Technologies and strategies across several areas can help to reduce the carbon footprint of the world’s steel industry, a webinar has heard.

During an online session hosted by the Council on Vertical Urbanism (CVU) and constructsteel – a global construction market development program hosted by the World Steel Association – Dr Olivier Vassart, chairman of constructsteel, gave an overview of strategies and technologies which can help to reduce the steel industry’s carbon footprint over the median term.

The presentation was followed by a panel session. This included Terrance Busuttil, Director of constructsteel; Pascal Lameroi, Project Lead Communication at ArcelorMittal Steligence; Mark Wooseok Kim, Senior researcher in design solutions at South Korean steel manufacturer POSCO; and Cenira de Moura Nunes, general manager and global head of environment for Gedo in Brazil.

The session was moderated by Shonn Mills, chair of the board of trustees at CVU.

The discussion comes as both the construction sector generally and the steel industry specifically face a need to reduce the carbon and environmental footprint of their operations.

Worldwide, the built environment contributes around 40 percent of global carbon emissions (refer webinar recording for references contained in this article).

Meanwhile, the iron and steel industry specifically contributes around 7 to 9 percent of global carbon emissions.

On average, the steel industry emits 2.0 tonnes of carbon for every tonne of steel produced. This results in overall emissions of about 3.3 billion tonnes of CO2 each year.

With just over half (52 percent) of the volume of all steel worldwide going into buildings and infrastructure, the built environment has a significant role to play in steel industry decarbonisation.

(This 13-storey commercial office building in London’s Farringdon Street achieved an overall embodied carbon dioxide emission footprint for the entire steel structure of just 67kg per square meter. Around 87 tonned of resused steel columns were used on the project whilst 60 percent of material used was low-carbon steel made through an electric arc furnace with recycled scrap feedstock.)

Two streams of decarbonisation

According to Vassart, decarbonisation strategies can be considered in two streams.

These are:

• technological innovations to reduce emission intensity of the steel making processes; and
• design strategies to reduce emissions across the lifecycle of buildings and infrastructure.

In terms of steel production, a key strategy which is available today involves turning recycled steel into steel products using an electric arc furnace (EAF).

As things stand, steel production occurs through two main methods.

First, there is Basic Oxygen Furnace (BOF) method. This involves producing ‘virgin’ steel from extracted iron ore using coal-based blast furnaces.

Currently, 71 percent of all steel products are made using this method worldwide.

However, this process is emissions intensive as significant amounts of carbon dioxide are emitted during the process in which metallurgical coke (derived from coal) is used to strip oxygen from iron ore. Additional CO2 emissions occur where fossil fuels are used to supply energy to generate the intense heat (above 1,500 degrees Celsius) which is required for this process.

As a result, each tonne of steel produced through BOF emits an average 2.33 tonnes of carbon dioxide.

An alternative is to produce recycled steel products using an electric arc furnace.

This method uses high-voltage, high-current electricity to heat and melt recycled scrap products. It is primarily geared toward the use of recycled steel using scrap metal.

Generally, this method has a lower emissions profile compared with BOF as it does not require the burning of fossil fuels during the production process.

Instead, the primary source of carbon emissions involves the use of electricity during the process.

On a global average basis, recycled steel produced using EAF emits 0.68 tonnes of carbon dioxide for each tonne of steel which is produced (emissions vary according to location and access to clean energy for the process). This is about four times less than the emissions profile which is associated with BOF.

Currently, the global share of production which is made using electric arc furnace stands at 28.6 percent.

(an electric arc furnace)

Whilst EAF seems like a good idea, Vassart says that a limitation involves the supply of second-hand steel to be used as feedstock in production.

Whilst scrap availability is high across mature markets Europe, North America and Japan, it remains constrained in places such as China – where more than half of the world’s steel in produced.

Whilst EAF is geared toward recycled steel, one method of making virgin steel with a lower carbon content is known as direct reduced iron (DRI).

Whereas traditional BOF relies upon the burning of coal, with DRI, this is replaced with either natural gas or hydrogen.

Where natural gas is used, the average carbon intensity of the steel production process falls to 1.37 tonnes of CO2 per tonne of steel produced. This represents emission savings of nearly half compared with BOF.

In the future, further emission reductions may be possible through use of hydrogen rather than natural gas (presuming that the hydrogen is produced using clean energy).

This will make it possible to produce near-zero emission steel, with a CO2 content of as low as 0.1 to 0.4 tonnes per tonne of steel produced.

Currently, development of hydrogen based DRI technologies remain at the demonstration stage.

Several pilot projects are underway. Commercial deployment of these may occur from 2030 to 2035 onwards.

