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Lack of phosphorus puts global food security at risk

Phosphorus (P) is an indispensable element for life on Earth. Essential structures for any organism like DNA or RNA contain this element, and plants can not perform photosynthesis without it. Because of this, crops require huge amounts of phosphorus to meet the standards of efficiency and productivity needed to feed an ever-growing human population. However, this is a limiting and finite resource, and the predictions are not promising: reserves will be depleted in about 100-150 years. That will lead to significant geopolitical problems still unimaginable because, apart from the ephemeral nature of this resource, there is the fact that 90% of stocks are in the hands of only 6 countries. Conflict is served.

INTRODUCTION

Anyone who has ever had to buy fertilizer will recognize this sequence: N-P-K (nitrogen, phosphorus, potassium). They are the most used nutrients for gardening and plant production in general. Without them, plants do not grow or can not develop enough to persist in the long term. Of the three main nutrients, potassium is the most abundant in the earth’s crust (representing approximately 2.4% of the earth’s surface by weight), especially in ancient seabed and lakebeds, as well as being the most available for plants. On the other hand, nitrogen in its gaseous form is extremely abundant (78.1% of the air around us is molecular nitrogen), but not their molecules in solid form, which are usually scarce due to their high mobility throughout the soil. However, thanks to the Haber-Bosch process (which lead researchers to win the Nobel Prize in Chemistry), solid nitrogen (in the form of ammonia) was produced from gaseous nitrogen, leading to a high availability of this inorganic fertilizer.

haber_bosch_in_lab
Friz Haber (right) with a scientist who manipulates the Haber-Bosch method. This way of extracting the atmospheric nitrogen and turning it into ammonia is considered, by many scientists and historians, as the most important invention of the modern history. Without it, the world would not have been able to afford even half of the current food demand. Source: el juicio de fritz haber.

THE PHOSPHORUS CASE

Phosphorus, however, is the third party in discordance. Essential for life, it is the main component of DNA, RNA, ATP (the energy used in cellular processes) and phospholipids, which cover cell membranes. It is present in the bones and is involved in almost any animal biological process. In addition, it is imperative for plant growth: without phosphate, photosynthesis can not be carried out. The biggest problem with phosphorus is that it is not free in nature. Plants and, in general, all organisms, satisfy their phosphorus needs thanks, mainly, to another living organism: animals, from plants and, these, from animal residues or their corpses, which release the Phosphate in the decomposition process. In fact, the most important fertilizers until the arrival of inorganic fertilizers, already in the twentieth century, were the excrements and urine of farm animals, which contain a large amount of phosphorus, in addition to the other elements already mentioned. However, as a result of the Haber-Bosch invention and the increase in food demand as a result of population growth, phosphorus deposits, which are in the form of minerals and are actually scarce in the earth’s crust, began to be exploited.

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Guano accumulated on an islet of Peru. Guano, together with excrements and urine from farm animals, was an important source of phosphorus until the 20th century. This substrate, formed from continuous depositions of seabirds, seals and bats, is still very much appreciated even today, especially in organic farming. Source: Hiding in Honduras.

 

A SCARCE, IRREPLACEABLE, AND BAD-USED RESOURCE

Phosphorus is an irreplaceable and non-synthesizable resource. Reserves are finite and are being wasted, since much of the fertilizer applied is not assimilated by plants and, through the soil, ends up in the sea or in the lakes, where they unbalance the ecosystems. Being such a scarce resource, it is often the limiting resource in most ecosystems. For that reason, an overfertilization of phosphorus is often exploited by autotrophic algae to grow uncontrollably, which, in many cases, causes blooms that can generate important animal, economic and environmental losses.

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Extension of the vegetation of the Mar Menor (Murcia) in 2014 and 2016. 85% of the vegetation has died in less than two years, due to strong phenomena of eutrophication, in which phosphorus has played a key role. The excess of nutrients allows algae proliferation, which end up causing difficulties of light infiltration which, in turn, preclude phothosynthesis, causing the death of plants. Source: El País.

6 COUNTRIES CONTROL WORLDWIDE PRODUCTION

The United States Geological Survey (USGS) has estimated the world’s reserves of phosphorus at 71 billion tonnes. 90% of these are in the hands of 6 countries: Morocco (where, according to the USGS, 75% of the world’s mineral reserves are found there), China, Algeria, Syria, South Africa and Jordan. However, United States and, specially, China (accounting for 47% of world phosphate production), are the countries that are currently extracting more phosphorus from their deposits. This production has been increasing in the last years, and it will go to more in the coming decades. According to this recent article by Nature, it will be necessary to double, by the year 2050, the use of phosphate fertilizers to meet the demand of food, in a world where there will already be 9,000 million humans. But, by then, more than half of the phosphorus in the reservoirs will have been used. This study warned of the possibility that we were reaching the peak of phosphorus production, although new calculations estimate their peak around the year 2040. In any case, if we continue with the current production, the reserves will be depleted in no more than 100 years.

