- Use of phosphate fertilizer is on the rise but its raw material is depleting fast
The world faces an imminent crisis in the supply of phosphate, a critical fertilizer that underpins the world’s food supply. Phosphate is an essential mineral for all life on earth and is added to farmers’ fields in huge quantities. But rock phosphate is a finite resource and the biggest supplies are mined in politically unstable places, posing risks to the many countries that have little or no reserves.
Phosphate use has quadrupled in the last 50 years as the global population has grown and the date when it is estimated to run out gets closer with each new analysis of demand, with some scientists projecting that moment could come as soon as a few decades’ time.
Researchers say humanity could only produce half the food it does without phosphate and nitrogen, though the latter is essentially limitless as it makes up almost 80% of the atmosphere.
“Phosphate supply is potentially a very big problem,” said Martin Blackwell, at Rothamsted Research, an agricultural research centre in the UK, and lead author of a new study. “The population is growing and we are going to need more food.”
At current rates of use, a lot of countries are set to run out of their domestic supply in the next generation, including the US, China and India, he said. Morocco and the Moroccan-occupied territory of Western Sahara host by far the largest reserve, with China, Algeria and Syria the next biggest, together representing more than 80% of global rock phosphate.
“In a few years’ time, it could be a political issue with some countries effectively controlling the production of food by having control of rock phosphate supplies,” Blackwell said. “There should be a lot more effort being put in so we are ready to deal with it. It is time to wake up. It is one of the most important issues in the world today.”
Prof Martin van Ittersum, at Wageningen University in the Netherlands, said problems would begin before the mineral is exhausted: “Well before we run out of phosphate, the resource may become much more expensive.”
Potential solutions include recycling phosphate from human sewage, manure and abattoir waste, new plant breeds that can draw the mineral from the soil more effectively and better soil tests to help end the over-application of the fertilizer.
Excessive use of phosphate is not only running down supplies but is also causing widespread pollution that leads to dead zones in rivers and seas. In 2015, research published in the journal Science cited phosphorus pollution as one of the most serious problems the planet faces, ahead of climate change.
The new study published in the journal Frontiers of Agricultural Science and Engineering states, “The continued supply of phosphate fertilizers that underpin global food production is an imminent crisis.”
It notes that an estimate of the remaining years of rock phosphate supply fell from 300 to 259 in just the last three years, as demand rose. “If the estimated remaining number of years supply continues to decline at this rate, it could be argued that all supplies will be exhausted by 2040,” the scientists wrote.
“While this scenario is unlikely, it does highlight those imminent fundamental changes in the global phosphorus trade, use and recycling efforts will be necessary,” they said. “This is especially pertinent in China, India and the US, the three countries with largest populations on the planet, which rely on rock phosphate to feed their people.”
The European Commission declared phosphate a “critical raw material” in 2014, an essential resource with significant risk to supply. Only Finland has any reserves in the EU and most is imported to the bloc from Morocco, Algeria, Russia, Israel and Jordan. “The EU is highly dependent on regions currently subject to political crisis,” according to an EC position paper.
Commercial phosphate fertilizer was invented at Rothamsted in 1842 by dissolving animal bones in sulphuric acid. Blackwell and his colleagues have returned to this source to investigate an alternative supply of phosphate.
They have turned bones, horns, blood and other abattoir waste into phosphate fertilizer and in new research found it worked as well or better than conventional fertilizer. Blackwell said it could potentially provide 15-25% of the UK’s needs. Another potential source is recovering phosphate from human sewage; Thames Water opened a plant doing this in 2013.
Van Ittersum said recycling phosphate from animal and human waste is vital, but that will take time to implement as new technology and regulation will be needed to ensure contamination and infection of food crops does not occur.
Reducing use is also key, said Blackwell. The soil tests available to farmers at the moment are not very advanced, he said, so farmers add extra phosphate to be sure. This means excess phosphate in most agricultural soils, estimated as representing a century’s supply.
But most of this soil phosphate is bound up in organic molecules and inaccessible to plants. Some plants produce acids and enzymes that can break these down, and scientists are using genetic modification to create new plant varieties that can access this phosphate. Van Ittersum said such research was urgent as it will take a lot of time to develop more efficient crops.
Phosphate expert Marissa de Boer said the lack of awareness means the issue is the “unknown” environmental crisis: “We really depend on phosphate but we take it for granted.”
De Boer ran a five-year European Commission project on technologies to recycle phosphate and now runs SusPhos, a company looking to commercialize ways of extracting phosphate from human waste, food waste and industrial waste. She said recycled phosphate could meet the Netherlands’ needs if the technology proves successful: “As long as people have got to go to the toilet, and wastewater treatment is centralized, we can use our own phosphate.”