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Resource Demand Scenarios for the Major Metals Ayman Elshkaki, Thomas E. Graedel, Luca Ciacci, and Barbara K. Reck Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b05154 • Publication Date (Web): 30 Jan 2018 Downloaded from http://pubs.acs.org on February 7, 2018

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Environmental Science & Technology

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Resource Demand Scenarios for the Major Metals

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Ayman Elshkaki1, T. E. Graedel1*, Luca Ciacci1,2, Barbara K. Reck1

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New Haven, CT 06511, USA

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Center for Industrial Ecology, School of Forestry and Environmental Studies, Yale University,

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Department of Industrial Chemistry “Toso Montanari”, Alma Mater Studiorum - University of Bologna, Bologna 40136, Italy

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* Corresponding author. Tel.: +1-203-432 9733; Fax: +1-203-432 5556

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E-mail address: [email protected]

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ORCID ID: 0000-0002-4007-3189

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Keywords: Scenario, aluminum, copper, iron, lead, manganese, nickel, zinc

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1 ACS Paragon Plus Environment


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Abstract

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The growth in metal use in the past few decades raises concern that supplies may be insufficient

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to meet demands in the future. From the perspective of historical and current use data for seven

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major metals – iron, manganese, aluminum, copper, nickel, zinc, and lead – we have generated

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several scenarios of potential metal demand from 2010-2050 under alternative patterns of global

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development. We have also compared those demands with various assessments of potential

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supply to mid-century. Five conclusions emerge: (1) The calculated demand for each of the

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seven metals doubles or triples relative to 2010 levels by mid-century; (2) The largest demand

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increases relate to a scenario in which increasingly equitable values and institutions prevail

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throughout the world; (3) The metal recycling flows in the scenarios meet only a modest fraction

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of future metals demand for the next few decades; (4) In the case of copper, zinc, and perhaps

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lead, supply may be unlikely to meet demand by about mid-century under the current use

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patterns of the respective metals; (5) Increased rates of demand for metals imply substantial new

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energy provisioning, leading to increases in overall global energy demand of 21-37%. These

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results imply that extensive technological transformations and governmental initiatives could be

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needed over the next several decades in order that regional and global development and

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associated metal demand are not to be constrained by limited metal supply.

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TOC Art

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Introduction

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Modern society is completely dependent on the use of metals, especially the “major metals”, to

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enable transportation, housing, communication, and an almost infinite array of products and

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services. Despite the fact that metals and the benefits of their properties are deeply embedded in

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contemporary technology, detailed scenarios of metals based on historical supply and demand

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and responsive to alternative patterns of regional and global development have not emerged. The

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reason is relatively easy to understand by comparison with other resources. Energy, for example,

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is fungible – it can be supplied by fossil fuels, by solar power, or by other means, and studies of

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solar radiation and extractable oil and natural gas have a rich (if somewhat checkered) history. In

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the case of water, one need only consider a single molecule, although one that has its own cycle.

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Climate is quite challenging to address, but now has a history of several decades of effort by

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meteorologists and Earth scientists. Metals availability and use, in contrast, is at least equally

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complex, but is thus far relatively unexplored from a scenario perspective. It is easy to point to

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some reasons for this. First, the inherent complexity of the topic is indicated by the routine

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employment of more than sixty metals in modern technology1. Second, the potential for

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substitution of one metal by another without degradation of function is quite limited2. Third, the

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global resources of metals are not well quantified3-5. Nonetheless, the consideration of possible

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futures of metals is every bit as important as those of energy, water, or climate.

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To date, very few scenarios relate to future metal supply, demand, and environmental

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implications, and those that do so have not been based on individual metals, current and

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anticipated metal use in different principal applications, nor geological data limitations. Van

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Vuuren et al. (1999) addressed two metal groups: “AbAlloy” (Fe, Al, Cr, Ti) and “MedAlloy” 4 ACS Paragon Plus Environment

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(Cu, Pb, Zn, Sn, Ni), with climate implications rather than individual metal supply and demand

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as the central issue. That focus was also taken by the International Energy Agency (2011), which

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based its scenarios on historic data on greenhouse gas emissions from metal production, making

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no distinctions between metals and their various use histories and prospects. Allwood et al.

