Circularity, Livestock, and Nutrients

What should the broad vision be to achieve circularity? Circularity – or applying the principles of ecosystems – is a big theme on this blog. I usually talk about indoor agriculture, but the same concepts apply to our whole food system.

Last week, I attended the NVTL (Nederlandse Vereniging voor Techniek in de Landbouw, or Dutch Society for Technology in Agriculture)’s annual conference. This year’s theme was circularity.

Professor Imke de Boer, Professor Martin van Ittersum and others have been working together on this for a while. Imke de Boer has recently achieved quite some fame for this fascinating vision on circularity. At the NVTL’s conference, Martin van Ittersum gave a presentation on this vision. It’s a very compelling way of looking at things.

Professor Martin van Ittersum at NVTL’s annual conference. Photo courtesy NVTL.

The Role of Animals in Circular Agriculture

The main reason for circularity – on a global level – is to produce food within the carrying capacity of our planet. There have been many approaches to quantifying this, but the most well-known is the footprint approach. Essentially, we must produce with a lower footprint, and consume with a lower footprint. However, this approach leads to some unanswered questions – especially for animal products.

If we are to produce with a lower footprint, that means increasing animal feed conversion efficiency. This requires high-quality food, which could be fed to humans instead – also known as feed-food competition.

What about consuming with a lower footprint? One approach is to replace red meat with white meat like poultry. However, this still does not eliminate feed-food competition. Another increasingly popular approach is to go vegan. But if we stop using animals in food production, what are we going to do with all those waste streams, which they could eat? Not to mention all that non-arable land which is currently being grazed. We would have to find new land to grow plant-based protein sources instead.

With this in mind, Martin van Ittersum and Imke de Boer came up with three guiding principles for circular agriculture:

  1. Use plant biomass to feed people instead of livestock where possible.
  2. Use by-products.
  3. Use livestock for what it is good at – e.g. turning waste into food, or for fertilising land.
A lovely flowchart of how our food system could be connected. Animals are used to turn waste into value and make use of non-arable grassland (De Boer & Van Ittersum, 2018).

The goal should not be to maximise the production per animal. Livestock should not be eating crops that could be fed to humans, which is currently the case. Instead, we should use livestock to upcycle by-products, which are there whether we like it or not.

A graph of land use against dietary grammes of animal protein per day. The minimum lies around 9-23 g, where less land is required than if everyone were to go vegan (De Boer & Van Ittersum, 2018).

With all of that in mind, it turns out that the most sustainable diet is not one free of animal products. In fact, the optimum lies at about 9-23 grammes of animal protein per day per person, depending on the kind of animal protein. Still, all the continents except for Asia and Africa are above this amount.

Animal protein consumption per continent. Only Africa and Asia are below the maximum of 23 grammes per day (Van Zanten et al., 2018).

Fertilising Crops: Are Animals Enough?

That’s one side of the story – what to do with by-products. The other side is how to fertilise crops. Animals can play a role here too, as they do in natural ecosystems.

Doesn’t this sound like returning to the good old days of using livestock to fertilise arable land? Pretty much. The problem is, though, that this is not necessarily sustainable.

Frans Aarts did a study of the farming practices used in the south of the Netherlands in 1800. Back then, livestock was the only source of fertiliser for arable crops. His conclusion was that nutrients ended up going from grasslands to the arable fields, exhausting the grasslands. This is happening in Subsaharan Africa now too.

Animals are only part of the solution. Martin mentioned PlantyOrganic, an organic pilot farm run by Wageningen Research. It aims to be 100% self-sufficient for nitrogen. No external nutrients are allowed – including from manure. Instead, PlantyOrganic uses nitrogen-fixing plants and crop rotation.

That said, even with manure, the organic approach leads to lower yields than conventional techniques. Not to mention maintaining crop rotations and nitrogen-fixing plants.

Not All Nutrients Are Created Equal: Are Chemical Fertilisers OK After All?

Because the organic approach would lead to lower yields, it would require more land – especially if no animal manure is used. Because of this, using inorganic fertiliser has sustainability advantages: it reduces the amount of land required to grow food.

But surely inorganic fertiliser is the enemy, to be eliminated at all costs? Well, it depends on the nutrient in question.

Take nitrogen, for example, a source of big debate in The Netherlands at the moment. Nitrogen is plentiful and mobile. Like carbon, it ends up in the air and can be taken up again. This is how nitrogen fertiliser is made, using the Haber process. We can afford to use inorganic fertiliser (as long as we don’t leach it into the environment too much).

Phosphorus is a different story, however. It is far less plentiful than nitrogen, currently coming from only a handful of mines in Morocco. It is also less mobile. There is no phosphorus gas in the air, for example.

A phosphate mine in Morocco, where 75% of phosphate is mined. Morocco World News.

In theory, the phosphorus cycle could be made circular, but there are far more challenges. Phosphorus will eventually get lost. Once this happens, it is a lot harder to recover than nitrogen. Because of this, recovering phosphorus is essential. This means getting it from manure – not only animal manure, but human excreta as well. That makes it tricky.

Feeding the World Within Planetary Boundaries

The presentation started with the usual story of how by 2050 the world’s population is expected to be around 9-10 billion. However, Martin then focused on Subsaharan Africa, where most of this growth is expected to occur.

In Subsaharan Africa, rainfed maize’s yield is only at 10-20% of its potential. It is increasing, at about 30 kg per hectare per year, but this growth rate is too slow to keep up with Africa’s projected population growth. Subsaharan Africa would only be self-sufficient if it got to 80% of its potential optimum yield. This would require huge changes.

How big is 80%, anyway? How is the rest of the world doing? Martin showed a map of Western Europe for wheat, from, a project he is leading. Only Denmark was in the category of 80-90%, but in general Western Europe is doing very well.

A map of rainfed wheat yields as a percentage of the theoretical maximum, on

Martin then said that Europe should play a leading role in the transition to circularity for two reasons. First of all, it is a good way to protect our environment. But secondly, if we don’t, who else will?

Practical Concerns and Conclusion

The first practical concern is the economics of all of this. For the time being, circularity is expensive. There are also legal/regulatory challenges. This is the case for the insect industry, but for circular agriculture in general as well. Hygiene must be guaranteed.

Another practical concern is scale. Waste streams need to be connected to animals, animal manure needs to be connected to plant production, and so on, but on what level? All under one roof? On a local level? Or within a region?

All in all, some interesting points from Professor Martin van Ittersum for feeding the world sustainably. Livestock and chemical fertilisers get plenty of criticism these days, but maybe they are not all bad. In fact, when used properly, they can help decrease agriculture’s land use.

One last remark Martin had was that the Dutch greenhouse horticultural sector is already managing nutrients very well, with precisely-controlled dosage and efforts to minimise leaching. However, the source of these nutrients still isn’t circular. This calls for aquaponics, doesn’t it?

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