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Keywords:

  • phosphorus scarcity;
  • peak phosphorus;
  • synergies;
  • sustainable development challenges;
  • food security

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY
  5. SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES
  6. CONCLUSIONS
  7. REFERENCES

Global food production is dependent on constant inputs of phosphorus. In the current system this phosphorus is not predominantly derived from organic recycled waste, but to a large degree from phosphate-rock based mineral fertilisers. However, phosphate rock is a finite resource that cannot be manufactured. Our dependency therefore needs to be addressed from a sustainability perspective in order to ensure global food supplies for a growing global population. The situation is made more urgent by predictions that, for example, the consumption of resource intensive foods and the demand for biomass energy will increase. The scientific and societal debate has so far been focussed on the exact timing of peak phosphorus and on when the total depletion of the global reserves will occur. Even though the timing of these events is important, all dimensions of phosphorus scarcity need to be addressed in a manner which acknowledges linkages to other sustainable development challenges and which takes into consideration the synergies between different sustainability measures. Many sustainable phosphorus measures have positive impacts on other challenges; for example, shifting global diets to more plant-based foods would not only reduce global phosphorus consumption, but also reduce greenhouse gas emissions, reduce nitrogen fertiliser demand and reduce water consumption. Copyright © 2011 Society of Chemical Industry


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY
  5. SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES
  6. CONCLUSIONS
  7. REFERENCES

In order to boost agricultural productivity to the levels required to maintain our resource-intensive consumption patterns, while at the same time catering for an increasing global population, we require a constant input of phosphorus fertilisers. Some regions, including several European countries, might be able to cope for a significant period with only small external inputs due to long-term accumulated phosphorus in the soils. However, large regions with phosphorus deficient soils in sub-Saharan Africa require substantial nutrient enrichment to increase agricultural productivity. Phosphorus is a basic element, and essential for all growth. It cannot be substituted or manufactured and is a critical resource to ensure future food security. Historically, phosphorus has been supplied for crop production in manure, human excreta, bone meal and to some extent through guano,1 but since the discovery of phosphate rock in the 19th century, the rapidly increasing demand for mined phosphate rock has dominated global fertiliser production and has contributed to supplying food to billions of people.2 Today, around 90% of the world's mined phosphate rock is used for agricultural and food production, predominantly for fertilisers and to a lesser extent for animal feed and food additives.3 Phosphate rock is fossil sedimentary and igneous deposits with high content of phosphorus that have accumulated over tens to hundreds of millions of years, predominantly on the ocean floor, and are therefore a finite resource on a human timescale. Production of high-quality phosphate rock is predicted to reach its peak this century, possibly as early as the next few decades, despite growing demand for phosphorus fertilisers.4, 5 Phosphorus is the 11th most abundant element of the earth's crust. However, the amount of phosphorus in the earth's crust does not correspond to what is available and accessible to farmers and thus for global food production. Only a small percentage will be extractable due to physical, economic, energy or legal constraints.6 Further, phosphorus losses during mining of phosphate rock, processing of phosphate fertiliser and in the multiple steps involved in food production are substantial. Only about one-fifth of the phosphorus in phosphate rock reaches the food consumed by the global population.4 This phosphorus is, to a large extent, leaching to the aquatic environment or the sediments of lakes, rivers and oceans or being deposited in landfills. In recent decades the quality and concentration of easily accessible phosphate reserves have been decreasing. At the same time, total phosphate production is increasing and is currently predicted to continue increasing by 2–3% annually.7 During the 2008 food crisis, fertiliser prices soared and the commodity price of phosphate rock increased by 800% over a period of 18 months. This vulnerability of the global phosphate rock market makes the identification and adoption of sustainable pathways to future food security all the more imperative.