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(2010) assigned specific 2050 demands for iron and aluminum and explored various backcasting

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approaches to minimizing greenhouse gas production. In none of these efforts was a variety of

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metals addressed, nor were their individual industrial sector behaviors explored.

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In the present work, we draw on materials science, industrial sector analysis, and economic

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geology information to explicitly address plausible futures for metal supply and demand.

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Although almost all metals have unique uses, the “major metals”, which we define as iron (Fe),

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aluminum (Al), manganese (Mn), copper (Cu), zinc (Zn), lead (Pb), and nickel (Ni), are those

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that are employed most widely and in the largest quantities: the annual production of these

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metals constitutes more than 98% by mass of all the industrial metals combined6. The balance

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between supply and demand of these metals, now and in the future, is thus of both significant

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interest and substantial importance. In general, each of these metals has a small number of

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principal uses in which the bulk of its production is employed. These use histories are well

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known for the past few decades, providing information that can serve as a starting point for

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considerations of future demand.

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To explore possibilities in the next few decades from the perspective of the past, we have

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developed a set of scenarios directed toward metal demand to mid-century. Scenarios, which

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originated in military and business circles in the 1970s and 1980s e.g., 7, 8, have been used in



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recent years to explore the possible futures of resource supply, resource demand, and

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environmental implications. Examples include energy9, water10, and climate11. The purpose of

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such scenarios is not to predict the future, which they cannot do, but to stimulate thought and

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enable decision-makers to plan possible actions related to eventualities that might occur. Our

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scenarios, which we term the Yale Major Metal (YMM) scenarios, are built upon the foundations

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and perspectives of those for climate and energy9, 12, 13, and can be described briefly as follows

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(and in more detail in the Supporting Information): The Market World scenario essentially posits

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that those in the developing world (whose per capita income is expected to increase) will wish to

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acquire possessions similar to those typical of people in the more developed world , and that

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market forces will enable that to happen. The Toward Resilience scenario is similar except that

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government policies more respectful of renewable energy and the environment will be in force.

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The Security Foremost scenario tilts toward confrontation and isolationism rather than

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cooperation, with a consequent reduction in international commerce. Finally, the Equitability

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World scenario aims toward a more collaborative and inclusive world in which at least minimal

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material needs are provided to all. Whatever world awaits us, whether one of these or some

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other, it will need to be realized by the extensive use of the metals that we address in these

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studies.

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Materials and Methods

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It is useful in developing scenarios for the future magnitude of any variable to refer to the

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situation in the recent past. This approach is likely to be reasonably accurate for the major

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metals, at least for the foreseeable future, because most variables related to global processes and


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global material flows change slowly and because effective substitution requires large quantities

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of a suitable substitute. For the seven metals in this study we first identify their principal uses

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and the historical fractions of those uses. The total historic demand for the metals is then

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disaggregated based on use in different final product sectors, including buildings and

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infrastructure, transportation, industrial machinery, appliances, electronics, metal goods, and

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chemicals (Figure S2 in the Supporting Information). The analysis for the metals is carried out

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from 1980 to 2010 on a global level, with the exception of manganese, for which available data

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were for 1980 to 2008.

