How Steel and concrete are climate change's hard problem

“DANGER” If anything, the sign beneath the dirty hunk of industrial machinery underplays things. When the 11-tonne slab of metal I’ve been watching emerges from the furnace, heated to 1300 °C, it glows incandescent white. Then it travels along a conveyor belt, hissing and steaming as it is cooled by water jets, before a line of rolling cylinders press it into the final product: a sheet of gleaming steel.

For all that we live in the digital age, we still rely on hot and dirty processes like this to construct our cities, homes and vehicles. Walking around the steelworks in Newport, UK, I get a sense of the immense energy required – and this is only the stage at which the steel is worked. Making it from raw iron ore is even more difficult. In fact, the production of steel and that other construction staple, concrete, accounts for as much as 16 per cent of humanity’s annual carbon dioxide emissions. That is equivalent to the carbon emission of the US.

In the fight against climate change, heavy industries are the final frontier. Decarbonizing transport and energy is the easy part. It is much harder to produce them without releasing enormous amount of CO₂ into the atmosphere. And yet, if we want to reach net-zero carbon targets, we can no longer ignore them.

Steel and iron production is reliant on coal, both as a feedstock and a fuel. Unlike cement, emissions arise at different points in the steel production process. Steel mills have a number of furnaces and subunits involved in the production process that emit carbon dioxide. The largest of these are the blast furnaces and the on-site power plant.

Steel production is an energy-intensive process, as it requires high temperatures to transform iron ore into steel. The energy and heat from the processes come from fossil fuels, which are primarily coal. The use of fossil fuels means that the average CO₂ emissions from steel production is about 1.85 tonnes CO₂ per tonne of steel produced. The best way to decarbonize existing steel plants is to use CCU on the blast furnace to capture and store or utilize the carbon dioxide. In some cases, this carbon dioxide can be utilized with water and a plant waste known as slag, to produce construction material. Valorization of captured carbon in this way can provide an additional revenue stream for steelmakers.

        The complexity of the steel production process provides a variety of challenges. The main challenge for steelworks is choosing the most effective site to install capture technology, as there are multiple emissions sources on-site. A number of solutions are possible to bring steel to net-zero.