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World phosphate rock reserves by country. Morocco capitalizes on reserves, followed by China and Algeria. Around 90% of the world’s phosphorus reserves are found in Africa, which predicts a future in which this continent will play a very important role in the negotiations for this finite resource. Source: WRForum.

GEOPOLITICS ENTERS INTO THE SCENE

A symptom of the potential shortage of phosphorus in the not too distant future is the rise in phosphorus prices that has been observed recently due to rising demand. Between 2007 and 2008 the price of phosphate tons increased threefold from 2005 values, and cost up to 9 times more than in the 1970s. In addition, it has been estimated that by 2035 phosphorus demand will exceed supply, what will cause an increased prices and, with them, political tensions. No stranger to it, many countries are working on ensuring a supply of this valuable resource for a few more decades. China, for example, which is now the largest producer (what does not mean the holder of the largest reserves) has begun to impose 135% tariffs on its exports. The United States, on the other hand, has signed a bilateral free trade agreement with Morocco, which gives it the rights to exploit their long-term phosphate deposits. Taking into account that most of Morocco’s phosphate reserves are in Western Sahara (a region that has fought for its independence since its occupation in 1975), it is not surprising that the United States has always supported Morocco in the United Nations Security Council, vetoing any proposal in favor of the independence of Western Sahara.

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Rise of prices of different phosphate minerals. Prices are expected to rise in the coming decades, as phosphate deposits are depleted. Source: USDA.
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Estimation of the evolution of phosphoric rock production and the moment when it will reach the peak of production. Many scientists agree that reserves will last between 60 and 130 years. Source: Cordell et al., 2009.

THE SOLUTION IS TO GO BACK TO THE ROOTS

According to the latest estimates, phosphorus deposits will be depleted, affecting crops around the world. This decline in food production will have a global repercussion, especially in the poorest countries, the most susceptible to a possible decrease in food production. Failing to establish measures to reduce global population, the lack of phosphorus combined with climate change will lead to tense relations between many countries, leading to geopolitical conflicts on a global scale.

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According to Metson et al. (2016) a plant-based diet would help to reduce the phosphorus demand. According to their calculations, a vegetarian person requires approximately 4 kg of phosphate rock per year, almost 3 times less than a meat-based diet, which consumes about 11.8 kg of phosphorus per year. Source: Jeremy Keith.

For that reason, the main solution is to use phosphorus in a more rational way and to recycle it as much as possible. Today, around 80% of phosphorus is lost between the exploitation of the mineral, its transport and its application in the fields, which requires us to make a more sustainable use of this resource. However, the world food security will only be able to mantain its production by recycling. The main proposal would be to return to the beginning: to collect human excrets and urine, generated in cities and towns, to recover all that phosphorus that, in other conditions, would end up in the aquatic environment. Approximately 100% of the phosphorus consumed by mankind through food is excreted in excrets and urine. Collecting it would be like a double-edged sword: on the one hand we would satisfy the phosphorus demand of the crops and, on the other hand, we would avoid the eutrofization of waters due to the excess of these nutrients. Furthermore, a change in diet, prioritizing vegetables instead of meat, would reduce the demand of phosphorus between 20 and 45%, according to Cordell et al. (2009). Other solutions include the recovering of the use of manure in more rural and less-technological areas and promoting the composting of food waste in households, factories and commercial establishments. Finally, a waste from wastewater treatment plants, called struvite (magnesium ammonium phosphate) could help to fertilize the fields in an effectively and cleanly way.

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Struvite ore, like the one from the image, is obtained spontaneously in sewage treatment plants. Although it causes obstruction problems in the water treatment plant pipes due to its crystallization, it could be used as a clean fertilization system that would provide phosphorus, nitrogen and magnesium. Source: Creative Commons.

The madness begun at the beginning of the 20th century with the exploitation of the phosphoric rock to produce food in great quantity is almost over, and this requires us to adapt our crops and, perhaps, our way of life, to a future that will have to drink a lot of the proceedings carried out in the past. There is a need for a change of mentality, centered on a reduction of the world population and on a major sustainability of natural resources, if we really want to guarantee a world where no one is hungry.

REFERENCES

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