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The starting point for deriving future metal demand in the four scenarios is the global production

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of the seven metals in 2010. Metal demand then evolves on the basis of adopted annual

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percentages of growth. Growth rates are strongly connected to GDP/capita, given the evidence

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for high correlations between growth and individual wealth14-15. Projections for population and

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per capita income were based on research by Electris et al.13, the World Bank16, and the United

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Nations Population Division17-18. Where we have deemed appropriate, adjustments were made to

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growth rates in order to reflect anticipated increases in level of urbanization and the associated

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metal demands for housing and infrastructure19,20, substitution of materials2, and technological

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development

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that were utilized. The resulting percentages of growth that were employed for the seven metals

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over the time periods of 2010-2015 and 2025-2050 are given in Table S10. The energy supply

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and energy mix for the scenarios are derived from the International Energy Agency23 and are

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described in Section 3 of the Supporting Information.

cf. 21,22

. Table S3 in the Supporting Information provides the derived coefficients



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In an actual situation in the future, metal prices and thus metal demands would be expected to

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respond to price fluctuations. Because price has never been determined to reflect geological

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scarcity, however24, there appears to be no obvious approach to incorporating market dynamics

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in scenarios aimed several decades into the future. Our judgement is that the general thrust of our

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policy-related metal demand results would hold over time even in a market dynamics model,

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given the large flows into use of these metals and the general lack of suitable alternative

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materials for the principal metal uses in the next few decades. We choose, therefore, not to

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arbitrarily inject economic disruptions into our scenarios.

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Results and Discussion

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We have used the approach outlined above to study metal demand and supply for the seven

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metals, from 2010 to mid-century, under the drivers and constraints incorporated into the four

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scenarios. As an example of the results, Figure 1(upper left) shows the derived demand for iron.

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The four scenarios all show substantial increases in iron demand over time compared with the

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2010 value of about 1400 Tg Fe (million metric tons of Fe). The lowest final demand, for the

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Security Foremost scenario, is about 3250 Tg Fe in 2050. The Market World and Toward

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Resilience results are similar to each other at about 4200 Tg Fe in 2050. The Equitability World

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scenario generates the highest iron demand at about 5150 Tg Fe, or more than triple the demand

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of four decades earlier.

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Our metal demand results are consistent with those of other researchers, who have generally

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applied one-metal and often one-scenario approaches. Nonetheless, iron demand by mid-century

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in those studies is anticipated to double or triple5,25-26, aluminum demand to increase by three to

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eight times5,27-28, and demand for other widely used metals by two to three times5. These findings 8 ACS Paragon Plus Environment

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indicate that the metal demand results presented in this paper would not be deemed unrealistic by

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other researchers.

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Because iron is by far the most widely used metal, we would not necessarily expect that scenario

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features for the other metals would resemble those for iron. As it turns out, however, the iron

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results are qualitatively duplicated for the other six metals, as shown in Figure 1(right), and in

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additional detail elsewhere for copper29 and nickel30. This occurs despite the fact that we treat

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each metal individually by addressing its principal uses and the evolution of those uses over

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time. In all cases the calculated total individual metal demand by 2050 is some two to four times

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that of 2010, and for the metals the order of the metal demand growth in the scenarios, high to

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low, is the same. This is largely a consequence of the scenario factors that drive the demand for

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the metals, especially the increasing global population and the anticipated rise in global per

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capita wealth.

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Features of the results for the different development scenarios are also worth comment. As

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mentioned above, they are intended to explore quite different pictures of possible global

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development and thus of resource requirements. The four scenarios do indeed give quite different

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results, and it is of particular interest that the largest demands for metals emerge not from the

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Market World vision but from that of the Equitability World (Figure 1(right)). This is largely due

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to the growing urban populations in the developing country regions and to their increasing per

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capita incomes in the Equitability World scenario. Thus, from a resource perspective a more

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equitable future for the planet’s population implies a large increase in demand for the major

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metals.



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It is important to ask whether the metal demands of Figure 1(right) could be met by recycling. To

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respond to this question, in Figure 1(c) we compare the calculated demand for zinc as determined

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by historical demands, the life times of the major uses of the metals e.g., 31-32, the dissipative use

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of metals33, and recycling rates and efficiencies34 with the anticipated secondary (recycled)

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supply computed in the present work (Figure S11 in the SI). It is apparent that in a growing

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global economy that encompasses relatively high dissipation rates and long product life times,

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the supply likely to be available from recycling will be only a modest fraction (~15%) of that

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needed to meet demand. Zinc is merely a representative metal here; the derived secondary

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supplies of the other metals follow similar patterns with the exception of lead, in which a high

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fraction of its demand is met by secondary sources due to the relatively high recycling rate, low

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dissipative use, and short life time of its major end use application (batteries).

