Increasing the circularity of steel for the automotive industry

In my last blog I referred to the need for a portfolio of innovations to support decarbonisation of steel for the automotive value chain. In this blog I want to look in more detail at the circularity of automotive steels, and what is needed for the future.

Steel circularity

Steel is a permanent material – it is used but never consumed, and its extraction is a long term investment for future generations. Steel is already a circular material – a closed material loop has existed for >150 years and steel is the most recycled material in the world because it is readily separately magnetically from other waste and has a commercial value.

Across all sectors, steel is in service on average for 38 years - steel entering service now may not be available for recycling until nearly 2060. And it is scrap from the 1980's that we are consuming today, when global steel production was only 30% of what it is today.

So while globally a large reservoir of future steel is being laid down for future generations, in the meantime, there is insufficient scrap to meet the worlds demand for steel – steel which will help the building of infra-structure for a decarbonised world. 

In fact global demand for steel is expected to continue until well beyond 2050, and because of the lag in scrap availability, demand for steel will exceed what can be made from available scrap until at least this time. So we need to decarbonise primary steel-making, urgently.

The circularity of automotive steel

Looking in more detail from an automotive perspective, WorldAutoSteel have shown that >95% of steel from end of life vehicles is recycled. So the material loop is almost completely closed already. There is no issue in ensuring that steel will be recycled - ferrous scrap has long had a value that makes it worth recovering and recycling.

High quality automotive steel scrap is of course available today, as pre-consumer scrap and from end of life vehicles, but it is generally consumed in the manufacture of steel for other sectors, most notably construction.

The recycled content of a typical vehicle is currently only about 20%, which is roughly true of the steel in a typical vehicle also. In Europe, the predominant route for manufacture of automotive steel is primary BF/BOS steel which has a recycled content of ~20%.

Why isn’t the recycled content of automotive steel higher?

There are three main reasons:

• Temperature control: When scrap is added to the BOS vessel during steelmaking, it cools down the molten iron with which it is mixed. While higher scrap contents could in principle be achieved, the temperature drop from adding 20% scrap is about the maximum that is usually tolerated.
• Steel cleanness: Automotive steels need to be very ‘clean’, i.e. be very low in residual element content, in order to achieve the mechanical properties needed. Whether for high formability or Ultra High Strength Steels (UHSS), low phosphorus and sulphur contents are required, and tramp elements such as copper and tin need to be kept to a minimum. Certain alloying elements must also be minimised, especially in high formability steels, including nickel, chromium, molybdenum and niobium. In fact for the future, we will want to separate types of steel scrap so as not to pollute the steel value stream.
• Zinc coatings: Zinc evaporates during steelmaking and is captured in the dust extraction system. This dust is a source of both iron and zinc, but at low zinc-contents it is of little use to zinc producers and it cannot be re-used in primary steelmaking facilities. Charging high quantities of zinc-coated scrap into an EAF furnace will result in a zinc-rich dust, but substantial dilution of scrap with, for example direct reduced iron (DRI) to meet cleanness targets, reduces the zinc content making it less attractive to zinc refiners.

Why isn’t more automotive scrap recycled in automotive steels ?

As a means to reduce CO2 emissions in steel manufacturing, higher recycled contents are beneficial, this is not in doubt – but does it have an impact on global CO2 emissions from the steel industry ?

As mentioned above, just about all steel from end of life vehicles is recycled. Often it is consumed in the manufacture of steel for other sectors, most notably construction. So the world is directly benefiting now from the reduced CO2 emissions derived from manufacturing steel from scrap. From a global perspective, it really doesn’t matter which sector benefits – provided all available scrap is used to manufacture new steel products, the world is benefiting. 

Currently, automotive steels are not manufactured solely from recycled steel. To meet stringent cleanness requirements, residual element contents are limited by careful scrap selection and dilution with purer iron sources such as direct reduced iron.

There is no reason why the automotive supply chain shouldn’t aspire to steels with higher recycled content provided the impact is understood. That is, while the automotive supply chain will be able to claim a greater share of already achieved CO2 emission savings, it won’t reduce global CO2 emissions.

What is perhaps more important is that we start on the path of recycling more automotive steel scrap into automotive steels with a view to enhancing the long term circularity of automotive steels and closing the product loop, by securing a supply of high quality scrap for the future.

?To be continued…

So, I have set the scene, but not completed the story. In my next blog I will describe in more detail how I believe the lag in ferrous scrap availability can be bridged by low carbon primary steelmaking and how the circularity of both steel and zinc can be enhanced.

If you are interested in this subject, want to find out more and ask questions, why not joint our free exclusive webinar on sustainability on the 25th February 2020.