Phosphate Depletion
Unfortunately, the resources that are currently depleting are not limited to oil, gas, fresh water or the atmosphere's ability to accommodate greenhouse gases. A number of resources are reaching critical levels. Among those of most relevance to the food system are phosphate and potassium, which together with nitrate are the three key "macronutrients" used in agriculture.
Life's Bottleneck
Jim Conrad at Backyard Nature asks:
...Which of the above mineral elements do organisms stand the greatest chance of running out of?
The answer is: Phosphorus.
In fact, Isaac Asimov, an important science writer, has defined phosphorus as "life's bottleneck." This is true even though phosphorus is by no means the rarest mineral element. If you have a miniscule amount of something but only need a tiny, tiny bit of it, then that's less critical than if you have a fair amount of something, but you need a lot of it...
Asimov noticed that some mineral elements are more common in organism bodies than in the surrounding environment. Obviously that organism has needed to concentrate that element in itself. The degree of concentration of that element in the organism's body, then, becomes a good indication of these two things:
- * how much organisms need that element
- * how available it is in the environment
Asimov noted that phosphorus composes about 0.12% of an average soil, yet a much greater percentage of an alfalfa plant's body, about 0.7%, is phosphorus. Therefore, the "concentration factor" for phosphorus is about 5.8 (0.7/0.12).
No other mineral element even comes close to having a concentration factor as great as phosphorus's. The closest is sulfur with 2.0, then chlorine with 1.5. All the rest have less than a factor of 1.
Therefore, if there are more and more organisms needing mineral elements, or if the living ecosystem is more and more depleted of its resources, which mineral element will come into short supply first?
Phosphorus.
Phosphate Depletion
EcoSanRes is part of the Stockholm Environment Institute. In a paper on phosphate depletion (April 2005), they note that:
Phosphorus is a nutrient essential to all living organisms, and thus, it is essential in food production for humans. Although it is the eleventh most abundant element on earth, phosphorus never occurs in its pure form and is always bonded with other elements forming other compounds, such as phosphate rock. More importantly, much of the phosphorus in soil is not available to plants, thus requiring nutrient additions to produce crops. This non-renewable resource is being mined at an increasing rate to meet the demand for artificial fertilizers so heavily relied on in agriculture. In all, chemical fertilizers account for 80% of phosphates used globally, with the other 20% divided between detergents, animal feed and special applications (such as fire retardants).
More than 30 countries produce phosphate rock for commercial purposes, with the top 12 countries supplying 91% of all phosphorus. China, Morocco and the United States alone currently produce almost two-thirds of global phosphate.
...Estimates on the remaining amount of phosphorus vary, as do projections about how long it will take to deplete the irreplaceable resource entirely. Figures range from 60-130 years (Steen, 1998) and 60-90 years (Tiessen, 1995), at current market prices with diverse assumptions about the rate of production and demand, but all sources agree that continued phosphorus production will decline in quality and increase in cost. The relatively inexpensive phosphorus we use today will likely cease to exist within 50 years (see Figure 1).
(Thanks to the Energy Bulletin for their summary.)
The peak oil community has spread awareness of the importance of considering resource peaks. Figures quoted above that state that we still have 60-130 years' supply of phosphate are meaningless because they ignore the fact that, for most resources (including phosphate), some deposits are easier to extract than others. Understandably, mankind has generally mined the easy deposits first. The deposits that remain may be deeper, or in thinner seems, or less rich in phosphate (meaning much more rock has to be removed to get the same amount of phosphate), or in politically difficult areas. With all such resources it is more meaningful to ask when production will peak and start to decline. At the point where peak phosphate is reached, we should expect supplies to decline and prices to rise rapidly.
One recent analysis suggested that we are probably already past peak phosphate. And at the time of writing (summer 2008) the price has risen 700% in the last 15 months.
Nutrient Recycling
The EcoSanRes paper quoted above continues:
It imperative that we begin recycling phosphorus and returning it to the soil to decrease the need for mined phosphorus as artificial fertilizer. Within a half century, the severity of this crisis will result in increasing food prices, food shortages and geopolitical rifts.
...Most of the phosphorus consumed by animals and humans is excreted. By safely recovering the nutrients found in human excreta through ecological sanitation, it is possible to reduce the depletion of phosphorus reserves. Recycling of phosphorus from sewage sludge is, however, very costly, and alternative systems are needed.