Blog: What we mean when we talk about low-carbon steel

Andrew Purvis

Director, Safety, Environment and Technology, worldsteel

12 April 2021

Nicholas Walters

Director, Communications and Public Policy, worldsteel

12 April 2021

Our industry’s history in many ways reflects the societies in which we operate, and since the industrial revolution, iron and steel production has been powered by coal. 

This is now changing, and the steel industry, like the rest of society, is transforming to provide products and services in a future in which the emission of carbon dioxide and other greenhouse gases is severely curtailed.  

The language associated with this shift is still developing, and consequently, a wide variety of expressions are being used by different stakeholders. 

These expressions are often used interchangeably but can sometimes mean hugely different things. What are we to make of the increasingly varied use of the expression green steel? To some, it is simply a marketing term with no definition or boundary.

At the other extreme, some believe it is a term needing certification covering the breadth of the whole realm of sustainability.

And the problem is not just with green steel. Is my green steel your clean steel or zero-carbon steel? And where are the lines drawn between net-zero steel, zero-carbon steel and low-carbon steel? 

At worldsteel, we are putting in place some definitions that will provide clarity on what we mean when we talk about these topics.

Our industry and our members are working to develop and launch a new family of steel products, produced with a much lower carbon burden than in the past.

This low-carbon steel is manufactured using technologies and practices that result in the emission of significantly lower emissions than conventional production.

In 2021 most steel is produced using fossil fuel-based reductants; however, many steelmakers have implemented, or are developing, technologies that significantly reduce emissions from the core steelmaking process. Examples include:

  • Aço Verde do Brasil is using 100% charcoal to produce low carbon iron and steel products.
  • ArcelorMittal is constructing a large-scale facility in Ghent, Belgium to convert steel plant waste gases to ethanol, which can be used in a wide range of applications, including the production of synthetic fuels. A similar commercial facility began operation in 2018 at Shougang Steel in China, producing 30 million litres of ethanol for sale in the first year of operation.
  • At Emirates Steel in the United Arab Emirates up to 800kt of CO2 per year is captured from the CO2 rich gas stream from the ironmaking plant before being injected into a mature oil field for permanent storage
  • EVRAZ’s Rocky Mountain Steel in Colorado is transitioning from coal to solar. The EVRAZ plant will be the largest on-site solar plant in the country dedicated to a single customer.
  • HBIS, a leading Chinese steelmaker, is building a 1.2Mt capacity hydrogen metallurgy DRI demonstration project. The project will use green and blue hydrogen technologies to explore a path to zero CO2 emissions from the iron and steel making process. 
  • Nucor’s micro mill in Sedalia, Missouri, is the first U.S. steel plant to run on wind energy. The plant is a partnership between the steel company and local utility, which will power the plant after a power purchase agreement between the companies.
  • Tata Steel is developing innovative new smelting technology through their HIsarna project.  HIsarna technology can produce iron without coke ovens, or agglomeration facilities, producing a CO2 rich waste gas stream ideally suited to CCS.
  • thyssenkrupp Steel and Nippon Steel Corporation have launched a series of tests into the use of hydrogen in a working blast furnace, aimed at significantly reducing the CO2 emissions arising during steelmaking. 

Steel produced using all these technologies can be considered as low-carbon steel, though it is likely that what is considered low-carbon steel now may be different by 2050 when regulation, societal expectations and technologies have completely changed.

Many other expressions are used within our industry and by stakeholders to refer to steel produced using these next-generation production technologies.  

worldsteel prefers and uses low-carbon steel as, like ‘low-carbon electricity', we feel it is intuitively easier to understand and its meaning is clear.

Green steel is being used and interpreted by many different parties to mean different things, often in the context of marketing new more environmentally conscious products. It has been used to refer to steel manufactured using breakthrough technology, steel produced from scrap, reused and remanufactured steel, and conventional steel with emissions offset through the retirement of carbon units or allowances. Given this inherent lack of clarity and diversity of meanings ‘green steel’ is not an expression worldsteel uses.

To be truly zero-carbon, steel would need to be produced without any CO2 emissions at all. This is a very high bar to reach, and it is difficult to conceive of a production technology that could achieve this in 2021. 

Many may be moving towards this, but zero is absolute, and probably unachievable without the use of offsets for residual carbon emissions. These residual emissions may arise in the supply chain, from the use of carbon-bearing electrodes or the use of natural gas in associated processes. 

Ultimately steel needs to contain some carbon, as this is what differentiates it from pure iron. While this essential alloying carbon can be sourced from non-fossil sources, its presence makes ‘zero-carbon’ steel something of a misnomer.

If, however, a balance can be achieved between the greenhouse gases put into the atmosphere when producing steel and emissions taken out of the atmosphere by sinks, the resulting steel can be referred to as net-zero, or carbon-neutral steel

The production of net-zero steel may require offsets in other sectors to achieve true neutrality, and it is important that if claims of carbon neutrality are made producers are transparent about boundaries, their accounting methodologies, and the quality and credibility of any offsets used.

A few steel companies are beginning to market fossil-free steel. Fossil-free steel is steel manufactured without using any fossil fuels such as coal or natural gas, nor any fossil fuel-derived energy. 

All fossil-free steel will be low-carbon, but not all low-carbon steel can be described as fossil-free. For example, low-carbon steel produced in a facility employing carbon capture and storage (CCS) may well still use natural gas or coal, but prevent the emission of CO2 to atmosphere. If biomass plays a role, it will be important to ensure it is responsibly sourced[1].

