Why do we need phosphorus

How can it help to keep the world fed

Original Photo [Deposit Photos]

In the worst-case sce­nario, avail­able sup­plies of phos­pho­rus on Earth will run out in 50 years. It won’t dis­ap­pear com­plete­ly, of course, but we will no longer be able to mine it in the same way.

Why do we need phos­pho­rus for any­way?

Phos­pho­rus is present in DNA, so with­out it life on Earth (in the forms we know) is im­pos­si­ble. Ad­di­tion­al­ly, it is part of ATP – adeno­sine triphos­phate – a com­pound which con­tains two high-en­er­gy bonds, and serves as an en­er­gy source for many en­er­gy-in­ten­sive bio­chem­i­cal and phys­i­o­log­i­cal pro­cess­es in the body. Ad­di­tion­al­ly, phos­pho­rus as­sists the growth and re­cov­ery of the body.

In agri­cul­ture, phos­pho­rus is used wide­ly in fer­til­iz­ers and fod­der ad­di­tives. So, we de­pend on phos­pho­rus to keep the world fed.

In the first half of the 19th cen­tu­ry, the Swiss his­to­ri­an and po­lit­i­cal sci­en­tist Jus­tus von Liebig pop­u­lar­ized the Law of the Min­i­mum for agri­cul­ture. Ac­cord­ing to this law, growth is lim­it­ed by the scarcest re­source. The hy­dro­gen, oxy­gen and car­bon that plants re­quire are eas­i­ly ob­tained from wa­ter and car­bon diox­ide. From the mo­ment that peo­ple learned to syn­the­size am­mo­nia, there has also been enough ni­tro­gen. So phos­pho­rus be­came the lim­it­ing fac­tor in agri­cul­ture.

Western Sahara [Flickr]

The lion’s share of the world pro­duc­tion of phos­pho­rus comes from the West­ern Sa­hara – a for­mer Span­ish colony which now be­longs to Mo­roc­co. These mines con­tain 70% of avail­able phos­pho­rus. At the same time, sci­en­tists warn that the time is ap­proach­ing when pro­duc­tion will not be able to keep up with peo­ple’s re­quire­ments.

How did this hap­pen?

In na­ture, phos­pho­rus is only en­coun­tered in a bond with oxy­gen, which forms phos­phate. In this form, it is also mined. Chemists can sep­a­rate the oxy­gen and ob­tain pure white phos­pho­rus, which glows in the dark. But it is so un­sta­ble that it im­me­di­ate­ly catch­es fire as soon as it comes into con­tact with air. Phos­phate eas­i­ly en­ters the soil and wa­ter and is ab­sorbed by liv­ing cells. If it comes into con­tact with cal­ci­um or iron, it cre­ates high­ly in­sol­u­ble salts.

Human remains [Deposit Photos]

In the past, the fer­til­iz­er used in farm­ing was made of bones dug up in old bat­tle­fields, ap­prox­i­mate­ly half of which con­sist­ed of hy­drox­ya­p­atite, a min­er­al con­tain­ing phos­pho­rus – Ca₁₀(PO₄)₆(OH)₂. Guano (large heaps of bird dung) also con­tains a lot of phos­pho­rus, and was also used in agri­cul­ture. But these re­sources soon ran out, and peo­ple’s grow­ing needs re­quired new meth­ods to ob­tain phos­pho­rus. It be­gan to be mined.

But there are also prob­lems with these meth­ods. Phos­phates are eas­i­ly washed out of soil by ground wa­ters, and phos­phates from mines end up in the ocean. They set­tle on the ocean floor in the form of cal­ci­um phos­phates, or are ab­sorbed by sea crea­tures, and af­ter the crea­tures die these phos­phates also set­tle on the ocean floor. In any case, they be­come in­ac­ces­si­ble for us.

Underwater treasures [Deposit Photos]

In­evitable loss­es

Ev­ery­thing is com­pli­cat­ed by the fact that only 1 in ev­ery 5 kilo­grams of phos­pho­rus is ab­sorbed by the plants which we try to fer­til­ize. It is par­tial­ly washed away by ground wa­ters, and par­tial­ly bonds with cal­ci­um and iron in the soil. And al­though the roots of some plants are ca­pa­ble of ex­tract­ing phos­pho­rus from these bonds, they can­not ex­tract all of it. Ad­di­tion­al­ly, agri­cul­tur­al lands are de­prived of phos­pho­rus dur­ing har­vest time.

In the soil of vir­gin ecosys­tems – forests and wild grass­lands – the ma­jor­i­ty of phos­pho­rus is present in the form of or­gan­ic com­pounds. In­or­gan­ic phos­phates ab­sorbed by an­i­mals, plants and micro­organ­isms are re­tained in cells in the form of or­gan­ic sub­stances: phos­pho­lipids, phy­tate and oth­er com­pounds con­tain­ing phos­pho­rus, and af­ter the death of the or­gan­ism, they re­turn to the soil. This fine­ly-tuned sys­tem formed over mil­lions of years. And its sta­bil­i­ty de­pends on the num­ber and ac­tiv­i­ty of or­gan­isms par­tic­i­pat­ing in the process. In agri­cul­ture, in or­der to main­tain an abun­dance of mi­crobes in the soil that are ca­pa­ble of re­tain­ing phos­pho­rus, fields are fer­til­ized with ma­nure.


A dung bee­tle

But live­stock breed­ing – the only source for the re­quired quan­ti­ty of ma­nure – re­quires an enor­mous amount of phos­pho­rus it­self. Phos­pho­rus com­pounds take part in all the pro­cess­es in­volv­ing the an­i­mals’ growth. So the an­i­mals’ ra­tion is ar­ti­fi­cial­ly en­riched with it. It’s a vi­cious cy­cle of phos­pho­rus deficit!


A cow

Peo­ple also waste a lot of phos­pho­rus. Most of it, even when it is present in our food, is flushed down the drain. There are tech­nolo­gies for ex­tract­ing it from waste wa­ter, but they are cur­rent­ly too ex­pen­sive to be used in prac­tice.

Soil [Deposit Photos]

We con­stant­ly scat­ter phos­pho­rus around us, and it set­tles on the ocean floor, al­though this is not our fault. At the same time, we should pay more at­ten­tion to micro­organ­isms liv­ing in soil, and the role that they play in pre­serv­ing phos­pho­rus. Oth­er­wise our world will no longer be able to feed it­self at an ac­cept­able cost.


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