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Importance of phosphorus

<p>Most of you are probably familiar with the concept of “peak oil.” In the early days of oil, a relatively small amount was extracted. Soon, the appetite for oil grew.</p>

Most of you are probably familiar with the concept of “peak oil.” In the early days of oil, a relatively small amount was extracted. Soon, the appetite for oil grew.

Extraction increased exponentially, in proportion to the growth in industry, the exploration of the resource, advances in extraction technologies, and development of skilled personnel in the extraction industry. Later, oil extraction had to begin coming to terms with the finiteness of the resource. Each new barrel becomes marginally more difficult to extract, more energetically expensive. As a result, production peaks before the resource runs out.

This is not a story about oil, but about phosphorus. However, the example of peak oil gives us a model most of us can relate to regarding extraction of finite natural resources. Phosphorus is such a resource, and it appears we passed “peak phosphorus” about 20 years ago.

So what? Most of us rarely think about phosphorus. Heck, most of us probably don’t know much about phosphorus other than it’s being taken out of our dishwasher detergent. The significance is that phosphorus is a necessary element for plant growth (and for growth of all things). When we harvest crops, we are removing phosphorus that must be replaced to sustain agricultural production. This is particularly the case in areas of the world with older, weathered soil; in other words, areas with the largest populations and most rapidly expanding industrial agriculture.

Most of the phosphorus used in industrial agriculture is mined from rock and easily accessible sources are becoming rarer. As with oil, the marginal cost of mining phosphorus is increasing. This can be expected to affect food supplies and costs. Further, it contributes to social justice imbalances, as many of the poorest countries also have the poorest soils. As cheap sources of phosphate fertilizer disappear, these countries will become more dependent on richer countries (with richer soil) for food.

Current best estimates for when we will run out of phosphorus are 50 to 130 years. This is far enough in the future that our short-sightedness may cause us to ignore the problem for years to come. As we run low on oil, we can shift to other sources of energy. It presents challenges, but this is the direction we are moving. The problem is, there is no substitute for phosphorus. No other element can take its place in supporting life.

The good news is, unlike oil, phosphorus is a recyclable resource. We can reuse the same atoms of phosphorus again and again, as long as we don’t lose it down the drain, or down the stream, or down the landfill pit. We will need to be more careful with our use of fertilizers and with our management of organic wastes. Any phosphorus lost to runoff or buried is no longer available for supporting agriculture and, ultimately, us.


Andrew Laursen is an assistant professor at Ryerson University, studying ecosystem ecology. Sophia Dore is an environmental scientist with Conestoga-Rovers & Associates, an environmental consulting company.

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