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If demand is unlikely to be met by recycling, what are the prospects for increased supply from

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primary resources? This issue can be addressed through the use of two geological measures: the

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“Reserves” (R, amounts in deposits that are currently economic to mine, a quantity that can be

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estimated reasonably accurately) and the “Resources to Mid-Century” (RMC, the roughly

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estimated global resource production potential to 2050). (Our sources for numerical values of

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these metrics are discussed in the Supporting Information.) Figure 2 illustrates the cumulative

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demand (2010-2050) calculated for each of the seven metals over the four developmental

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scenarios, expressed as wedges of the ranges of demand, highest to lowest. The gray region is

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centered on 100% of the approximate RMC for the metals. For four of the metals, nickel, iron,

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aluminum, and manganese, none of the scenario results exceed the estimated Resources to Mid-


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Century values by 2050, suggesting that there are no immediate supply concerns provided that

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there is adequate capacity to mine and process the currently identified ore bodies. This is not the

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case, however, with zinc, which can be seen to exceed the Resources to Mid-Century value in

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about 2034-2037, depending on the scenario, and for copper, which is calculated to exceed

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Resources to Mid-Century in about 2044-2048. A similar result occurs for lead, with Resources

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to Mid-Century exceeded in about 2041. However, the lead scenario is based to a significant

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degree on historic uses of lead batteries in motor vehicles. To the degree that electric vehicles

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displace internal combustion vehicles in the global market, the demand for lead that we derive

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may be overestimated.

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In fact, the anticipated supply situation may be even more problematic than suggested by Figure

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2, at least in the case of copper. Northey and colleagues35 have conducted a survey of global

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copper resources, historic mine production, and anticipated mine production, based on a

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combination of published data, information in corporate and public reports, and news releases.

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They use that information to predict copper production to 2100, and find a peak around 2030-

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2040 that declines just as demand from our scenario results increases (Figure 3). Copper

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recycling results from the scenarios can be seen from Figure 3 to ameliorate the challenge to

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primary copper supply to some degree, but not to significantly mitigate primary copper demand.

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Taken together, Figures 2 and 3 imply potentially significant limitations on copper supply in two

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or three decades.

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Similar studies for anticipated geological production have not yet been carried out for zinc, lead,

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nickel, aluminum, or manganese, but Mohr and colleagues36 have done so for iron. They find an

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iron production peak around mid-century, at about 75% more than 2010 production (inadequate

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to support the demand results illustrated in Figure 1(right)). Thus, the degree to which supply of

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metals can meet demand over the next few decades will depend not only on the amount of global

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resources but also on the degree to which available production capacity is available to expand

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appropriately.

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Increased rates of demand for metals imply substantial new energy provisioning, leading to

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increases in overall global energy demand of 21-37%, as shown in Figure 4. In line with metal

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demand, Equitability World has the highest energy use, and Security Foremost (with lowest

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metal demand) the lowest. (A detailed breakdown by metal in provided in Section 13 of the

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Supporting Information.) In a world in which concern about climate change is high, these

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potential increases in energy demand deserve careful consideration. Increased metal production

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will also require large amounts of water, but the relevant water requirements data are poorly

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quantified and thus water needs as a consequence of metal production are not part of the present

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scenario study.