The critical challenge of global phosphorus scarcity is directly linked to global food security and other sustainability challenges, and therefore needs to be analysed in a broader and more integrated sustainability context.1 Attaining sustainable pathways to phosphorus security will require both a decrease in phosphorus demand and an increase in alternative phosphorus supply sources.8 It will also require the identification of beneficial synergies with other current and future challenges to support planning and decision making.9

PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY
  5. SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES
  6. CONCLUSIONS
  7. REFERENCES

Much of the scientific and industry discussion has been focused on estimates of the rates of depletion of phosphate rock reserves. The exact timing of a peak and of the total depletion of phosphate rock reserves are, however, dependent on several parameters and are therefore uncertain. These parameters are related to (1) demand and (2) supply of phosphate rock. The demand-related parameters include population increase, dietary consumption patterns, agricultural efficiency, production and processing practices and losses and wastage throughout the food chain. Also, advances in the utilisation of alternative phosphorus supplies such as manure, human excreta, organic waste, bone meal, sewage sludge and other recovered or recycled sources, strongly affect the demand for fossil phosphate rock reserves. The supply side is characterised by great ambiguity due to the large uncertainty and currently decreasing quality of phosphate rock reserves, by technical advances, the price of raw input materials (such as sulfur and oil), and due to the fact that the term ‘reserve’ in itself is dynamic.6, 10

Over the past few years, an intensive debate has occurred in the scientific community and amongst industry stakeholders concerning the current reserves and the exact timing of the peak phosphorus.2, 4, 10, 11 Central to this debate have been differing views on what to include in stocktakes of phosphate rock reserves and how to estimate the critical point in time when supply becomes constrained. One of the general challenges faced when estimating mineral reserves is the problem of how to define (and measure) a reserve. According to the U.S. Geological Survey, reserves are that part of a resource that can economically be ‘extracted or produced at the time of determination’.12 As technology improves or prices increase, more of the resource is judged to be part of the reserve. A reserve is as such a dynamic concept and with this background, the complexity of the debate about global phosphate rock reserves and the timing of the peak, becomes evident.

Estimates of how long the world's phosphate rock reserves will last have varied in recent decades.13 Most studies have been based on the U.S. Geological Survey's Mineral Commodity Summaries12 which are based on individual countries' own estimates and on scientific or industrial assessment reports. The 2010 International Fertilizer Development Center (IFDC) report World Phosphate Rock Reserves and Resources10 addressed the reserve debate by reviewing several compilations and reports from as far back as the early 1970s. Predominantly based on 1989 and 1998 findings,10, 14, 15 the IFDC report concludes that the total reserves of Morocco/Western Sahara should be put at 51 billion tons of phosphate rock instead of the previously estimated 5.7 billion tons. Most other country estimates remained unchanged compared to earlier USGS data. This provides a vivid example of how variations in the methods of assessment and characterisation of a reserve can lead to large variations in estimates of its size. It also emphasises the urgent need for data transparency and improved data assessment. Furthermore, it is important to consider several factors other than the mere quantity of reserves. The P2O5 concentration, the presence of impurities, degree of contamination with heavy metals or toxic substances, the physical or legal accessibility, the distribution and the energy input required for mining and processing of remaining reserves are all of significance for assessing future availability. However, many estimates of the depletion of phosphate rock reserves10 simply divide total reserves by current phosphate consumption rates. The assumption that demand will not grow, and that 100% of the reserve will be mineable is currently creating the large gap between the different assessments. Whilst difficult to determine an exact year, peak phosphorus modelling takes into account the declining quality, accessibility and increasing costs of remaining reserves and assumes increasing demand.6 Based on the data provided by the U.S. Geological Survey16 for the global assessment of phosphate rock reserves4 estimated peak phosphorus to occur by 2033. According to the most recent data assessment by the U.S. Geological Survey,17 which took into account the IFDC study,10 the total estimated reserves increased significantly; however, the available amount accessible for agriculture remains rather uncertain since questions of quality, accessibility and concentrations are not addressed. However, if these estimates were indeed accurate, this would not remove the threat of peak phosphorus this century, it would simply shift the timeline out from 2033 by several decades.5, 18