Clean steel is a technical expression used in the steel sector to refer to steels containing low levels of impurities, oxides, inclusions, or low or ultra-low level of carbon dissolved in the metal. The phrase is in common use, including by worldsteel in our 2004 ‘Study on Clean Steel’, and means something specific. As such worldsteel does not refer to “clean steel” in the context of climate change.

Carbon-free is also a difficult expression to relate to steel, after all, steel without carbon is iron, and the carbon content of steel is precisely controlled to achieve the properties demanded in a specific batch.  Carbon will need to be added to hydrogen reduced iron in order to turn it into steel through the refining process

The climate change conversation is often conducted in terms of the need to decarbonise society.  worldsteel does not generally use this expression to refer to steel production, as it is the emissions from steel production that need to be free of GHGs/CO2, not the process itself. 

Many promising breakthrough technologies will still use carbon as a chemical reducing agent but prevent harmful GHGs from being released into the atmosphere. So, while the emissions from our industry will ultimately be decarbonised, the ironmaking process itself may not be.

Breakthrough technology produces low-carbon steel in a radically different way to the conventional blast furnace, DRI or EAF technology. Examples of breakthrough technology being developed include hydrogen reduction, the application of CCS, the electrolysis of iron ore, a suite of carbon capture usage and storage (CCUS) technologies and new smelting reduction processes.

Hydrogen is a key vector that will allow GHG emissions from the iron and steel sector to be significantly reduced, and many of worldsteel’s members are exploring this technology option. Hydrogen is often attributed a colour, depending on its low-carbon credentials.

When worldsteel talks about low carbon hydrogen, we mean:

  • Green hydrogen is produced through the electrolysis of water, powered by renewable electricity.
  • Blue hydrogen is made from natural gas through the process of steam methane reforming combined with CCS.
  • Hydrogen can also be produced using electrolysis using other sources of low-carbon electricity, such as nuclear or CCS. We also consider this to be low-carbon.

Fossil hydrogen is made from unabated fossil fuels, chiefly:

  • Grey hydrogen is made from natural gas through the process of steam methane reforming, without CCS so CO2 is emitted to atmosphere.
  • Brown, or black hydrogen is manufactured through coal gasification and leads to significantly higher GHG emissions than other hues.

step up is worldsteel’s 4-stage efficiency review process. step up aims to improve the efficiency of steel production now, to support our members in operating their sites at a level of performance commensurate with the world’s most efficient sites. step up is a transitional programme and should not be seen as providing a solution to the steel industry’s climate change challenges.

[1] A number of schemes exist to certify responsible biomass, for example, the Forestry Stewardship Council 

Add your comment here:

  • 1

    This is particularly important, as a definition of green steel/ low carbon steel will be needed in the near future, if as expected, legislation will be required to drive change and associated value.

    avatarAndrew DunsmoreApr 12, 2021, 3:43:59 PMReply

  • 2

    Renewable carbon from biomass is a zero emissions carbon with added chemical and has social and environmental benefits. It must be considered as the carburizer of choice for the almost zero emissions steels!

    avatarRonaldo sampaioApr 12, 2021, 9:08:25 PMReply

  • 3

    Green hydrogen is suitable to address the low carbon steel and climate change low emission of co2 gases. We have to think of the application of low carbon steel and zero carbon emission technology.

    avatarGouranga RoutApr 13, 2021, 4:58:42 AMReply

  • 4

    The production of steel, without carbon, is a very difficult proposition, but yes carbon content needs to be brought down as far as possible. Presently in India, not much effort is being made in this regard. The adoption of EAF routes using recycled steel can be a better alternative for the time being.

    avatarMr. DEOKUMAR GHATAKMay 6, 2021, 6:08:15 PMReply

  • 5

    Scrap plays a key role in supressing industry emissions and resource consumption, and in theory, all new steel could be made from recycled steel. However, currently, this is not feasible due to the scarcity of scrap. The average life of steel products ranges from a few weeks for steel packaging to up to 100 years for buildings and infrastructure. This means there is a significant delay between steel being produced and being available for recycling, and continued growth in steel demand means that transitioning the industry to entirely scrap based production is unlikely to be possible during this century. So, while scrap used in the EAF and BF route will play a key role in reducing emissions, new virgin steel will continue to be required for the foreseeable future, and the emissions from this material will need to be addressed.

    avatarAndrew PurvisJun 3, 2021, 2:45:44 PMReply

  • 6

    Low carbon steel is used to describe steel with C content of less than 0.3%. So your use of the term is neither intuitively easy to understand nor is its meaning clear, rather it is highly ambiguous as it overturns many, many years of previous use of the term to describe something quite different (see refs below).

    https://en.wikipedia.org/wiki/Carbon_steel#Mild_or_low-carbon_steel https://www.sciencedirect.com/topics/materials-science/low-carbon-steel

    avatarRod Vanstone CEng FIMMMMay 12, 2021, 1:24:02 PMReply

  • 7

    Whiles it is true that "low carbon steel" has a distinct metallurgical meaning, we use lots of terms inside the industry that are not used outside, like 'clean steel' which is mentioned in the blog. There is no perfect expression, but when we use the expression “low carbon steel” in this context we are largely addressing a constituency outside of our industry, in that context we feel 'low carbon steel' fits well with “low carbon electricity”, “low carbon buildings” etc.

    avatarAndrew PurvisJun 3, 2021, 2:39:31 PMReply

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