Steel is a major building block of our modern world, used to make everything from cutlery to bridges and wind turbines. But the way it’s made – using coal – is making climate change worse.

On average, almost two tons of carbon dioxide (CO₂) are emitted for every ton of steel produced. This accounts for about 7 percent of global greenhouse gas emissions. Cleaning up steel production is clearly key to Earth’s low-carbon future.

Fortunately, a new path is emerging: so-called green steel, made using hydrogen rather than coal.

Steelmaking requires stripping oxygen from iron ore to produce pure iron metal. In traditional steelmaking, this is done using coal or natural gas in a process that releases CO₂. In green steel production, hydrogen made from renewable energy replaces fossil fuels.

Steelmaking is a complex process and is primarily achieved via one of three processes.

Blast furnace: Globally, about 70 percent of steel is produced using the blast furnace method. This coal-driven process leads to CO₂ emissions. It’s feasible to replace a portion of the carbon monoxide with hydrogen. The hydrogen can strip oxygen away from the ore, generating water instead of CO₂. This requires renewable electricity to produce green hydrogen.

Recycled steel: Around 30 percent of the world’s steel is made from recycled steel. Steel has one of the highest recycling rates of any material. Steel recycling is mainly done in arc furnaces, driven by electricity. Each ton of steel produced using this method produces about 0.4 tons of CO₂ — mostly due to emissions produced by burning fossil fuels for electricity generation. If the electricity was produced from renewable sources, the CO₂ output would be greatly reduced. But steel cannot continuously be recycled. After a while, unwanted elements such as copper, nickel and tin begin to accumulate in the steel, reducing its quality. Also, steel has a long lifetime and low turnover rate. This means recycled steel cannot meet all steel demand, and some new steel must be produced.

Direct reduced iron: This technology, DRI, often uses methane gas to produce hydrogen and carbon monoxide, which are then used to turn iron ore into iron. This method still creates CO₂ emissions and requires more electricity than the blast furnace method. However, its overall emission intensity can be substantially lower.

The green steel transition won’t happen overnight and significant challenges remain. Cheap, large-scale green hydrogen and renewable electricity will be required. And even if green hydrogen is used, to achieve net-zero emissions, the blast furnace method will still require carbon-capture and storage technologies — and so too will direct reduced iron technology, for the time being.

Private sector investment is needed to create a global-scale export industry.

Jessica Allen is a senior lecturer at University of Newcastle and wrote this story for The Conversation. Read the full article at this link: https://bit.ly/3wHwSCB