Wasteful use of phosphorus in agriculture is a key concern in UNEP Year Book 2011

February 21st, 2011 by United Nations Environment Programme

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The UNEP Year Book 2011 highlights the use of phosphorus, demand for which has rocketed during the 20th century, in part because of the heated debate over whether or not finite reserves of phosphate rock will soon run out.

Massive amounts of phosphorus, a valuable fertilizer needed to feed a growing global population, are being lost to the oceans as result of inefficiencies in farming and a failure to recycle wastewater.

Phosphorus pollution, along with other uncontrolled discharges, such as nitrogen and sewage, are linked with a rise in algal blooms which in turn harm water quality, poison fish stocks and undermine coastal tourism.

In the United States alone, the costs are estimated to be running at over US$2 billion a year, indicating that globally and annually the damage may run into the tens of billion of dollars.

An estimated 35 countries produce phosphate rock with the top ten countries having the highest reserves being Algeria, China, Israel, Jordan, Russia, South Africa, Syria and the United States.

New phosphate mines have been commissioned in countries such as Australia, Peru and Saudi Arabia and countries and companies are looking further afield, including on the seabed off the coast of Namibia.

Some researchers are suggesting that the consumption of phosphorus globally is in the medium to long term unsustainable and that peak production, with a decline afterwards, could occur in the 21st century.

Others disagree. The International Fertilizer Development Centre recently revised upwards estimates of reserves from around 16 billion tonnes to 60 billion tonnes—at current production rates, these could last 300 to 400 years. The United States Geological Survey also recently adjusted their estimates to 65 billion tonnes. Nevertheless, proponents of the peak phosphorus theory argue that even if the timeline may vary, the fundamental issue, that the supply of cheap and easily accessible phosphorus is ultimately limited, will not change.

The Year Book calls for a global phosphorus assessment to more precisely map phosphorus flows in the environment and predict levels of economically viable reserves.

According to the Year Book, the global use of fertilizers that contain phosphorus, nitrogen and potassium increased by 600 per cent between 1950 and 2000.

It adds that population growth in developing countries and increased levels of dairy and meat in the global diet are likely to increase fertilizer use further.

“While there are commercially exploitable amounts of phosphate rock in several countries, those with no domestic reserves could be particularly vulnerable in the case of global shortfalls,” the Year Book notes.

Further research is also needed on the way phosphorus travels through the environment in order to maximize its use in agriculture and livestock production and cut wastage while reducing environmental impacts including on rivers and oceans.

  • Currently humans consume—via food—around only a fifth of the phosphorus mined with the rest retained in soils or released to the aquatic environment.
  • Over the last 50 years concentrations of phosphorus in freshwaters and land has grown by at least 75 per cent.
  • The estimated flow of phosphorus to the marine environment from the land is now running at around 22 million tonnes a year.

The Year Book points to the enormous opportunity of recycling wastewater: in the mega-cities of the developing world up to 70 per cent of this water—laden with nutrients and fertilizers such as phosphorus—is discharged untreated into rivers and coastal areas.

  • Sweden, for example, aims to recycle 60 per cent of the phosphorus in municipal wastewater by 2015.

Other measures to reduce discharges include cutting erosion and the loss of topsoil where large quantities of phosphorus are associated with soil particles and excess fertilizers are stored after application.

  • In Africa soil losses are running at close to 0.50 tonnes per hectare a year and in Asia it is even higher, at almost 1.70 tonnes per hectare per year.

Land management measures include contour ploughing; contour planting of hedgerows on steep slopes and applying mulches and planting cover crops and other vegetation on land.

Boosting recycling rates at phosphate rock mines can also assist in conserving stocks and reducing discharges to local water systems.

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