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The Life Cycle of Metals in the Economy and its Associated Environmental Impacts

Brought to you by Stéphanie Muller and Ambroise Lachat from BRGM

To publish this article online, it was necessary to extract copper from a mine. This copper was used to make the circuit board of your computer, and the cables of the power grid. Other metals, such as aluminium and cobalt, also had to be extracted. On a global scale, nearly 9.1 billion tonnes of metal ores are extracted from the ground each year to provide the metals needed for a wide range of applications including construction, transport, energy and digital infrastructures. Given the energy and digital transition processes already underway in OECD countries and the development of emerging countries, the annual growth rate – and therefore consumption – is unlikely to decrease any time soon. For example, the International Energy Agency measured the following increase in critical metals demand from 2017 to 2022: a threefold in lithium demand, a 70% rise for cobalt and a 40% rise for nickel. 

After their extraction from the natural stock, metals follow one or numerous cycles, involving a number of processing activities (e.g. comminution, refining or recycling at the end of life). The purpose of these activities is to transform the metals for use in production systems and consumer goods. Each stage in this cycle requires the consumption of energy or consumables and emits pollutants into the environment. Hence, the environmental impact of these processes is both local, with respect to the ecosystems around the production sites (mines, refineries, etc.), and global, with respect to greenhouse gas (GHG) emissions and thus global warming and ozone depletion. 

In the case of copper, an ore containing between 0.5 and 5% of copper is turned into a concentrate with a copper content of 30% during the extraction and concentration stages. This operation generates greenhouse gas emissions, particularly during the energy intensive comminution process. It also generates mining waste that may contain metal sulphides. Finally, storing this sulphidic waste on mining sites creates a risk of acidic drainage. This can pollute the surface and/or groundwater around the mine. 

Given that the richest deposits have already been exploited, the average grade of the deposits mined today tends to be lower. Consequently, this means more mining waste (tons of waste/tons of concentrate) and higher energy consumption (kWh/tons of concentrate) for the same amount of copper produced. Metal recycling could limit environmental impacts… 

Recycling is a common circular economy strategy. Its aim is straightforward: to transform the waste collected into secondary materials that can be reintroduced into the production processes at a later stage. Now, it is worth noting that recycling processes also have an impact on the environment, mainly through their energy consumption, but their treatment processes also have a direct impact on the ‘quality’ of the resource to be recovered. Specifically, this means that waste can be equally turned into a product of greater or lower quality and value than the original product. Making efficient use of resources thereby limits any loss in quality or value throughout their various cycles. 

Charpentier-Poncelet et al. calculated the average life span of 61 metals in the anthroposphere. Their model used a short-time perspective, and a metal is considered lost if it is dissipated into the environment in the form of emissions or if it is stored as waste. In order to determine the average life span of a metal in the anthroposphere, losses were compiled year by year..  

The average lifespan varies a lot depending on the type of metal. It varies from less than one year for gallium and selenium to 154 years for iron and almost 200 years for gold. In general, the average life span of metals in the anthroposphere is longer for ferrous, non-ferrous and precious metals, and shorter for so-called specialty metals. The study by Graedel et al. (2011) highlighted the very low recycling rates for these metals. Today, we observe that specialty metals have a wider range of dissipative uses, for example the use of tungsten for cutting tools. Losses also occur during the waste collection and treatment phase, where efficiency rates are lower than in primary production. For example, when alloys are remelted, the dust and slag may include metals such as zinc or chromium, which are therefore no longer accessible. 

As a result, the anthroposphere requires a continuous supply of primary metals, not only to meet ever-increasing market demand, but also to renew the portion of consumption that is irretrievably lost with each life cycle of the metal. 

With its functionalities, by enabling the selection of the most circular and sustainable strategies to put in place, the CE-RISE information system will foster application of circular economy strategies of product. It will help increase metals’ lifespan in the economy and postpone their final loss. This leads to the efficient use of resources while helping to limit the primary extraction of metals and its associated environmental impacts.