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Our ability to provide enough food to feed the human population is dependent on the availability of phosphorus.

By Greg Seaman Posted Jan 28, 2009

While the term “peak oil” has become a familiar term in the lexicon of sustainability, the notion of “peak phosphorus” may ultimately be a concern of greater consequence.

Phosphorus is an essential nutrient required by plants that is primarily responsible for healthy root development and fruit and flower production. It is one of the three principal ingredients (nitrogen, phosphorus, and potassium ) of fertilizers used for growing food around the world. Phosphorus is essential to plant life, and there is no substitute for it in agriculture. The supply of available phosphorus limits the size of the population possible in an ecosystem.

Phosphorus is a non-renewable resource. Estimates of global reserves of phosphate suggest that supplies may last from 50 – 130 years. However, problems with resource supply begin when production reaches its peak, and long before supplies actually run out. Physicist Patrick Déry estimates that U.S. “peak phosphorus” occurred in 1988 and for the world in 1989. Signs of volatility have recently appeared in phosphorus markets, and may already be contributing to higher food prices. We are approaching a threshold where world agricultural requirements may begin to outpace available supplies of phosphorus.

Global Supply of Phosphorus

Most phosphorus is obtained from mining phosphate rock, which occurs as marine sedimentary phosphate deposits, and in igneous rocks that are rich in phosphate minerals. Crude rock phosphate is commonly used in organic farming, whereas chemically treated forms such as superphosphate, triple superphosphate, or ammonium phosphates are used in non-organic farming.

The largest sedimentary phosphate rock deposits are found in northern Africa, China, the Middle East, and the United States. Significant igneous occurrences are found in Brazil, Canada, Russia, and South Africa. Large sedementary phosphate resources have also been identified on the continental shelves and on seamounts in the Atlantic Ocean and the Pacific Ocean, but cannot be recovered economically with current technology.

According to the US Geological Survey (2007), U.S. phosphate rock production and use dropped to 40-year lows in 2006 owing to a combination of mine and fertilizer plant closures and lower export sales of phosphate fertilizers. China has surpassed the United States as the largest phosphate rock producer. It is likely that production capacity will continue to decline gradually owing to depletion of reserves in Florida and increased global competition in the fertilizer industry, which may result in lower domestic phosphoric acid production. Three new mines are planned to open in the next decade in Florida, but only as replacements for existing mines.

Most of the world’s farms do not have or do not receive adequate amounts of phosphate. Feeding the world’s increasing population will accelerate the rate of depletion of phosphate reserves.

Recycling Phosphorus

Current scientific research has focused on ways to more efficiently apply phosphate fertilizers, and on ways to recover and recycle phosphorus before it exits the waste stream.

Agriculture, the greatest user of phosphates, is largely inefficient in its management of phosphorus. Adopting methods which apply fertilizers more precisely will help conserve supplies while reducing the nutrient pollution from fertilizer runoff on downstream watersheds.

And although phosphorus is a non-renewable resource, it is recyclable. Phosphorus can be extracted and reused from human and animal waste. Sweden and Germany are leading the way on promoting phosphorus recycling. Sweden for example has mandated that 60% of phosphorus must be recovered at its wastewater treatment plants by 2015 and the UK is also promoting phosphorus recycling. Every municipal wastewater treatment plant is potentially a ‘phosphorus mine’. Agricultural and industrial waste streams are also potential ‘mines’. New ‘no-mix’ toilets are also being tested in Germany which separate waste ‘at the source’ for reclaiming phosphorus. Today, around one quarter of the phosphates in municipal sewage in Europe are already effectively recycled as fertilizer for agriculture.

Alternative local sources of phosphorus:

Small-scale farmers, homesteaders and backyard gardeners who are concerned about future availability of phosphorus can lay in a supply of rock phosphate for future use, since it stores well if kept dry. However, some gardeners in the US and Canada have reported difficulty in finding local sources of rock phosphate. Also, stocking up on a non-renewable resource does little to help alleviate shortages. Organic gardeners and farmers should also look to alternative sources of phosphorus where possible.

Alternative sources of phosphorus include:

  • Compost – Food wastes contain high levels of phosphorus which can be accessed through composting. In addition, compost supplies many other nutrients that will keep your plants healthy.
  • Bonemeal – Available at most garden centers, bonemeal is ground bone in powdery form. Bone meal can contain anywhere from 20 to 30 percent phosphorus. Follow package directions for applying the correct amount, and till the bonemeal just under the soil surface or, if you use the no-till method, sprinke the bonemeal on the soil and cover with mulch. Mice can be attracted to exposed bonemeal.
  • Urine diversion – Small garden plots can benefit from human urine as a source of phosphorus. A small pee-pot can be located in a discreet part of the garden; dilute with equal part water and pour directly on garden beds. Urine is high in nitrogen, so withold this from fully grown plants which are entering their fruiting stage. Alternatively, the mix can be applied to a fallow bed, or one planted in a green manure. It is not advisable to use this practice in market gardens.

As for large scale alternative sources, the phosphorus deposits on the ocean floor may one day be recovered when a profitable method of deep ocean mining is developed. Deep-sea exploration of the world’s oceans has revealed that there are large deposits of phosphates on the continental shelf and on seamounts in the Atlantic and Pacific Oceans. Recovering these deposits, however, is still too expensive, so they remain untouched for now.

References:
Peak Phosphorus (PDF), by Patrick Déry and Bart Anderson (2007)
Introduction to Phosphorus recycling
Peak Phosphorus – Commence urine recycling …. by Paul O’Callaghan
Multiple documents on phosphates are available at the USGS’s Phosphate Rock Statistics and Information. Last updated 2007.

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  • Waste Management

    The alternative sources of phosphorus are really good ideas and I think these should be promoted a lot more via means of advertising on billboards, television, etc. If everyone could use these alternative ideas we could all make a difference in sorting the shortage problem out. It is estimated that in about 345 years time it will have completely ran out. Although this figure may not seem so scary for us, we need to make changes now so that in the future people won't be stuck with the problem of having none left. Having a compost maker is a fantastic idea, it not only is a great way to grow your vegetables but also a way of having less garbage waste.

  • http://www.le-jardinier.fr/ Jimmy

    Well it looks like we are overexploiting everything…Even phosphorus ! But at least for backyard gardeners there are alternatives like the compost. Only the massive grow industry will suffer about this, and we have to hope in we don’t rely upon them for food in the near future (also it would be better for food quality, anyway.)

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