The geopolitical distribution of phosphate rock presents a significant challenge regarding the accessibility of the remaining reserves to importing countries. While the U.S. Geological Survey12 suggested that 85% of the world's remaining phosphate rock reserves were controlled by just five countries, the IFDC report10 dramatically increased the estimate of the megatonnes of phosphate rock controlled by Morocco (Fig. 1). According to the IFDC10 data and the U.S. Geological Survey,17 Morocco alone now controls around 77–85% of remaining reserves, and the top five producing countries (including Morocco) together now control over 90% of global phosphate reserves. A significant share of the phosphate reserves under the control of Morocco are located in Western Sahara, a territory Morocco occupies in defiance of UN resolutions.19

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Figure 1. Remaining phosphate rock reserves by country indicating the changes in estimations from the USGS 201012 (left), with 85% of the remaining phosphate rock reserves in Morocco/Western Sahara (5700 Mt), China (3700 Mt), South Africa (1500 Mt), Jordan (1500 Mt) and the USA (1100 Mt). Data for USGS 201117 (right) with 77% of the total share in Morocco/Western Sahara alone (50 000 Mt) and a minor total share for the six consecutive countries (China 3700 Mt; Algeria 2200 Mt, Syria 1800 Mt, South Africa 1500 Mt, Jordan 1500 Mt, USA 1400 Mt). Data visualisation from Uniview visualisation software by SCISS AB.

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The geopolitical implications of the inequitable distribution of phosphate resources have so far not been addressed sufficiently by the scientific community or by any international agency,1 with the exception of the European Commission, which recently commissioned a study into the implications of phosphorus scarcity for the European Union, a region almost totally dependent on imported phosphate for food and agricultural production.20 In light of these geopolitical challenges, the discovery of more reserves does not resolve the broader sustainability challenges of the dependence on phosphorus for global food security. On the contrary, this issue needs to be framed in a broader and more integrated way which more explicitly identifies the linkages between phosphate scarcity and other global sustainability challenges in a way which explores synergies that may promote the sustainable use of resources1, 21 (see Fig. 2).

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Figure 2. Identifying positive synergies between sustainable phosphorus measures and managing other global sustainability challenges.21.

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SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY
  5. SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES
  6. CONCLUSIONS
  7. REFERENCES

To determine pathways to sustainable phosphorus futures, demand management measures to decrease global phosphorus demand for food production, whilst ensuring food security, need to be taken into consideration. The potentially increasing need for phosphorus for the production of biomass for energy depending on the selected crop22 also needs to be taken into account. Future sustainable phosphorus scenarios, based on the concept of phosphorus security,1 focus both on decreasing the future demand for phosphorus and on alternative sources of supply to meet this demand. They also focus on achieving national phosphorus security to reduce a country's vulnerability to long-term phosphorus scarcity and short-term volatility in price and availability, thereby increasing the resilience and sovereignty of local and regional food systems.1, 23

Global sustainable development implies an integration of its three key dimensions: environmental protection, social development and economic development.24 Sustainable development as a ‘meta-goal’ for different regimes ‘offers considerable scope for synergies’.9 As such, the identification of synergies between responses to a range of sustainability challenges provides an important basis for future strategies. It opens up the possibility of increased efficiency and other benefits from the linking of sustainable phosphorus measures to other global sustainability challenges. Several studies have pointed towards the importance of linking climate change with sustainable development and the potential benefits from doing so.9, 25 A similar approach can be applied to phosphorus and sustainable development. Sustainable phosphorus measures are closely linked to several of the ‘planetary boundaries’,26 including climate change, global freshwater use, the eutrophication of surface waters and coastal zones, changes in land use, and chemical pollution. Further, these measures address several of the Millennium Development Goals and Targets,27 such as the eradication of poverty and hunger and the sub-targets on environmental sustainability which predominantly address the loss of environmental resources, access to safe drinking water and basic sanitation.

