Phosphorus | How It Impacts Food Security

Have you heard of phosphorus? It's a naturally abundant mineral, essential for the growth of plants. Although it naturally replenishes, the slow regeneration cycle of phosphorus reserves has led to concerns over improper management and unsustainable extraction for use in agricultural fertilisers. Discover how this might impact future food systems.

Why agriculture needs phosphorus

Much like us, plants require macro and micronutrients to grow. Phosphorus, the 11th most abundant element in the earth’s crust, is a pivotal macronutrient in providing the energy needed for plant growth. By consuming plants as food, humans and animals can access phosphorus that would be biounavailable in the soil without the work of plants. 

Interestingly, while humans and animals need phosphorus as a key mineral for life, almost all of it consumed via food is excreted.¹ In the past, this excreted phosphorus would return to the soil in the form of manure, and plants would once again use it for their growth. But traditional methods of returning phosphorus to the soil, such as composting and using human and animal waste as fertilisers, have been largely replaced by modern methods that enrich the soil faster. Modern agriculture, focused on high intensity and high output, therefore breaks with the natural phosphorus cycle. 

Today, the majority of industrial crops receive most of their phosphorus from synthetic fertilisers. This phosphorus comes from phosphate rock, a finite resource extracted from the earth’s crust.¹ Formed over millions of years, the mineral-rich rock is concentrated in a select few parts of the world, such as Morocco, China, South Africa, Jordan, and the United States.¹ Currently, the phosphate rock is being extracted and traded at a rapid pace. This is being done to produce enough fertilizer to obtain high crop yields from limited agricultural land.

Depleting reserves, rising prices 

In the 1950s/60s, the Green Revolution sought to increase worldwide food production through agricultural intensification to improve global food security. A common way to successfully achieve intensification is to increase inputs of fertilisers, mainly nitrogen, potassium, and phosphorus.² Nitrogen fertilisers can be produced from atmospheric nitrogen, which is available in abundance (though it requires a lot of energy, traditionally coming from fossil fuels).³ Potassium and phosphorus are both limited resources, with phosphorus being a bigger concern than potassium.² 

While there is no consensus about when we will run out of phosphate rock resources in the future, most researchers investigating the issue agree that the pace of phosphate extraction is unsustainable and will lead to consequences for future food production. While phosphorus is never truly removed from the natural cycle, it can become hard to recover for long periods. For instance, if it enters lakes or seas, it binds with other compounds and ends up as sediment at the bottom of these water bodies. Recovering this phosphorus for use in agriculture is economically and technologically challenging. 

Experts also estimate that the economic, social, and political implications of phosphorus scarcity are likely to begin well before reserves run out.³ These challenges may be unprecedented for humanity because we have never faced the threat of a vital, non-replaceable element running out. The closest comparison to the challenges this would present can be seen in the case of the depletion of fossil fuels. But while fossil fuel depletion is being dealt with by developing alternative renewable energy sources, there are no known biological or technological substitutes for phosphorus.³

When will we see the impacts of phosphorous scarcities?

This scarcity will impact food production when the demand for phosphorus exceeds the supply and fertiliser costs start rising. Countries with no phosphorus reserves or are politically conflicted with phosphorus-exporting countries are likely to be the worst affected.³ Next to this, countries that have phosphorus reserves may not be able to access them due to various economic and developmental factors. Africa, via Morocco and Western Sahara, is the world’s largest exporter of mineral phosphorus. However, this does not mean that African countries can access phosphorus easily. Compared to Europe, phosphorus fertiliser is more expensive in sub-Saharan Africa in terms of its relative price and as a portion of a farm’s budget.³ Despite being a producer, many African countries cannot afford to purchase sufficient phosphorus for their agricultural needs and suffer acute food shortages.

Advocating for increased transparency 

The phosphorus supply chain is often described as a black box. It is estimated that as much as 80% of the phosphate rock is lost during its journey from the mine to our plate.⁴ However, the lack of reliable data makes it difficult to determine where and how exactly it is wasted. In the past, it was thought that adding excess phosphorus to soil was beneficial because it would remain in the soil for years to come, improving the fertility of the soil in the region.⁵ We now know that this is not the case. Instead of accumulating, excess phosphorus in soils is generally lost through leaching and surface run-off, often ending up in freshwater bodies.⁵ This leads to eutrophication, where high nutrient or mineral loads lead to excessive algal growth in lakes, reservoirs, and other stagnant potable water sources. Eutrophication blocks the inflow of oxygen in the water body, disrupting ecosystems and creating dead zones.⁴ Improved transparency in reporting about phosphorus use on farms and earlier in the supply chain can provide valuable insights, preventing phosphorus from being wasted.

Phosphorus and its social issues

Next to environmental concerns, the phosphorus supply chain is also known to be afflicted by social issues. Morocco, the world’s largest exporter of phosphate, has been known to violate international law and procure a quarter of its exports from the disputed region of Western Sahara.⁴ It has also been accused of violating the human rights of the Sahrawi people, who are indigenous to Western Sahara, by operating phosphate mines in their native land while not providing fair employment opportunities. Transparent reporting in the phosphorus supply chain would allow for better-informed policymaking on food security, water pollution, and human well-being.⁴

What solutions and strategies are there? 

Averting a global phosphorus crisis will require systematic change in how we grow, fertilize, process, and transport food.³ Some strategies that could help include applying fertilisers in moderation, bioengineering crops that require less phosphorus than traditional varieties, preventing run-off losses from fields, and returning non-consumable parts of the crops to the soil to compost instead of feeding them to livestock.³

Although more complicated than previously mentioned solutions, better human waste management can also improve the situation. Urine, rich in phosphorus, could provide half of the phosphorus necessary to grow cereal crops.⁶ This would require major infrastructural changes in the way sewage systems are planned because urine must be separated from faecal matter to be safely used as a fertilizer on farms.⁷

Sweden is a global pioneer in collecting human urine for use in agriculture. By adapting the sewage system in various parts of the country to divert and collect urine separately, Sweden has been able to use it as a natural fertiliser successfully.⁸ 

To implement these solutions, phosphorus scarcity must be recognised as an important issue warranting the attention of international organisations and national governments. Governance structures that ensure the equitable and sustainable use of phosphorus resources in the long term are vital if we want to ensure that the food system of the future is capable of feeding our rapidly growing population.