We're all well aware of the impending shortages of oil and water. There is even a problem with worldwide lithium, given our interest in producing hybrid and electric vehicles. Well, it also turns out there is a looming problem with phosphorus.
This article from Scientific American, (digital subscription required for $40/year, or the issue is available for $8) details the major implications for all of us given our use of phosphorus.
As complex as the chemistry of life may be, the conditions for the vigorous growth of plants often boil down to three numbers, say, 19-12-5. Those are the percentages of nitrogen, phosphorus and potassium, prominently displayed on every package of fertilizer. In the 20th century the three nutrients enabled agriculture to increase its productivity and the world’s population to grow more than sixfold. But what is their source? We obtain nitrogen from the air, but we must mine phosphorus and potassium. The world has enough potassium to last several centuries. But phosphorus is a different story. Readily available global supplies may start running out by the end of this century. By then our population may have reached a peak that some say is beyond what the planet can sustainably feed.
Moreover, trouble may surface much sooner. As last year’s oil price swings have shown, markets can tighten long before a given resource is anywhere near its end. And reserves of phosphorus are even less evenly distributed than oil’s, raising additional supply concerns. The U.S. is the world’s second-largest producer of phosphorus (after China), at 19 percent of the total, but 65 percent of that amount comes from a single source: pit mines near Tampa, Fla., which may not last more than a few decades. Meanwhile nearly 40 percent of global reserves are controlled by a single country, Morocco, sometimes referred to as the "Saudi Arabia of phosphorus." Although Morocco is a stable, friendly nation, the imbalance makes phosphorus a geostrategic ticking time bomb.
In addition, fertilizers take an environmental toll. Modern agricultural practices have tripled the natural rate of phosphorus depletion from the land, and excessive runoff into waterways is feeding uncontrolled algal blooms and throwing aquatic ecosystems off-kilter. While little attention has been paid to it as compared with other elements such as carbon or nitrogen, phosphorus has become one of the most significant sustainability issues of our time.
So we have an adequate supply for now in the US, but that could be depleted in a few decades at which point we'll be largely dependent upon a small middle eastern country. Does this sound kind of like oil in the 50's and 60's?
The article goes on to state that one of the main culprits is how we use phosphorus. For millenia, phosphorus cycled through the system fairly efficiently. Animal and human waste was generally in the same field as the crops. That all changed during the 20th century as farming practices moved food consumption from its production. Now we simply go to the grocery store to buy our produce that may have been grown on the other side of the world.
Just to be clear, although the shortage is looming, we are not in any immediate danger. Worldwide reserves are still adequate for somewhere in the neighborhood of 50-100 years. This should give us enough time to deal with the problem, and there are solutions.
The standard approaches to conservation apply to phosphorus as well: reduce, recycle and reuse. We can reduce fertilizer usage through more efficient agricultural practices such as terracing and no-till farming to diminish erosion [see "No-Till: The Quiet Revolution," by David R. Huggins and John P. Reganold; Scientific American, July 2008]. The inedible biomass harvested with crops, such as stalks and stems, should be returned to the soil with its phosphorus, as should animal waste (including bones) from meat and dairy production, less than half of which is now used as fertilizer.
We will also have to treat our wastewater to recover phosphorus from solid waste. This task is difficult because residual biosolids are contaminated with many pollutants, especially heavy metals such as lead and cadmium, which leach from old pipes. Making agriculture sustainable over the long term begins with renewing our efforts to phase out toxic metals from our plumbing.
One other major problem that has to be corrected is that of agricultural runoff. Having worked in the environmental field for more than 2 decades, I've worked with the South Florida Water Management District on a lot of different projects involved with Everglades restoration. One of the main concerns is phosphorus runoff from nearby sugar farms. In pristine condition, the Everglades should have less than 10 parts per billion (ppb) of phosphorus, and the less the better. 8 ppb or even 6 ppb is the goal.
The same thing occurs in many areas, and if the runoff hits a river or stream, it can eventually reach a large lake or ocean, where recovery becomes very difficult if not impossible. How exactly do you mine sediment 2000 feet below the surface for trace amounts of phosphorus?