Phosphorus: Running low of an essential fertilizer?
Your body contains about a kilogram of phosphorus, in your DNA, your bones, indeed, in virtually every cell. Plants are equally reliant on phosphorus, which along with nitrogen and potassium is one of the top three fertilizing elements.
A shortage of phosphorus in the soil, a problem that is particularly acute in Africa and Australia, is a major reason for low farm yields.
Phosphorus fertilizer comes from phosphate rock, of which 142 million tons was mined worldwide in 2006. Due to the soaring demand for phosphorus fertilizer, the price of one ton of diammonium phosphate (a fertilizer that also contains nitrogen) "jumped to $1,102 a ton from $393 a ton in the last year," according to an April, 2008 report.
Is the soaring price a temporary blip, or a sign that phosphorus rock is getting scarce? Given agriculture's reliance on phosphorus, we were alarmed to read warnings of an impending phosphorus crisis from a research group headed by Stuart White, director of the Institute for Sustainable Futures at the University of Technology in Sydney, Australia.
Losing the curve
The warnings of "peak phosphorus" echo the arguments over "peak oil," which maintain that the important date in resource extraction is not when the resource is totally exhausted, but when its production peaks after about half of the resource is used up. Because production must (by definition) drop after the peak, prices must rise unless demand falls. Over the last 30 years, peak oil has been miraculously transfigured from heresy to conventional wisdom. Some experts say we are now close to the peak, and that the era of tightened supply and unceasing demand will lead to yet more international tension as nations scramble to grab the remaining oil.
To determine when peak phosphorus could occur, White and his Ph.D. student Dana Cordell compared the total amount of phosphate rock extracted since 1900 to the estimates of how much can reasonably be recovered, and projected a peak in 2034 -- just a quarter-century from now.
Graph: Phosphorus Futures
We phoned Stephen Jasinski, the U.S. Geological Survey's expert on phosphate supplies, who said known phosphate reserves will last at least 200 years at the current rate of consumption, and that "there are a lot of other resources that could be tapped, in national forests or offshore, if it came to that." The recent price rises, he added, reflect short-term scarcity. "World production capacity has not increased as fast as demand, but several projects are scheduled to come on line in the next three or four years, which would increase production and hopefully reduce the price."
None of this sounded like an emergency, but in the long term, phosphorus consumption must continue rising to feed a growing population that wants to eat more meat and burn more ethanol. And thus Jasinski acknowledges that the current rate of consumption is not a reliable indicator of how long phosphate supplies will last.
Furthermore, the peak analysis focuses on when production starts to decline, not when the last ton of phosphorus fertilizer is produced. So are Cordell and White on track in their forecast of peak phosphorus? Yes, Jasinski says. "The peak could happen around 2034; it seems possible, seems reasonable that we could see a decline, a drop-off, based on the reserve figures."
As the oil market shows, scarce resources demand high prices, and producers will begin to dig up phosphate deposits that are more expensive to process, much as oil companies have shifted operations to deep water and the Arctic. But peak phosphorus may be a bigger problem than peak oil, since it's possible to shift to another energy source, while phosphorus cannot be manufactured.
And so Jasinski says it makes sense to examine exhaustion while a lot of phosphate remains in the ground. "There is some concern, with a growing population, with its need for food, increased use of fertilizer, and with biofuels coming on, about having enough phosphate for fertilizer in the future, but we're not going to run out in 100 years. We could be out in 200 to 300 years, so it is probably good to look at [recycling] in the future."
A win-win solution
Another phosphorus problem: Pollution
A second phosphorus phactor phocuses on phosphorus pollution, the phlip side of shortage. In both fresh- and salt-water, excess phosphorus can initiate choking blooms of plants and algae. The runoff of phosphorus -- along with nitrogen -- from farm fields is the major cause of the "dead zones" that afflict the Gulf of Mexico and hundreds of other coastal waters.
As Cordell points out, recycling some of the millions of tons of phosphorus that originate in fertilizer or sewage and move to the seas each year would address the twin problems of pollution and shortage. What is happening with phosphorus recycling?
· A urine-collecting toilet could be the first step in recycling phosphorus. Sweden plans to use these toilets to help meet its goal of recycling 60 percent of the phosphorus in sewage to farmland by 2015.
· Simple technologies that offer a two-fer solution to sanitation and farm fertility are suitable to places without sewage systems. Demonstration projects by the Ecosan movement in India, for example, recycle human waste into fertilizer while reducing the spread of disease. These recycling toilets gather the urine, compost the feces, and divert both wastes into high-phosphorus fertilizer, Cordell says. "Once the community and householders can see that people are producing fantastic banana trees [using the organic fertilizer], the yields are really high, it increases awareness and reduces the perception that waste is dangerous to use."
· Phosphorus can be removed from sewage treatment plants in a crystal called struvite. Collecting struvites can be a win-win tactic, because the crystals can clog pipes, but can be sold as fertilizer after collection, reducing the clogging problem. Sewage plants in the United States recycle to farm fields or forests 50 percent to 60 percent of the sludge ("biosolids") that remains after sewage undergoes biological fermentation. After tests for heavy metals and other pollutants, biosolids make an excellent soil conditioner and fertilizer, says Rufus Chaney, of the Agriculture Research Service at the U.S. Department of Agriculture. "Biosolids, like livestock manures, are valuable phosphorus fertilizers ... that can save $50 to $100 per acre per year compared to purchase of commercial phosphorus fertilizers, and more from the nitrogen fertilizer value."
· These nutrients are wasted when sludge is burned or buried in landfills. Sewage sludge recycling can also address the phosphorus pollution problem, Chaney adds. "With present goals of protecting surface waters from phosphorus runoff, all phosphorus sources need to be managed to prevent runoff... [but] only biosolids are well regulated to prevent phosphorus runoff."
Waste not, want not
Although peak phosphorus may be more remote than peak oil, this humble element is so critical to human survival that our question answers itself: Is it more sensible to reuse the maximum amount of phosphorus, or continue to mine the best deposits of phosphate rock as we dump billions of tons of phosphorus into rivers, lakes and oceans?
Although the date of peak phosphorus is impossible to predict, phosphate miners are already digging lower-grade deposits, Cordell says, which raises costs, uses more energy, and produces even bigger mountains of waste. As she and White wrote, "While the exact timing may be disputed, it is clear that already the quality of remaining phosphate rock reserves is decreasing and cheap fertilizers will be a thing of the past."
Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive