Opinion: European agriculture is highly dependent on phosphate for fertilisation, but with supplies running out, we have to change our attitude towards waste and treat it as a valuable resource.

When it comes to nutrients that we apply to our fields to grow plants, phosphorus is unique. Unlike nitrogen that we can extract from the atmosphere at the expense of vast amounts of energy, phosphorus exists only in large amounts as natural resources in the ground of a handful of regions on our planet.

It can not be synthesised like nitrogen or substituted. Some places with phosphate resources are located in conflict areas such as the Western Sahara, and some are largely excluded from the international market to satisfy national demands such as China’s phosphate mines.

Others are expected to be exhausted within the next 30 years. Most importantly, none of them are located in Europe. European agriculture is therefore highly dependent on mined rock phosphate, imported from Morocco. It is expected that our world is going to run out of rock phosphate by the end of this century, similarly to the world’s oil reserves.

If we are about to run out of phosphate, what is going to happen?

Without fertilisation in agriculture, our crop yields will be dramatically reduced; we may experience widespread famines across Europe that we haven’t seen since the Great Famine in Ireland. That begs the question: what did people use before the green revolution to grow crops?

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The answer is that we used to have a circular economy of plant nutrients. Produced crops were eaten by humankind and their livestock alike and the so-called waste was used to fertilise the plants again.

Our so-called waste was recycled, and losses of nutrients to the groundwater, rivers and the seas was minimised. Currently, about half of the phosphorous we put on our fields is not recycled but is lost ultimately to the sea.

Unless we are happy to wait for the next geological events to take place and produce new rock phosphate over several millennia, we have to make sure that we stop the loss of our valuable phosphorus now. We have to change our attitude towards waste and see it as a valuable resource, waiting to be processed into the valuable products again.

So what is the solution – use all our animal and domestic waste on our fields? Luckily, we do not have to use animal slurry and wastewater sludge as raw materials to fertilise our fields. This would not work anyway as animal slurry is dilute and not suitable to minimise run off and loss of nutrients into the ground water.

A range of process are currently under development to improve the properties of what we currently call waste to make it more suited as a future fertiliser. Anaerobic digestion and industrial composting are only a few of them that are probably better known.

These and many other processing technologies will allow us to greatly reduce the loss of nutrients like phosphorus and thus will be a key factor for securing future food production.

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Current key hurdles are not necessarily the developments of these new technologies. We need more knowledge on how to use these new fertilisers more effectively. We have to overcome legislation that blocks us from using recycled materials.

Likewise, acceptance of farmers and consumers to use recycling-derived fertilisers to grow crops is a key factor. An interesting fact when it comes to phosphorus is that our soils are not necessarily deprived of phosphorus.

However, the amount of phosphorus in the soil that is plant available may be extremely low. Most of the plant-unavailable phosphorus is bound to soil particles, locked in minerals or are bound to organic matter. The microscopic lifeforms in our soils have the capacity to utilise these plant-unavailable forms of P.

The activity of soil microorganisms are a huge potential benefit for plants after phosphorus has been mobilised. Unfortunately, current intensive agricultural practices carried out by most of the farmers across Europe has a negative impact on our soil microorganisms and their functions.

In order to avert the current looming phosphorus crisis we have to ensure that we recycle and conserve as much phosphorus as we can and use our world rock phosphate reserves only as an occasional top-up rather than the primary source.

Furthermore, we need to ensure that the soil organisms which we have largely ignored are better promoted so that they can turn-over any plant-unavailable phosphorus more quickly than it is the case in current intensive farming systems.

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The new farming system we need will follow the ecosystem engineering principle, where we maximise the function of our ecosystem to grow our food and where we use recycled nutrient sources that are sustainably produced.

The EU has started to provide funding for several new research consortia that investigate the production and use of recycled fertilisers including Phos4You, Nutri2Cycle and Renu2Farm.

However, further research is needed to better understand the function of the microscopic soil organisms that turn plant unavailable phosphorus into plant available phosphorus. Key organisms for the turnover of phosphorus in soils are the bacteria, the fungi as well as their microscopic predators such as the nematodes and protists.

The study of their interactions, their functions as well as their diversity is not trivial. We are reasonably good at understanding how a few of these organisms operate in a lab environment.

However, soils are the most complex environments on our planet and a teaspoon of soil already contains over 100,000 different microbes as well as more bacteria than there are humans on our planet.

Europe’s future agriculture therefore has to integrate recycled fertilisers and soil organism functions into their Common Agricultural Policies to secure future crops production and avert the phosphorus crisis. 


The views expressed here are those of the author and do not represent or reflect the views of RTÉ.