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Given the enhanced metal demand results of the scenarios, we consider four actions that might

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be invoked in efforts to balance demand and supply: (1) achieving per capita saturation of metal

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demand; (2) substituting abundant materials for scarce metals, (3) enhancing recycling, and (4)

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maximizing primary production yields. Per capita saturation might be imagined to occur once


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one’s needs and desires as reflected in metal use have been satisfied. While not unreasonable as a

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concept, it turns out that, for the seven metals which our scenarios address, only for iron in

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France, the United Kingdom, and the United States have well-characterized examples of in-use

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stock saturation been shown to occur37. A study of less well-characterized stock buildup38

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suggests that an eventual iron saturation range for world regions is about 12.8-15.4 Mg Fe/capita.

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Merely this lower bound would imply an eventual global in-use stock of at least 120 Pg Fe (12.8

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Mg Fe/capita * 9.3 billion people), assuming that no major technological transformation occurs.

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Such a level would be well above the cumulative production predictions of Mohr and

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colleagues36.

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Although substitution for a metal in short supply would not seem at first glance to be an

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unrealistic goal, it nonetheless appears that no suitable substitutes are available for most of the

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seven metals’s major uses2. In cases where possible substitutes can be identified, the next

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consideration is whether the substitutes could be available in the quantities that would be

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required. We investigate this issue in Section 15 of the Supporting Information, where we show

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that the primary uses of all seven major metals relate strongly to buildings and infrastructure.

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These are sectors of use that appear quite difficult to quickly replace by alternative materials,

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especially at the magnitudes that would be required and particularly in the next two or three

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decades (see Table S12 in the Supporting Information). Overall, therefore, while material

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substitutions here and there wil be helpful, no substitutes appear sufficiently abundant to replace

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the total demand of any of the major metals even if their physical and chemical properties were

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found to be satisfactory.

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Could enhanced recycling rates meet the demand challenge? Some of the demands posited by the

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scenario results could surely be satisfied by recycling metal that is leaving use. However,

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although recycling rates can surely be improved, it seems unlikely that recycling could be

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sufficient to largely or completely satisfy demand, at least for many decades to come.

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So far as the topic of primary production yields is concerned, process inefficiencies are known to

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occur throughout elemental cycles, especially at early life cycle stages. Ore grades and the

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technologies used for metal extraction influence mining efficiency, and additional losses occur

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during subsequent processing (e.g., slags). For the seven metals, losses in primary production are

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listed in Table S6. The residues from mining activities (commonly known as “tailings”) may

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contain varying amounts of metals whose extraction is not economically feasible because of low

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concentrations. However, the depletion of primary deposits and the decline of ore grades39 are

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stimulating efforts towards optimal material extraction40. In particular, tailings could become a

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valuable source of primary material, and novel extraction practices (such as phytoextraction 41-43

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could help to exploit the potential for material recovery.

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As has been pointed out e.g., 44, the metal supply from Reserves largely reflects current demand,

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while potential supply from Resources to Mid-Century may be underestimated because

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Resources to Mid-Century is quite difficult to determine5. It is important to note, however, that

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key factors in metal primary supply include not only the magnitude and quality of the resource

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but also the rate and efficiency with which the target minerals can be extracted and processed. It

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is the combination of estimated quantity in ore deposits and potential rates of production that has

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been evaluated by Northey and colleagues35 for copper and by Mohr and colleagues36 for iron,


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and on which their estimates of peak extraction by mid-century are based. Because we cannot

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know with any certainty what future metal demands will be44, a high level of precision should

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not be implied for the results reported in this paper.

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It is also appropriate to reconize that supplies of these (and other) metals are potentially

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constrained by factors other than geological abundance and inadequate recycling. The energy

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and water requirements for mining and processing of ores, especially lower grade ores, are large

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and increasing5,45 . Other challenges include achieving and maintaining a social licence to

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operate mines in populated regions5,46, something becoming increasingly contentious in a world

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of social media interactions, as well as geopolitical instability in some mineral-rich countries47.

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Possible policy responses to evolving mineral supply and demand issues are discussed

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elsewhere44,47.

