A new study estimates how long mined metals circulate before loss

Almost every aspect of modern society relies on materials of limited quantity on Earth. To live within the limits set by our planet, we need to figure out how to make the most of what we extract, and reuse everything we extract. A new study published this week examines how close we are to achieving the ideal for 61 different metals.

Along the way, its authors find out how long different metals remain in circulation before they are lost, and determine the stage at which these losses occur. Although the lack of recycling is a major obstacle to a circular economy, it is far from the only one. For many metals, including some critical ones, we discard the huge amounts present in the ores we mine for various elements.

Remember your metals

Tracking that many metals throughout their life cycle is a huge challenge, but the authors were able to draw on previous work by Japanese researchers who developed the software model. called MaTrace. The model is designed to track the flow of materials from production to loss, estimating losses at each stage of the material life cycle based on empirical data.

Losses are tracked at a number of moments in the life cycle of the material. As for metals, they include the production of raw materials from ores, the use of metal in the manufacture of products and its loss during use of the product. Finally, at the end of the life of any product, the metal is either recycled or disposed of as waste. MaTrace can also track material flow through the recycling process (with its inevitable losses) and back to additional products.

To say this specifically, we can refer to something simple, such as iron, which is extracted from ores that are then processed. Both steps involve some loss of iron and any other metals that are in the same ore. Iron is eventually incorporated into foods, a process that can again lead to losses as foreign material is cut off – part of the excess is also sent to the recycling process. There are also losses during use that can be as simple as the proportion of iron that rusts into the environment. Eventually, some of the iron-based products will be recycled and the rest will be released into the environment.

Some figures needed to track the fate of metals, such as the efficiency of converting ore to metal, are easy to find. Others, like the percentage of indium that gets into electronics, are necessarily rougher estimates, and researchers warn against considering any amount here as a final estimate.

For their analysis, the researchers start with a kilogram of material and send it through MaTrace for 1,000 years or until all the metal is lost – whichever comes first. The authors conducted an individual analysis for each of the 61 metals and grouped them into a number of groups: ferrous metals (iron and its relatives), nonferrous metals, special metals, and precious metals. This has allowed researchers to identify common trends for materials commonly used in specialized industries.

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