Phosphorus shortage: How to safeguard the agricultural system’s future.

The Dirty but Necessary Way to Feed 9 Billion People

The citizen’s guide to the future.
Dec. 25 2013 11:41 PM

The Dirty Way to Feed 9 Billion People

The solution to a major agricultural problem is a little gross, but it’s necessary.

Tasseled out corn crop, northwest Iowa, July 2013.
Tasseled out corn crop, northwest Iowa, July 2013.

Courtesy Don Graham/Flickr

Future 1: It's a world with intermittent food riots stemming from rising and unpredictable fertilizer prices, declining crop yields, and collapsing farm profits. Toxic algal blooms are spreading in the world's lakes, and the Gulf of Mexico dead zone is the size of Michigan. Trade ambassadors of the United States and Europe pay regular visits to Morocco, negotiating arms deals and special trade relations in the hopes of keeping the fertilizer coming. It's a crappy world getting crappier.

Future 2: It's a world with abundant production from rich green fields fed by a resilient and reliable fertilizer supply that is recycled regionally and locally by a new industrial sector built on energy and nutrient recapture from food waste, manure, and sewage. Cities are now part of the farm. Low, stable fertilizer prices mean enhanced food security for all. Lakes and rivers are clean and supply abundant fresh drinking water, while dead zones have recovered and coastal oceans support sustainable fisheries for a rich source of protein. It's a crappy world getting better!

These two futures hinge on what happens during the coming decades as supplies of high-quality phosphate rock become so depleted that it no longer pays to dig them up. Why’s phosphate so important?  Because it’s a bedrock of modern agriculture.


First some facts about phosphorus (P). P is a chemical element and exists almost entirely in the form of phosphate (PO4 3-). Since P is a chemical element, we can't make any more, unless you have a supernova explosion under your control. Likewise, we can't destroy it. For millennia, geology has allowed phosphate to slowly accumulate in ancient seabed formations in just a few lucky locations around the world. P is essential to all life (it's literally in our DNA), including plants—such as agricultural crops. So, without phosphate, the breadbasket of America would be empty.

This brings us to where we are now. The Green Revolution, the major mid-20th-century expansion of global food production, relies in large part on fertilizer, to the tune of approximately 20 million metric tons of P in fertilizers applied in 2012 worldwide. Without it, agricultural productivity would have to get by with phosphorus that gets into soil by natural weathering of P from Earth’s rocks, which would only yield about 10 percent of what’s currently used—and would be wholly incapable of supporting our current population, much less the 2 billion to 4 billion additional humans expected for 2050.

Where does all this phosphorus for fertilizer come from? From mining operations focused mostly on ancient P-rich geological deposits that are concentrated in just a handful of countries, with Morocco having the lion’s share—about 75 percent at last report. China, in second place, has only 5.5 percent, and the United States trails in seventh with about 2 percent. These reserve estimates, however, can change surprisingly quickly. For example, Morocco’s estimate increased roughly tenfold essentially overnight in 2010, when an economic geologist took into account information from an old report that had been overlooked for more than two decades. So, while short-term concerns about the dreaded “peak phosphorus” have faded somewhat, we still have a P supply dominated by just a few global players. U.S. phosphate fertilizer production has been on a steady decline since about 1940, as prime sources have been depleted and environmental concerns constrain remaining operations. Extrapolating this trend, the United States will become entirely reliant on imports within roughly three or four decades.

Globally, phosphate is on something of a conveyor belt: It’s removed from rich geologic deposits and then gets dispersed widely around the world. Today P is accumulating in overfertilized agricultural soils in Europe and the United States or is running off from fields as erosion and leaching. The P that is captured in crops ends up largely in forms that are less than appetizing. Livestock eat it from P-rich feeds and then something becomes piled high and deep and it contains a lot of P. Nontrivial amounts of P also are in the food that we waste—and in the food that we eat and turn into our own waste.

This global P conveyor belt dumps much of its load into rivers, lakes, and coastal oceans where it makes a mess—algal blooms (including toxic forms) and dead zones. In one shocking example from 2007, nutrient runoff into China’s Lake Taihu combined with an unusual warm spell to produce such a massive bloom of toxic cyanobacteria that the city of Wuxi had to shut down its drinking-water supply and truck in bottled water for well over a million people for more than a week. Meanwhile, the fertilizer-fed dead zone in the Gulf of Mexico varies in sizes that are compared to various Northeastern U.S. states, Connecticut in one year, New Jersey the next.

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