Recycling rate vs recycled content

The average recycled content of steel today is around 31%1 . But steel’s recycling rate is estimated at 85%. What’s the difference? And which is the better measure?

Simply put, recycled content refers to the proportion of scrap in the steel something is made out of. If I am making steel cans, and half of the steel I use is scrap and half comes directly from iron ore, then I could claim that the steel in the cans has 50% recycled content. This is like saying that paper has 85% recycled content, or a plastic bag is made of 100% recycled material. As ever, there is devil in the detail – see ‘Recycled content – giving it 110%’ – but that’s the basic idea.

The recycling rate, in contrast, refers to the proportion of a material that is recovered and recycled. So if 90% of steel cans are recovered and recycled after they have been used, then the end-of-life recycling rate for steel cans would be 90%. See ‘Calculating the recycling rate: the devil in the detail’.

As illustrated in the intro, the values for recycled content and recycling rates can be very different. Firstly, because scrap can come from many things apart from steel cans. I could be throwing away all my steel cans in landfill, and making my new cans entirely out of scrap from old car parts. In that case the recycling rate for my cans would be 0%, even as their recycled content is 100%. Or it could be the other way around – all steel cans might be collected and recycled, but they are made into other products. In that case the steel can recycling rate would be 100%, but their recycled content would be 0%. There are plenty of examples of this in real life: the recycling rate for old cars is likely to be well over 90%, but because the steel used to make cars has very stringent quality specifications its recycled content is relatively low.

But there’s another reason for the difference between recycled content and recycling rates for steel, which may be more important. Steel production has been increasing over time. In 1990 the annual production of crude steel was about 770 million tonnes. By 2020 it was 1,882 million tonnes. If the average life of steel products is 30 years, then even if all of the steel produced in 1990 were recovered and recycled at the end of its use life in 2020 (a 100% recycling rate), the average recycled content of the steel made in 2020 would still be just 39%2. Most of the steel that was produced in 2020 will not become available for recycling until 2050 or beyond.

The time lag between steel production and end-of-life steel recovery and recycling means that the recycled content figure will lag behind the recycling rate, even if all steel is recovered and recycled. But it has another implication which depends on the rate of increase of steel demand. If steel demand increases exponentially, recycled content will stay the same. But if the increase in demand is less than exponential, then recycled content will increase even if the recycling rate remains the same. This will be the case for steel – the only questions are how soon and how fast.

So which measure, recycled content or recycling rate, is the better indicator of the steel sector’s success in recycling? Well, neither figure gives a full picture.

Recycled content tells us something about the extent to which steel demand is being met by the supply of scrap. That tells us something about how much primary iron production is needed to bridge the gap. It also tells us something important about the expectations we should have in terms of the greenhouse gas emissions associated with steel production, and whether those emissions are high or low both for the sector, and for specific products. At the global level we should expect the steel sector’s greenhouse gas intensity to come down over time due simply to the increased average recycled content – even with no improvement in scrap recovery, no improvement in the performance of electric arc furnace steelmaking, and no improvement in the performance of primary iron production.

And when comparing steel products, if a product has a high recycled content it should have a low carbon footprint when compared to a similar product made with a greater primary metallic input. Perhaps surprisingly, that does not mean it is necessarily the better choice if you want to reduce greenhouse gas emissions – something we will come back to in future posts. Whether it is a good choice depends not just on the recycled content, but also on the recycling rate.

The recycling rate tells us something about the potential to bridge the gap between scrap supply and steel demand by increasing the collection and recovery of steel at the end of a product’s life in use. If the end-of-life recycling rate is relatively low, then a valuable resource is going to waste. If we can collect and recover more scrap then that would have a major impact in reducing greenhouse gas emissions from steelmaking – so a low recycling rate tells us that we should devote resources to trying to increase it. But if the end-of-life recycling rate is already very high, then there is relatively little scope to increase it further. In that case we should focus our effort and investment elsewhere, if we want to fight climate change effectively.

Footnotes

  1. 3-yr average (2020 – 2022) of global crude steel production = 1910 Mt, from World Steel in Figures 2023. 3-yr average global scrap consumption for steelmaking (2020-2022) = 625Mt, data extrapolated from World Steel Recycling in Figures 2017 – 2021. Assumed global average yield loss for crude steel production = 5%. Recycled content = 625/(1910 x (100/95)) = 31.1% ↩︎
  2. Assuming a yield loss for crude steel production of 5%. Recycled content = 770/(1882 x (100/95)) = 38.9%. Not considering consumption at iron and steel foundries. ↩︎

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