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In summary, we have conducted what we believe to be the first well-characterized scenario

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studies for the demand and supply of seven major metals, from the present day to mid-century. It

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is not appropriate to ask if the scenarios are "correct". Rather, the fundamental requirement for

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scenarios is that they describe plausible ways in which global societal/material evolution might

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occur. As such, the results of these scenarios provide the basis for considering the potential

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consequences should the results turn out to approximate actual situations seen to occur over time.

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Our results suggest that significant supply challenges for the major metals may lie ahead. If

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adequate supplies of these metals cannot be made available over time and at affordable prices, it

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may be quite difficult to extend to emerging economies the core technologies upon which the



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more developed world has depended for housing, transportation, energy provisioning, and other

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modern needs. The result could be a quite significant constraint to global development.

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Supporting Information.

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The Supporting Information is available free of charge on the ACS Publications website at

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1. The Yale Major Metal (YMM) scenarios and their storylines

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2. Historical metals use in different industrial sectors

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3. Analysis of the historical demand for metals

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4. Fitting the historical rate of use results to metals industrial applications

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5. Geological resource metrics

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6. Ore grade specifications

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7. Losses in primary production

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8. Dissipative losses of the metals

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9. Recycling rate/recycled content values

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10. Required metal production increases required to meet demand in the four scenarios

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11. Relative metal demand results in the four scenarios

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12. Metal demand by use results in the four scenarios

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13. Energy required to meet metal demand

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14. Primary metal supply compared to the Reserves and Resources to Mid-Century

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15. The potential for substitution

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ACKNOWLEDGEMENTS

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We thank the Nickel Institute, BP International, General Electric Global Research Center, Shell

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Global Solutions, the United Nations Environment Programme, and the U.S. National Science

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Foundation (Grant CBET-1336121) for useful comments and for financial support, T. Fishman

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for helpful comments on data analysis, and S. Mohr, G.M. Mudd, and S. Northey for sharing

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data from their work.

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Figure 1. Global metal demand for the four alternative development scenarios. Upper left: Iron

480

demand, 1980-2010 (historic), 2010-2050 (scenarios). Right: Relative demand for the seven

481

major metals in the four scenarios as indicated by the color ramp below the figure, in which “1”

482

indicates the 2010 demand. Lower left: Comparing demands (P) for zinc under the four scenarios

483

with the anticipated secondary supplies (S) (i.e., from recycling) derived from the scenarios.

484

Scenario abbreviations are: MW = Market World, TR = Toward Resilience, SF = Security

485

Foremost, EW = Equitability World.

486



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Figure 2. Cumulative global primary demand for the seven metals from 2010-2050, compared to Resources to Mid-Century (RMC), the very roughly estimated potential global resources production to 2050. The calculated demand for all four scenarios for a given metal are contained within its colored wedge. The gray region indicates the uncertainty of the RMC estimates for the metals.

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Page 25 of 26


80 80,000 EW

teragrams copper per year

70 70,000 TR MW

60 60,000

Total Demand

EW

50 50,000

SF TR MW

40 40,000

Total Supply

SF EW

30 30,000

TR MW

20 20,000

Primary Supply

Secondary Supply

SF

10 10,000 00 1960

495

1970

1980

1990

2000

2010

2020

2030

2040

2050

2060

2070

P

MW (S)

TR (S)

SF (S)

EW (S)

MW (T)

SF (T)

EW (T)

MW (TS)

TR (TS)

SF (TS)

EW (TS)

2080

2090

2100

TR (T)

496 497 498 499 500 501 502 503 504

Figure 3. Year-by-year total copper demand from the four alternative development scenarios (red curves) (T), compared with the primary copper production supply predictions of Northey et al.35 (solid black line) (P) plus the anticipated secondary copper supply derived from the scenarios (light blue curves) (S). The total copper supplies (TS, dark blue lines) are the sums of the Northey et al. primary production values (P) and the secondary production values calculated in this work (S).

505



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507 508 509

Figure 4. Cumulative energy demand for metals [EJ/yr] in the four scenarios.

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Resource Demand Scenarios for the Major Metals - Environmental

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