Phosphorus and Us: We Have Too Little and Too Much

 Phosphorus is not a particularly rare element.  Its main characteristic is its critical importance to all life forms on Earth.  Dan Egan provides an interesting review of this material’s importance to us in The Devil's Element: Phosphorus and a World Out of Balance.  Phosphorus received that appellation when separation into the elemental state was first attained, and it was discovered that the metal would emit light when exposed to the atmosphere and would burst into flame at moderate temperatures.  Egan suggests the label is still appropriate because it is so critically important for life processes yet can be disastrous if too much is found in the wrong places.

“Phosphorus is essential for plant growth, and that makes it essential to us, but the element is important beyond helping to grow our food.  Phosphorus helps turn the meals we eat into the chemical energy that moves our muscles.  Phosphorus is also crucial to our physical structure, in the biggest ways and in the smallest.  Our bones and teeth are made with phosphorus.  Phosphorus is also in our DNA.  In fact, it is our DNA.  The rails of the famous twisting helices that form the genetic blueprints that bring to life every single cell on the planet are made of phosphorus.  From the corn we grow, to the animals that eat it, to the people who eat those animals, phosphorus is critical every step of the way.”

“No phosphorus, no life on Earth.”

Over the eons when the Earth cooled and settled into land and water regions, the oceans would accumulate traces of phosphorus as they interacted with rock structures.  The first life forms would be based on the chemistry of phosphorus compounds and would become, in effect, little factories for accumulating the element.  A phosphorus cycle would form where a lifeform bearing the element could be eaten by another lifeform and its phosphorus would be passed on, or it could die and decompose with its phosphorus either disbursed locally or settle down to the ocean floor where it would accumulate and form a rocky sediment.  Eventually, geological processes will move these sedimentary structures around and some will be uplifted and become the mineable sources of phosphorus we depend on today. 

There is a land phosphorus cycle that occurs more quickly, one that was broken when humans became more numerous.  Land plants would get their needed phosphorus from the soil and when they died, return it to the soil.  Some plants would be eaten by animals who would return consumed phosphorus to the soil by defecation and urination, while similarly depositing their supply back to the soil when dead and decomposed.  This cycle became broken when humans began to control the land and raised food that would be transported elsewhere for consumption.  Early farmers soon discovered that their land stopped producing after a short period unless they found ways to revitalize it.  Simple observations taught them that manure from animals could fertilize their land, and therefore, their own manure could perform the same function.  There are limitations to this process, but small plots of land have been treated in this way up until current times.

As agriculture became bigger and cities and towns were formed with masses of people, collecting human waste became unacceptable.  Some other form of phosphorus had to be found to keep crops producing.  Grinding bones from animals was tried for a time while collecting bird excrement (guano) from ocean islands was also tried, but for both sources demand soon swamped supply.  Methods for the artificial production of fertilizers were developed early in the twentieth century.  The key ingredients of potassium and nitrogen were plentiful, while the other key ingredient of phosphorus would be obtained from those uplifted sedimentary deposits from ocean floors wherever they could be found.

This use of artificial fertilizer has allowed us to produce enough food for all the people on Earth, even as that number has grown too large to be sustainable for other reasons.  However, there have been serious downsides to this approach.   Much of the large amounts of fertilizer we produce ends up seeping into or running off into various water systems.  Phosphorus will accelerate growth of vegetation whether we want it to or not.

“…much of today’s rock-based fertilizer spread by farmers gets washed off croplands before it can be taken up by plant roots.  So instead of making bumper crops of food, it tumbles into our streams, rivers, and lakes where it then fertilizes bumper crops of blue-green algae.”

Farmers are not the only ones dumping fertilizer into the waterways.

“And much of that phosphorus that does make its way to the food on our dinner tables then makes its way, via sewer lines, into our water instead of back onto croplands.”

“…hitching our existence to mined phosphorus in this fashion carries its own Faustian burden.  In exchange for breaking the natural throttle that limited how many humans Earth could sustain, we are polluting fresh waters with phosphorus fertilizer to the point where those waters are increasingly prone to be too fouled to swim in, to fish upon, and to drink from.  We are soiling our own garden.”

Some of the algae produced are not only unpleasant, they’re also poisonous.  Massive algae plumes are followed by decomposition that sucks up the oxygen from the water creating dead zones.  Egan devotes a good fraction of his book to the trouble that has been caused by the overabundance of phosphorus in our waterways.  Here we will focus more on the supply issues.

“Mining industry officials maintain that there are enough reserves to last another 350 years while…some phosphorus experts contend that dangerously destabilizing shortages could come in a matter of decades.  But even the rosy 350-year horizon does not buy humanity much time.”

“…we are blowing through Earth’s accessible deposits at such a pace that…some scientists now fear that we could hit ‘peak phosphorus’ in just a matter of decades, at which point we risk declining mining yields—and chronic food scarcity.”

“Florida miners are on pace to run out of available rock in as few as thirty years, at which point the United States is at risk of becoming dependent on other countries to sustain its agricultural system.”

“Whether those countries share an interest in maintaining our nutritional security is another question.  Roughly 70 to 80 percent of the globe’s remaining phosphorus reserves are located in Morocco and the Western Sahara territory that Morocco has occupied—sometimes violently—since the 1970s.  For one country, essentially one guy—the King of Morocco—to control so much of something every soul on the planet so desperately needs is a recipe for global instability, or worse.”

Even if we manage to draw down our supply of phosphorus peacefully, it will run out on a timescale that demands conservation measures that begin soon.  We must figure out ways to use it much more efficiently and keep its utilization from polluting our waterways.  We must all begin to conserve phosphorus supplies.  Egan tells us we must realize that what we consider waste must become a valued resource.  Urine and manure, including our own, must be processed to recover phosphorus.  If we wish to preserve the civilization we have grown accustomed to, even cadavers must be processed in an appropriate fashion.