Other current and future promising technologies include:

• Making virgin steel through direct electrolysis of iron ore, a process through which electrons are added to iron ore in order to produce iron and oxygen. This avoids the need for use of coal or gas. These technologies are currently scaling up. Commercialisation is possible after 2035.
• Carbon capture. Already in widespread use, this involves the capture of carbon that is produced when either BOF or DRI is used. Captured carbon is transported and stored either in the ground or in above-ground carbon mineralisation which is then used for construction materials. According to Vassart, as many as 80 to 95 percent of CO2 emissions can be captured and stored.
• Replacing a portion of the fossil fuels used in steel production with biomass and waste-based technologies. For example, solid biomass such as wood waste or forest residues can be processed into charcoal or biocarbon to replace a portion of the metallurgical coal that is used to reduce iron ore in blast furnaces.

(Using an electric arc furnace, steel can be produced with four times less carbon compared with a traditional basic oxygen furnace.)

Better building and infrastructure design

In addition to aforementioned technologies, Vassart encourages architects and engineers to consider strategies to reduce the emissions profile of new buildings and infrastructure.

To do this, it is important to think carefully about material choices during early project stages of planning and engineering design.

Potential strategies include:

• Using less steel through optimising topology design, using high-strength steel, using lightweight structural systems and use of modular or prefabricated design.
• Adopting circular economy methods such as reuse and recycling, design for disassembly, reuse of structural components and closed loop recyclability.

According to Vassart, the importance of these strategies should not be underestimated.

Take, for example, the use of high-strength steel.

Granted, Vassart acknowledges that this is on average 25 percent more expensive on a per tonne basis compared with regular steel (refer presentation for source).

However, he says that high-strength steel saves costs overall on account of fewer tonnes of steel being needed for each building component along with lower welding costs.

Meanwhile, by achieving average weight reductions of around 30 percent, high-strength steel delivers carbon emission savings of approximately 30 percent. This is achieved by simply using less material.

Kim agrees. He adds that high strength steel can deliver two other advantages.

First, due to its structural stability, high-strength steel can deliver greater design flexibility.

In particular, high-strength steel can enable greater spacing between columns, a reduction in the number of columns which are needed and a reduction in floor slab space which is needed. In turn, this can enable wider spans, higher ceilings and greater floor to ceiling space. The result is more natural light, better interior spatial quality and improved aesthetic value.

Outside the building, high-strength steel can enable thinner panels to be manufactured and installed on large facades. This delivers savings in terms of material usage and weight reduction.

The second benefit is durability.

By providing long-term structural rigidity, high-strength steel extends the lifespan of buildings and reduces the need for reconstruction and major repairs. (In turn, this further helps to minimise the structure’s environmental impact over its life cycle.)

(image source: constructsteel)

Case studies

During his presentation, Vassart highlighted several case studies.

One is a 13-storey commercial office in London’s Farringdon Street.

This achieved an overall embodied carbon dioxide emission footprint for the entire steel structure of just 67 kg per square meter.

Around 87 tonnes of reused steel columns were used on the project, with embodied carbon emission of just 46 kg of CO2 per square meter.

Furthermore, 60 percent of the total material procured was low-embodied carbon steel that was made through EOF using 100 percent renewable energy and 100 percent scrap material.

Another example is the refurbishment of the entire façade of the five storey Hanwha Galleria department store in Gwanggyo south of the South Korean capital of Seoul.

Under the original plan, 3mm thick aluminium was set to be used as the façade material.

By applying parametric design to optimise structural stability, this was replaced with 1.2 mm thick low carbon high-strength steel.

This delivered embodied carbon savings of 86 percent compared with the original design.

(Hanwha Galleria, Gwangyo, South Korea)

Key role for the construction sector

Finally, Vassart encourages architects, engineers and the construction industry to play a proactive role.

In addition to aforementioned measures, this involves advocating for low carbon steel in policies and projects.

“This is not science fiction, the steel is available,” Vassart said.

“These low emitting carbon steel products do exist. The more you use them, the more you will decrease the emitted carbon of your buildings.

“The global steel industry is committed to decreasing its carbon intensity. We are acting at three levels: energy efficiency, maximising recycling and developing breakthrough technologies.

“Today, the low emission carbon steel is available. It will of course vary depending on the region. We need to have access to low carbon energy. We need the infrastructure for storage and transport. And of course, we need the market demand. We need you to use these types of steel.

“The construction can already achieve a lot of gains through design efficiency and circularity.

“We are asking you and helping you to support the different policies that will foster the demand for low carbon steel.”

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