How phosphorus shortages could increase global food prices

| 28th October 2011
Peak phosphorus
Phosphorus is a crucial nutrient and a vital component of fertiliser, a mainstay of modern farming. But we could be heading for a major shortfall in supplies, argues Hannah Hislop, with some alarming consequences

Even if you’ve heard of it, you probably don’t know what it looks like or  have ever handled it directly. But phosphorus is one of the major nutrients needed to sustain life, it plays a crucial role in energy metabolism, membranes, structural support such as teeth and bones, genetic components and photosynthesis.

Modern agriculture is almost completely dependent on the mineral source of phosphorus, phosphate rock. Few, if any, cultivated soils can support prolonged intensive farming without it, or its secondary sources. And, as the new Green Alliance report on resource security argues, we may be sleep-walking towards a new era of phosphorus insecurity that could spell the end of cheap fertiliser, and have profound implications for global food prices.

Throughout agricultural history, up until the middle of the 20th century, humans largely relied on manures, and human and animal wastes, to fertiliser land and grow food. But after the Second World War, the use of phosphate rock for fertiliser production rocketed by over 1000 per cent, making a crucial contribution to steadily increasing agricultural yields, and thus human population growth, ever since.

Although phosphorus can be recovered, reused and recycled, it is both finite – phosphate rock takes many millennia to form – and un-substitutable. Given these facts, you might think that governments and global institutions would be falling over themselves to work out just how much phosphate rock there is left, where it is, and what can be done to make these finite supplies stretch a lot further. But this debate seems to be happening entirely out of the political and public spotlight.

In particular, there is disagreement about the size of global phosphate rock reserves and thus the likelihood and timing of ‘peak phosphate’ (i.e. when phosphate production reaches a maximum rate, after which it starts to decline). The International Fertiliser Development Centre published research in September 2010, based on new reserves estimates by the US Geological Survey, which argued that there are sufficient phosphate rock reserves to produce fertiliser for the next 300-400 years. Their findings have been disputed by a group of scientists at the Global Phosphorus Research Initiative, who query the data, and argue that even if the new reserves estimates are accurate, they would still expect peak phosphate within this century.

However the debate about peak phosphate is resolved, the most convincing argument to take far more notice of this resource is that security is about far more than physical scarcity. That there is such uncertainty and disagreement about the size of global reserves is concerning enough. But other factors play a significant role in increasing the insecurity and risks around this resource:

• Demand for phosphate rock is closely linked to population growth and therefore expected to increase as the population heads from 7 billion now to over 9 billion by 2050. This increase will be further exacerbated if there are increases in crops grown for biofuels and the shift towards meat and dairy-intensive diets in emerging economies continues.


• The geopolitics of supply and demand also determine the security of this resource. While all farmers need phosphorus for their crops, a very small number of countries – in particular Morocco and Western Sahara, control the majority of the world’s phosphate rock reserves, and some have imposed export restrictions in recent years.

• Quality declines and environmental and energetic costs increase as we use up the best reserves of phosphate rock. Those remaining contain decreasing concentrations of phosphate and increasing concentrations of impurities and heavy metals such as cadmium, which are then transferred to agricultural soils. Mining of more diffuse sources also increases pollution, waste, and water and energy consumption, and overall cost.

• Even at today’s prices, farmers in developing countries cannot afford phosphate fertilisers, and so under-apply, despite low soil fertility. A market response to scarcity, i.e. higher prices, could have devastating consequences for food prices and thus food security, unless there is significant development of phosphate recycling to substitute the use of mineral phosphate. It’s clear that far more national and international attention is warranted on a resource so crucial to global food security.

At the moment we view secondary sources of phosphate, such as animal and human excrement, as pollutants and waste, and so design nutrients policy, where it exists at all, to limit the damage to water bodies from fertiliser run-off or sewage. But to also tackle our dependence on this finite resource, we need to start reusing, recovering and recycling phosphorus already in the system. This is a massive, systemic challenge and will therefore require action at many different parts of the supply chain, including:

• Reducing demand for phosphate fertiliser, both through better agricultural practices, a shift in the fertiliser industry from selling a product (fertiliser) to selling a service (soil fertility). The need to reduce demand for phosphate fertiliser is yet another reason why a shift away from meat and dairy-intensive diets would be desirable.

• Reusing secondary sources of phosphates through the spreading of treated sewage sludge, animal manure and the outputs of anaerobic digestion and composting operations on agricultural land. This will require better recognition of, and incentives for, the use of good quality nutrient products on land to displace the application of phosphate fertiliser.

• Recovering more phosphate from sewage works through a shift from chemical to biological nutrient removal techniques. Again, this shift will require policy to incentivise or require this switch.

Perhaps the biggest obstacle, however, will be our apparent squeamishness when it comes pretty much anything to do with dealing differently with our waste. The government is already running scared of the Daily Mail when it comes to asking people to separate their food waste. In the Indian state of Tamil Nadu, users of a community composting toilet get paid per visit in recognition of the fertiliser value of their waste. A future where human excrement has a positive value may be nearer than we think.

Hannah Hislop is a senior policy adviser at Green Alliance and co-author of Reinventing the wheel: a circular economy for resource security.

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