Peak phosphorus: the crunch time for humanity?

by Dana Cordell, Stuart White and Tom Lindström The element phosphorus underpins our ability to produce food. Yet only recently has a vigorous debate emerged regarding the longevity of the world’s main source of phosphorus – phosphate rock.

Like oil, the world’s economy is totally dependent on phosphate rock. But our dependence on the latter differs: while oil can theoretically be replaced with solar, wind or biomass energy, there is no substitute for phosphorus in crop growth and hence food production. A scarcity of phosphate rock is therefore likely to threaten the world’s ability to produce food in the future if concerted efforts are not soon taken by policy makers, scientists, industry and the global community. While the critical point in time for phosphorus scarcity is highly uncertain and contested, all agree that demand for phosphorus is growing, and remaining phosphate rock is becoming increasingly scarce and expensive.

Global Phosphate Reserves

Surprisingly, the most recent estimates of longevity of phosphate rock reserves take a simplistic approach that divides the reserve (in million metric tonnes, Mt) by current consumption rates (approximately 160 to 170 Mt per year -- or 176 million to 187 million regular tons) to yield the lifetime of the reserves in years (1). The recent study by the International Fertilizer Development Center (IFDC) used this approach to yield an estimated 300 to 400 years lifetime for global reserves (see Figure 1, Scenario B). However, assuming that 100% of the reserve will be accessible and that consumption will not increase is inappropriate. Global phosphorus demand will increase to meet the food demand of the one billion people who are currently hungry plus the additional demand created by an expected two to three billion new mouths by 2050 (2). Additionally, phosphate demand will rise to satisfy increasing preferences for more meat and dairy products, to fertilize currently phosphorus-deficient soils (especially in Sub-Saharan Africa) and to grow biofuel crops and other non-food products that require phosphorus. Due to the non-homogeneity (or "patchiness") of phosphate rock and most other non-renewable resources, the easier to reach and high-grade reserves are typically mined first. There is consensus that the world’s remaining phosphate reserves are declining in phosphorus concentration, increasing in impurities and becoming harder to physically access. Meanwhile, phosphate extraction increasingly generates more pollution and waste, requires more energy per nutrient value and costs more to mine and to process.

While the element phosphorus is not scarce in the earth’s upper crust, the amount that can be accessed for productive use in food production is orders of magnitude smaller due to a wide range of bottlenecks including physical, economic, technical, geopolitical, legal, ecological and environmental constraints. From a food security and sustainability perspective, the most important quantity is not the total amount of phosphate rock in the ground but the fraction that is available to be accessed by farmers and applied to agricultural fields for food production. This fraction depends on a range of factors including the concentration of the phosphate deposit, levels of contamination, the cost of energy as well as the potential for new discoveries and technological advances. The exact fraction is therefore uncertain and will change over time depending on the influence of these factors.

Estimating Peak Phosphorus

The peak phosphorus curve provides a more realistic picture of this important estimate. That is, the peak phosphorus curve identifies the point in time when the production of high-quality and relatively inexpensive phosphate rock reaches a peak due to economic and energy constraints despite growing global demand (Figure 1). Predicting the exact year of peak phosphorus production is nearly impossible due to unpredictable factors (such as new agricultural policies, global financial booms and crises, geopolitical instability or market distortions), and, indeed, the peak is more likely to be a lumpy plateau as with peak oil. However, the peak phosphorus analysis tells us that the critical point in time for phosphorus scarcity will occur far sooner than when 100% of the resource is depleted. In 2007, Dery and Anderson arrived at a peak production year of 1988 (3). This analysis was inaccurate because they did not presume a total reserve value and only used historical production data until 2006. Fixing the area under the production curve to an assumed reserve value plus cumulative historical production is key to estimating a future peak. Otherwise, the estimated peak will be highly unreliable due to the variance of phosphate production data from year to year. In 2009, Cordell, Drangert and White published a peak phosphorus curve based on the latest USGS 2009 phosphate reserve data (4). This analysis resulted in a peak year around 2035. The study cautioned that while the exact timeline may vary, the fundamental problem of phosphorus scarcity would not change. More recently, the new IFDC study suggests: "there is no indication there is going to be a ‘peak phosphorus’ event within the next 20-25 years" because reserves have been re-estimated at 60,000 Mt, up from 16,000 Mt. However, no peak phosphorus analysis was actually undertaken to support such a claim.