To identify sustainable future pathways, it is necessary not only to analyse linkages between the sustainability areas, but also to address the need for stakeholder engagement in the research process, to evaluate policies and their, sometimes unintended, effect.9

A number of positive synergies linking sustainable phosphorus use to other sustainability challenges, such as climate change, food security, freshwater use and sanitation, are relatively direct. One of the key positive synergies between sustainable phosphorus use and food production is changing from diets high in meat and dairy to more plant-based diets, which not only substantially reduces phosphorus demand8 but significantly decreases both greenhouse gas emissions and consumption of natural resources (such as water). This issue has been extensively discussed for freshwater use28 as well as for land and energy use, and is one of the crucial changes that could reduce the demand for phosphorus.8, 29 Another directly linked sustainable phosphorus use measure is to decrease phosphorus losses in: agriculture, food production, distribution and retailing and in the household, where up to 30% of the total purchased volume of food is discharged as waste.30, 31 Similarly, the contribution of food production to greenhouse gas emissions32, 33 would be decreased significantly by any of these measures and they would also increase the capacity to feed the growing global population. Likewise, integrating livestock and crop production is a measure that could facilitate the re-use of nutrients, decrease energy consumption, decrease greenhouse gas emissions, and decrease the impact of monocultures on biodiversity.34 Recovering phosphorus from human excreta for re-use as a fertiliser would not only contribute to local and regional phosphorus security, but also (1) facilitate sanitation provision for the 2.6 billion people currently without toilets; (2) protect local aquatic environments by preventing nutrients in wastewater systems reaching water bodies; and (3) contribute to community energy generation if biogas from anaerobic digestion of excreta is collected prior to the biosolids being re-used as fertiliser.35, 36 Improvements in efficiency at the mining stage would also support the technical advances that the mining and fertiliser sector expects over the next several decades,3 and respond to anticipated decreasing ore grades and increases in the costs of energy. A decrease in the dependency on fossil reserves from a small number of geographical regions would also address the need for regional resilience and would decrease the vulnerability to global, political and environmental changes. Securing a greater diversity of phosphorus sources for food production, ranging from an efficient re-use of manure and human excreta to a synergetic re-use of organic waste will also increase the capacity to adapt to changing conditions for local food production, as would potentially the use of algae for energy and fertiliser production.

CONCLUSIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY
  5. SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES
  6. CONCLUSIONS
  7. REFERENCES

Although global phosphorus scarcity is a crucial area for sustainability research, not much attention has been spent on this issue from a resource perspective. The ongoing debate over the exact size and longevity of remaining phosphate reserves has pre-occupied the scientific community over the past years. However, the important task that remains is to identify linkages and synergies with other global sustainability challenges to identify and implement pathways to a sustainable phosphorus future. Important research contributions are needed in several fields. Firstly, an analysis of the economic dynamics of phosphorus, including life-cycle energy costs, both for phosphate rock-based food systems and for renewable phosphorus supply options. Secondly, an analysis of the risk and consequences of future price spikes. A third area requiring study is the implications and possible response to the inequitable distribution of, and access to, phosphate fertilisers, including the sub-Saharan African case where farm-gate prices are significantly higher than in the United States or the European Union.

Scientific research for a sustainable phosphorus future also requires an increased focus on the virtual flows of phosphorus, i.e. the embodied phosphorus required to produce traded commodities, to determine the real national and regional dependency on phosphorus. This research needs to investigate both direct fertiliser flows, and flows via food commodities. It is particularly important to detect specific regional vulnerabilities to phosphorus scarcity and to assess the capacity to adapt to changing preconditions in food production. To identify both negative and positive synergies for sustainable phosphorus use measures, decision-makers industry and scientific experts need to be involved in a participatory process for analysis and decision support. New and transparent scenarios on future demand and supply of phosphorus for alternative futures are thus required to support decision makers and planners to evaluate options for future food and energy production.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PEAK PHOSPHORUS AND GLOBAL PHOSPHORUS SCARCITY
  5. SYNERGIES FOR SUSTAINABLE PHOSPHORUS FUTURES
  6. CONCLUSIONS
  7. REFERENCES
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