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Ambitions for renewable energy are high. Countries in the developing world have cottoned on to building renewable micropower plants to cut costly fossil-fuel imports and increase rural electricity access. Industrialized countries hope to slash emissions. Prices of solar photovoltaic cells are falling, inspiring great optimism. Out of the world's 193 countries, 144 had set targets for renewable energy deployment by early 2014, up from 138 the previous year¹. They range from the tiny Caribbean island of Grenada targeting 20% renewable energy by 2020, to Germany's aim for 60% by 2050.

But this promise ignores a flip side. Mineral requirements for new renewables are likely to contribute to fresh environmental damage, while mining constraints could obstruct planned emissions cuts. That dilemma emerged in 2009 when China suddenly shut down its exports of rare earth metals, which are used in wind turbines. Substitutes were found, so the scare has passed but geologists at CNRS, France's science research centre, have drawn attention to an inconvenient problem relating to a whole range of metals.

“A shift to renewable energy will replace one non-renewable resource (fossil-fuels) with another (metals and minerals),” claims Olivier Vidal, an Earth scientist at the CNRS, in a recent paper². Vidal notes the massive increase in metals and minerals needed for the world to fulfil aspirations to cut greenhouse-gas emissions. He estimates that 3,200 million tonnes of steel, 310 million tonnes of aluminium and 40 million tonnes of copper would be needed to build the latest generations of wind and solar facilities. Based on a 2050 100% renewables scenario by NGO WWF³, these projections exclude metals demand from electric vehicles and other transport. The steel requirements compare with 1,649 million tonnes of crude steel produced in 2013⁴. Vidal's investigation indicates that the metals required correspond to a 5–18% annual increase in global production for the next 40 years.

The European Union 2050 energy roadmap⁵ notes that an EU 80–95% greenhouse-gas emissions cut by 2050 means sourcing two thirds of energy from renewables, altering the above estimates. To this rise in production would be added the accelerating global demand for ferrous, base and minor metals from developing and developed countries.

“The increase in aluminium, copper and iron production needed for the construction of solar and wind facilities to 2050 will be similar to that driven by all industrial sectors between 1970 and 2000,” says Vidal. One of the problems is a metals lock-in lasting 20–30 years as new wind farms and solar plants now being built cannot be quickly recycled. For instance, just 1% of all photovoltaic modules have reached the end of their 30-year lifetime. Yet the coming period coincides with a major leap in renewable energy construction, much of which will depend on virgin materials.

Given these startling numbers, it is easier to visualize renewables' demand for less common metals. Solar photovoltaic cells, which use silver for a conductive paste, will consume 109 million ounces of the precious metal in 2018⁶ in a market predicted to grow by 27% by then. This is 16% of total industrial demand for silver, forecast at 680 million ounces in 2018, the largest for any individual industrial sector. Industrial demand constitutes about half of the silver market. Solar photovoltaic cells compete for silver with the automotive and battery sectors, among others. Meanwhile, about 60% of copper available is used to conduct energy through any type of energy system, because it is the best metal conductor for electricity and heat.

Making sense of this, of course, demands knowledge of supply sources and volumes. Only the crisis in availability of rare earth metals shocked manufacturers into realizing their level of dependency on monopolized metal sources. For instance, China is the world's largest source of rare earths (97%) alongside 83% of gallium and 58% of silicon — all used in renewable energy. Chile is responsible for 44% of lithium, used in batteries, and 31% of copper production⁷.

Greater awareness of these limiting factors explains doubts about producer ability to fulfil targets by sourcing raw materials when they need them. Copper is an especially critical case, and considered relatively scarce with only 60 years of availability remaining at current production levels⁸. Copper in existing installations may take decades to be recycled and is likely to use increasingly intense amounts of energy.

Mathijs Harmsen, formerly of Utrecht University's Copernicus Institute of Sustainable Development, foresees greater resource pressures on the metal in future: “the gross energy requirement of copper in a 2050 100% renewable energy system will be a factor 2–7 times larger than it is today...Because of an increasing in-use stock of copper, recycling will play a relatively small role even when the recycling rate is high,” he states.

ANTOFAGASTA PLC

Chilean copper mine.

1. Renewables 2014: Global Status Report (REN21; 2014).
2. Vidal, O., Goffe, B. & Arndt, N. Nature Geosci. 6, 894–896 (2013).
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3. The Energy Report: 100% Renewable Energy by 2050 (WWF/Ecofys/OMA; 2011).
4. Annual Crude Steel Production Per Country and Region 1980–2013 (World Steel Association; 2014). http://go.nature.com/iLIfFj
5. Energy Roadmap 2050 (European Commission, 2012); http://go.nature.com/xFtSs1
6. Glistening Particles of Industrial Silver (Silver Institute, 2014).
7. Herrington, R. Nature Geosci. 6, 892–894 (2013).
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8. Harmsen, J. H. L., Roes, A. L. & Patel, M. K. Energy 50, 62–73 (2013).
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9. 10-Year Network Development Plan 2014 (European Network of Transmission System Operators for Electricity, 2014).
10. Hartwich, E. G. et al. Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1312753111 (2014)
11. Critical Raw Materials for the EU: Report of the Ad-hoc Working Group on Defining Critical Raw Materials (European Comission, 2010); http://go.nature.com/jxy6yo

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Affiliations

1. Elisabeth Jeffries is a self-employed journalist based in London, UK