrestrial life, both plant and animal. Leguminous crops such as beans and peas can fix nitrogen from the air (with the help of certain bacteria) and make protein out of it. Other plants get their nitrogen from fertilizer, natural or artificial.

‘The amount of protein in the food chain determines how many people and animals ‘fit’ on the earth’

This is how nitrogen gets into the plant-animal-human food chain. When people or animals eat proteins, they are broken down and the nitrogen leaves their bodies. That nitrogen disappears from the food chain, the biomass. The amount of nitrogen in the food chain determines how many people and animals ‘fit’ on the earth. At present, that amount is not enough for the growing numbers of people.”

Protein in grass

Marieke Bruins’ research focuses specifically on the cow, which often consumes more nitrogen than necessary. “Relatively, there is a lot of protein in grass, especially in the summer, and this is more than strictly necessary for the cow. That excess protein gets broken down into uric acid and gases such as ammonia, among other things. We are looking for way of using the protein in grass more effectively. The idea is to feed the protein from grass to pigs, that need far more protein, and then to feed the leftover grass fibre to cows. We do that with a large, powerful ‘slow juicer’.”

Marieke Bruins research focuses specifically on the cow, which often consumes more nitrogen than necessary. PHOTO Shutterstock

The underlying idea is that the resilience and shock-resistance of the livestock system will be increased. That we would rather eat beef than beans is not the only reason the nitrogen cycle is under pressure. Currently we import huge amounts of soya as an important source of protein for livestock. The soya industry is a burden on the rain forest and transports commodities across big distances, such as from Brazil to the Netherlands.

Import restrictions for soya

What would happen if soya imports were restricted? The protein from grasses could be one alternative. “Import restrictions are actually a disturbance to the system. But if that made it financially attractive to process grass for protein, the system as a whole could go in the right direction. That way biorefinery can help increase resilience.”

Grass mixed with clover provides more protein per kilogram. PHOTO Marcel Berendsen/Hollandse Hoogte

Bruins is working hard on calculations for all the different aspects of processing grass. Where is the trigger which makes it financially attractive to use this technique? And there are still technical hitches. “There is one mobile press, belonging to the company Grassa, which travels all around the Netherlands. They are still working on improving the technique. There is also research into the best mix to grow on grasslands. Grass mixed with clover, for instance, provides more protein per kilo, but a lower yield per hectare. The best mix might turn out to be very diverse, but we don’t know that as yet.”

‘Biorefinery can help make resilience go up’

Processing grass will not be enough to solve the global problems around livestock. Partly due to this understanding of the nitrogen problem, Bruins calls herself a ‘reducarian’: she still eats meat, but less. “We should start growing more beans and keeping less livestock. You can also pay attention to what kind of meat you eat. We are fond of beef, whereas a cow is particularly inefficient at converting its food into meat. The chicken does that a lot more effectively, and performs almost as well as soya. So switching to different animals helps too.”


Marieke Bruins PhD


Senior Biorefinery scientist at Wageningen University & Research

Resilience research

Research on the resilience of the nitrogen cycle


Marieke Bruins works on this research with a team of WUR scientists in the field of a sustainable and profitable livestock sector

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