Peak oil has made us aware that many of the resources on which civilization depends are limited.
M. King Hubbert, a geophysicist for Shell Oil, found that oil production over time followed a curve that was roughly bell-shaped. He correctly predicted that oil production in the lower 48 states would peak in 1970. Other analysts following Hubbert's methods are predicting a peak in oil production early this century.
The depletion analysis pioneered by Hubbert can be applied to other non-renewable resources. Analysts have looked at peak production for resouces such as natural gas, coal and uranium.
In this paper, Patrick Déry applies Hubbert's methods to a very special non-renewable resource - phosphorus - a nutrient essential for agriculture.
In the literature, estimates before we "run out" of phosphorus range from 50 to 130 years. This date is conveniently far enough in the future so that immediate action does not seem necessary. However, as we know from peak oil analysis, trouble begins not when we "run out" of a resource, but when production peaks. From that point onward, the resource becomes more difficult to extract and more expensive.
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In some ways, the problem of peak phosphorus is more difficult than peak oil. Energy sources other than oil are available, though they all have their own shortcomings. In addition, the sun provides a steady input of energy.
Unlike fossil fuels, phosphorus can be recycled. However if we waste phosphorus, we cannot replace it by any other source. Currently we are running through the limited supplies of concentrated phosphates. Phosphate fertilizer is often applied carelessly, leading to waste and pollution. Food from agriculture goes to consumers and animals, who excrete most of the phosphorus. The phosphorus in sewage mainly goes to sea or is otherwise dispersed.
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