Peak phosphorus

A graph showing world phosphate rock production vs. year determined by the U.S. Geological Survey.

Peak phosphorus is the point in time at which the maximum global phosphorus production rate is reached. Phosphorus is a scarce finite resource on earth and due to its non-gaseous environmental cycle has resulted in alternative means other than mining being unavailable. According to some researchers, Earth's phosphorus reserves are expected to be completely depleted in 50–100 years and peak phosphorus to be reached in approximately 2030. Whereas in stark contrast the International Fertilizer Development Center in a 2010 report estimates that global phosphate rock resources will last for several hundred years. The predominant source of phosphorus comes in the form of phosphate rock and in the past guano.

Estimates of World Phosphate Reserves

The accurate determination of peak phosphorus is dependent on knowing the total world's phosphate reserves and the future demand for rock phosphate. Although many estimates for when peak phosphorus will occur have been made, many of them are marred by inaccurate knowledge of the quantity of world phosphate reserves. This is largely in part due to distrust in phosphate mines reports of total reserves, with the expectation that these values will be inflated to protect their business interests. The USGS, which obtains its figures from foreign governments, estimates that phosphorus reserves worldwide are 65 billion tons of which 15 billion tons is mineable, while world mining production in 2010 was 176 million tons. (Reserve figures refer to the amount in deposits recoverable at current market prices with present technology; phosphorus comprises 0.1% by mass of the Earth's 3 * 10¹⁹ ton crust, quadrillions of tons in total but at predominantly lower concentration than the most inexpensive deposits). These reserve figures, although widely used for predicting future peak phosphorus, have raised concern as to their accuracy due to the fact that they aren't independently verified by the USGS. The depletion of phosphorus is more relevant to our world today than the depletion of oil is. Phosphorus is a major component in fertilizer, without which fertilizer will be rendered useless. Without fertilizer, two thirds of the worlds population will starve because the Earth cannot support our demands for food. Also, there is no alternative to phosphorus, no synthetic way of creating it. Without new sources for high quality mineable phosphorus agriculture will face major problems within the next 50-100 years.

Exhaustion of Guano Reserves

In the early 1800s Alexander von Humboldt introduced guano as a source of agricultural fertilizer to Europe after having discovered it on islands off the coast of South America. It has been reported that at the time of its discovery that the guano on some islands was over 100 feet deep. The guano had previously been used by the Mochian people as a source of fertilizer by mining it and transporting it back to Peru by boat. International commerce in guano didn't start until after 1840. By the start of the 20th century guano had been nearly completely depleted and was eventually overtaken with the discovery of superphosphate.

Phosphorus Conservation and Recycling

In an effort to postpone the onset of peak phosphorus several methods of reducing and reusing phosphorus are in practice. Reducing agricultural runoff and soil erosion can slow the frequency with which farmers have to reapply phosphorus to their fields. Agricultural methods such as no-till farming, terracing, contour tilling, and the use of windbreaks have been shown to reduce the rate of phosphorus depletion from farmland. These methods are still dependent on a periodic application of phosphate rock to the soil and as such methods to recycle the lost phosphorus have also been proposed. The oldest method of recycling phosphorus is through the use of animal and human manures. Via this method, phosphorus in the foods consumed are excreted in the manures, which are subsequently collected and reapplied to the fields. Although this method has maintained civilizations for centuries it is unable to produce the vastly higher yields that modern phosphate rock based agriculture can generate. Despite that, its still the most efficient method of recycling used phosphorus and returning it to the soil. Alternative and far less efficient methods of recycling phosphorus have also been proposed. This includes the extraction of phosphorus rich materials such as struvite from waste processing plants.

The Soil Association, the UK organic agriculture certification and pressure group, issued a report in 2010 "A Rock and a Hard Place" encouraging more recycling of phosphorus. One potential solution to the shortage of phosphorus is greater recycling of human and animal wastes back into the environment.

References

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