If the 60,000 Mt IFDC reserve estimates are indeed correct, policy-makers, farmers, industry, scientists and the general community should be clear on what the IFDC report changes and what it does not change. While the timing of the peak would change, the threat of peak phosphorus this century remains. A revised peak phosphorus analysis by Lindstrom, Cordell and White (5) using Bayesian statistical methods takes into account both the Cordell et al. (2009) results and the IFDC reserve figures of 60,000 Mt. This analysis indicates a probable peak between 2051 and 2092 with a mean of 2070. At best, the new reserve estimate "buys time" until more substantial changes to our use of phosphorus become necessary.

Phosphorus and Sustainability

Despite the debate on the critical point in time when demand will exceed supply, what is clear is that our current phosphorus use patterns constitute an unsustainable situation of global proportions. First, access to phosphorus is already inequitable: many of the one billion currently hungry people are poor farmers working with phosphorus-deficient soils who cannot access fertilizer markets. Second, the unequal distribution of phosphate reserves means that a single country, Morocco, controls a major proportion of the world’s remaining high-quality phosphate reserves. Third, cheap fertilizers will become a thing of the past as cheap and high-quality reserves are depleted. Fourth, price spikes of phosphate commodities (like the 800% price spike in 2008) can be expected more frequently, making importers in places like India, Sub-Saharan Africa, Australia and the European Union more vulnerable. Fifth, an inefficient and "leaky" food production and consumption system means that only a fifth of the mined phosphorus reaches the food on our dinner plates. Finally, current human use of phosphorus for food production has led to a global epidemic of freshwater eutrophication and marine "dead zones," which threaten many of the world’s potable water supplies and endangers aquatic biodiversity.

These six chronic problems alone should be enough to warrant the attention of our political leaders and cause them to secure local and global phosphorus to feed the world. Achieving phosphorus security is by no means simple. However, it is possible: there are huge efficiency gains to be made not only in agriculture but also "upstream" in the mining and fertilizer sectors and "downstream" in food processing, retail and consumption. Further, unlike oil, phosphorus is not lost to the atmosphere once used. Hence, if we’re smart, we can recover used phosphorus from our excreta, food waste, manure and even fertilizer and mine waste.

References Cited:

(1) IFDC (2010), World Phosphate Reserves and Resources, International Fertilizer Development Center, Washington D.C.

(2) FAO, More people than ever are victims of hunger, 2009, Food and Agriculture Organization of the United Nations, Press Release, June 2009.

(3) Dery, P. & Anderson, B. (2007), Peak phosphorus. Energy Bulletin.

(4) Cordell, D., Drangert, J-O. and White, S. (2009), The story of phosphorus: Global food security and food for thought. Journal of Global Environmental Change, 19(2): p. 292-305

(5) Lindström, T., Cordell, D. & White, S. Improved peak phosphorus estimations: determining the real crunch time for food security, forthcoming article.

Other Supporting References:

Cordell, D. & White, S. (2011), Peak Phosphorus: clarifying the key issues of a vigorous debate about long-term phosphorus security. Sustainability, 1 (2011), ISSN 2071-1050. (in press).

GPRI (2010), GPRI Statement on Global Phosphorus Scarcity, Global Phosphorus Research Initiative, 26th September, 2010.

Gilbert, N. (2009), The Disappearing Nutrient. Nature, 461, 8 October 2009, pp.716-718.

Jasinski, S. M., "Phosphate Rock," Mineral Commodity Summaries 2011, US Geological Survey, January 2011.

Contributors' Biographies:

Dana Cordell is a Research Principal at the Institute for Sustainable Futures at the University of Technology Sydney where she undertakes and leads research projects on sustainable resource futures. She co-founded the Global Phosphorus Research Initiative (GPRI).

Stuart White is Director of the Institute for Sustainable Futures at the University of Technology Sydney where he leads a team of researchers who create change towards sustainable futures through independent, project-based research. He co-founded the Global Phosphorus Research Initiative (GPRI).

Tom Lindström is a theoretical ecologist, working as a postdoctoral researcher at the Department of Physics, Chemistry and Biology (IFM) at Linköping University in Sweden. Currently, he is currently a Visiting Fellow at the School of Mathematics and Statistics, Faculty of Science, at the University of New South Wales in Australia.