There are Two Ways to Make Steel

The green economy is being built on steel. But many designers and specifiers don’t fully understand why the steel it’s built with matters.

From high-rise buildings and data centers to wind turbines and electric vehicles, steel will be a critical component for building a sustainable future. Yet today, the steel industry contributes around 8% of global CO2 emissions. A truly green economy will be one built with green, low-embodied-carbon steel. That’s why it is essential to understand that there are two ways to make steel – extractive and circular – which yield significantly different greenhouse gas (GHG) intensities embodied in the steel they produce.

Extractive Steelmaking

Blast Furnace / Basic Oxygen Furnace

A typical blast furnace used by an extractive steel mill.

The extractive steelmaking process, also known as integrated steelmaking, is the traditional method for producing steel. It starts with mining raw materials out of the ground, including iron ore, limestone, and coal. These materials are melted in an energy-intensive blast furnace (BF), which reacts iron oxide and carbon (in the form of coke) to form two products: iron (saturated with carbon) and CO2. Liquid iron from the blast furnace is then reacted with oxygen in a second step via a basic oxygen furnace (BOF) to remove excess carbon, producing even more CO2. This reduced form of iron is steel.

The extractive process is particularly emissions-heavy because CO2 is a byproduct of both steps along the way – the blast furnace and the basic oxygen furnace. Furthermore, the process always requires the extraction of natural resources from the earth. While the extractive method of steelmaking has been used for hundreds of years and remains widespread, a modern and significantly more sustainable process is available – circular steelmaking.

Circular Steelmaking

Electric Arc Furnace

One of Nucor’s circular EAF steel mills.

Nucor’s circular steelmaking process starts with recycling steel from end-of-life scrap collected from things like decommissioned buildings, old cars and appliances, and waste collected from fabricators and stampers. This scrap is melted using electricity in an electric arc furnace (EAF) to create new high-quality steel. The use of scrap eliminates the need for the series of chemical reactions in a BF-BOF that produce high amounts of CO2. The process becomes circular when steel products come to the end of their useful life: Nucor buys the scrap to recycle again into new steel. This cycle can continue infinitely without any loss in steel quality.

The circular steelmaking process is significantly less emissions-intensive and more sustainable than the extractive process. By recycling scrap instead of mining raw materials, the circular process keeps carbon-rich materials in the ground – conserving natural resources – and mitigates the emissions associated with mining and both blast and basic oxygen furnaces. Using electricity for energy instead of coal combustion is much cleaner, and if electricity from renewable energy sources is combined with high percentages of scrap usage, the carbon footprint of this process drops almost to zero.

Head-to-Head

Comparing GHG Intensities for Steelmaking

The difference in inputs and processes between the BF-BOF (extractive) and EAF (circular) steelmaking methods results in a significant difference in total CO2 emissions. The BF-BOF process, on average, emits 2.32 tons of CO2 for every ton of steel produced for Scopes 1-3. In comparison, Nucor’s EAF process emits only 0.76 tons of CO2 per ton of steel produced for Scopes 1-3. This means that the source of steel for a project can impact a project’s carbon footprint in a significant way.

For example, the automotive industry is expected to put 350 million electric vehicles (EV) on the road by 2030, with each EV requiring about 1 ton of steel. If these EV’s are built with extractive steel, about 812 million tons of CO2 will be emitted to produce the required steel. However, if circular steel is used, only about 266 million tons of CO2 will be emitted to produce the necessary steel. That’s a staggering differential of 546 million tons of CO2 emissions mitigated by using circular EAF steel.

Nucor is a Leader in Sustainable Steelmaking and Industrial Decarbonization

Today, Nucor is North America’s largest steel producer and recycler. For more than 50 years, we’ve pioneered circular steelmaking, starting with our first EAF mill in 1969. Since that time, Nucor has never used traditional blast-furnace technology – all of our mills use EAFs to make steel the sustainable way.

But we’re not stopping there. Nucor is committed to net-zero, science-based greenhouse gas targets for 2050, which includes Scopes 1, 2 & 3. We are continuing to drive our industry forward through carbon-reduction technology and innovations like carbon capture and storage (CCS). CCS is a technology that can greatly reduce the net carbon footprint of direct reduced iron (DRI), a steelmaking input. Nucor is also investing in carbon reduction initiatives like [small modular reactors](https://nucor.com/madeforgood/nuscale-case-study) (SMR) that could provide carbon-free electricity to its mills, and green pig iron – also a steelmaking input – produced from biochar. Projects like these will allow Nucor to continue increasing the sustainability of its operations and advance the decarbonization of our industry.

The green economy is in motion, and it will require a reliable supply of high-quality, sustainably made steel to ensure its success.

Curious how circular steel can help you reach your sustainability goals?