June 01, 2009
Phosphorus Depletion Problem In Late 21st Century?
In a pretty good article written for Scientific American David A. Vaccari says we might run out of phosphorus reserves late in the 21st century. Since phosphorus is one of the 3 key elements in NPK fertilizer exhaustion of phosphate mines would cause a big problem for food production.
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.”
I'm not worried about the N (Nitrogen) part of fertilizer. I expect we will find ways to generate enough energy to reduce N from the atmosphere and attach hydrogen to it. If we have enough energy we have enough ammonia.
The K (Potassium as potash) reserves look like they'll last longer as compared to phosphorus. So I'm not worried about that one. But I am concerned about the phosphorus. Maybe we will find some more big deposits and kick the problem into a future century. But we can't be sure that's the case.
There's an added benefit to treating the phosphorus problem as real: If we take steps to reduce phosphorus run-off (e.g. use no-till farming) then we also cut back on algae blooms that eat up all the oxygen and cause deade zones.
I think this may be FUD. The producers (in Bone Valley deposit of Florida) claim that they have about 300 years worth in Florida alone, but that the rock formation that they are mining extends all along the Atlantic sea coast. There is apparently no end in sight. What seems more accurate is that the costs may rise as new areas of the formation are mined. I also suspect that there are many, many more large deposits but there is no demand yet for exploration or development.
Phosphorus is an element. If it isn't leaving the earth (i.e. it isn't light enough to escape our atmosphere), and it isn't undergoing nuclear decay it is still here. With cheap enough energy it should be possible to find a way to put it back into it's elemental form.
your website is interesting, but there's no reference for the 300 year projection. Do you have a link?
The potential long term problem of phosphorus availability has been know for a long time. I recall seeing references to it from the early 20th century. Eventually, we'll probably need to mine it from much lower grade deposits. IIRC, its average crustal abundance is around .1% by mass.
Also, as I recall, much phosphorus that is applied to farmland is not washed away or removed in biomass (which can of course be recycled), but rather becomes less available in the soil by binding into less soluble forms. Over the long term, these less soluble forms will accumulate, if the soil is not being lost to erosion, and even if less available the total mass present will mean the plants have access to more of the element. Greatly slowing erosion is the important part anyway.
As you note, nitrogen and potassium are not problems. Effectively unlimited amounts of each are available, from air and from seawater respectively.
Aha! I found a reference for the 300 years claim:
"How Long Will Florida Phosphate Mining Go On?
For decades, it has been said that the phosphate in Florida could be mined for about another 25 years. Technological advances and market changes, however, have continually lengthened the expected life of phosphate mining, allowing mining of rock that wouldn’t have been mined in previous years.
The Hawthorne Formation, which contains much of the Florida phosphate deposits, covers much of the Atlantic Coastal Plain of the southeastern United States. In the heart of the Central Florida phosphate district, the Bone Valley Formation overlays the Hawthorn Formation. The two are separated by a limestone layer of varying thickness. It is the Bone Valley Formation that has produced the majority of mining activity in central Florida to date. The Hawthorne Formation is being mined in North Florida. It is also the Hawthorne Formation that is being mined in the southern extension of the central Florida phosphate district.
Florida phosphate reserves alone contain about 10 billion tons of soluble phosphate rock. Based on the current mining rate in Florida, this would last more than 300 years if economic and technological conditions allow."
Excuse me, I was looking at US demand. For world demand, it's about 300 years.
Paul, With a growing world population and rising living standards the consumption rate will grow and could easily double or more.
Reserve versus reserve base: Is that reserve base really all extractable?
Nick G, The current mining rate is key. If demand rises then it'll go faster. Also, US production is only 18% of world production.
Hawthorne Formation: How hard is it to extract from areas further up the coast?
Randall, these are good questions. OTOH, I have a hard time working up a lot of worry about somethat that appears to have such a large resource base (it appears that the USGS resource is understated, if the source I found is accurate, and the footnotes on the 2007 report is accurate:
"Large phosphate resources have been identified on the continental shelves and on seamounts in the Atlantic Ocean and the Pacific Ocean. High phosphate rock prices have renewed interest in exploiting offshore resources of Mexico and Namibia."
After all, consumption could go down, with improved farming practices and recycling - roughly half of US ag production goes to livestock - recycling their phosphorus shouldn't be that hard, in the grand scheme of things.
The USGS expert's email is on the report - we could just ask him directly...