Green Steel | SMaRT@UNSW (2024)

FAQs

What is the chemistry behind green steel? ›

The process works by introducing hydrogen gas into the reactor vessel, along with iron oxide in the form of iron ore pellets or fines. The hydrogen gas acts as a reducing agent, meaning it donates electrons to the iron oxide and causes it to lose oxygen atoms and become metallic iron.

More on SSAB Fossil-free™ steel

SSAB Fossil-free™ steel is produced using the revolutionary HYBRIT^® technology, which replaces coal in the iron ore reduction process with hydrogen.

Green steel production, with its focus on renewable energy and resource conservation, can help improve air and water quality and reduce the negative impacts on human health and the environment.

Sustainability: Green steel production reduces the environmental impact of steel production and helps to make it more sustainable. This includes reducing carbon emissions, reducing the use of non-renewable energy sources, and minimising waste.

For one ton of crude steel produced from iron ore, the hydrogen generation requires 2,633 kWh of power, and in addition, the direct reduction and EAF plants consume 816 kWh.

One kilogram of hydrogen produced via electrolysis requires 50-55 kWh electricity. Manufacturing 1 ton of steel needs 50 kg of hydrogen.

There is also at least one type of stainless steel (H1) which is precipitation hardened and contains nitrogen instead of carbon. This is a different hardening mechanism to that of carbon steel. The purpose of eliminating carbon is to improve corrosion resistance, especially in salt water.

For technical reasons, green steel making requires the 'electric arc furnace' route; EAFs need high-grade ores, in which iron content is over 60 per cent.

A supercharged — and low-carbon — grid

Boston Metal says that its technology uses 4 megawatt-hours of electricity to produce 1 ton of steel. That's enough to power the average U.S. home for more than four months.

Non-ferrous metals are used for a wide range of commercial, industrial and residential applications. Some, such as aluminium or titanium alloys, can replace steel. However, they are often more expensive and are better employed for their specific attributes.

Can green steel be recycled? ›

Steel can be infinitely recycled without losing any of its properties in a fully electric process that gives off few emissions. This is one solution for reducing its environmental impact in the throes of the fight against climate change.

Professor Veena Sahajwalla has pioneered research into waste – turning it into new green materials and products. She is best known for her invention of 'green steel' technology, which uses carbon extracted from old tyres to replace coal or co*ke in steel manufacturing.

While the technology exists to create green steel — using hydrogen produced from renewable electricity — some challenges must still be overcome before this nascent process can be scaled up. And the main barrier is the vast amounts of green and blue hydrogen required.

Ultimately, the most environmentally friendly materials are corrosion resistant and durable, have high-recycled content and recapture rates, provide long service life and reduce resource use. Stainless steel provides all of these benefits.

As far as building materials go, steel is one of the most sustainable. It is not only environmentally conscious but economically strategic in its inherent longevity and durability. Steel is the most recycled material in the world. More steel is recycled each year than aluminum, paper, glass and plastic combined.

For example, some stainless steel alloys contain metal elements such as copper, iron, and zinc. These elements may form compounds with chromium, which will destroy the oxide film on the surface of the stainless steel and cause greening.

The greenest alternative is to use hydrogen to reduce the iron ore to iron, producing only water as a byproduct. This process isn't entirely new – a few factories already reduce iron ore with hydrogen and carbon monoxide derived from natural gas.

But what does this buzzword actually mean? As of today, there is no universally accepted definition for it and it is mostly used to describe steel products that embody some form of more sustainable production (e.g., high recycling rate or green energy usage).

By reacting hydrogen directly with iron ore, iron and water are produced in place of iron and CO₂. This process is called Direct Reduced Iron (DRI) and is already being used with natural gas instead of hydrogen.