Iron and steel production is a dirty business – or at least it has been historically.
By various measures, the business of mining and processing iron makes up 7% of the global carbon dioxide emissions. Turning iron into steel is figured to contribute 1.8 tons of CO2 for every ton of steel produced, including the iron ore share.
Given that most of the production of steel globally is done through a variant of technology which dates back to the late 1800s, this is not very surprising. It is no accident that blast furnaces are called by that name.
The author recalls standing on a rise above one of the Krupp steel mills near Essen, Germany on a night in the 1980s, watching, from a safe distance, as pure oxygen was jetted across the lava hot iron; the sheet of flame that resulted lit up the countryside around the plant. It was a memorable sight to see. This industrial light show took place several times a day, every day, week in, week out, all year long, for decades.
Melting iron ore at 1800° C, which is what I was watching happen, generates lots of carbon dioxide. And that has become a problem in a society wanting to reduce greenhouse gasses.
The modern world is literally built of steel. Every piece of infrastructure, almost all vehicles that roll on land or float on the sea are mainly made of some kind of steel; any vertical structure of any size has large amounts of steel in it – buildings, walls, dams are huge steel users, as are things as basic as furniture. The desk the computer is sitting on as this article is being written is made of steel.
Since there is fundamentally no other material that offer the combination of virtues of steel, it is necessary to find ways to reduce the environmental impact of this vital and irreplaceable material.
In specific terms, the goal is to halve the carbon dioxide emissions of the global steel industry by 2030. No one pretends that this is going to be an easy thing to accomplish, and it is taken as given that a number of steel plants will not be able to reduce their emissions enough to stay open.
There are a couple of main technological tracks in steel production that are being followed to achieve the large reduction in carbon spewed into the atmosphere by the industry.
One is to convert many steel plants from direct oxygen blast furnaces (such as I saw in Essen) to electric arc furnaces.
Electric arc furnaces “cook” metal with heat, but no combustion, using a sustained “arc” from electric current through giant anodes to create enough heat to melt scrap steel, which is mixed with with pre-treated iron known as hot briquette iron (HBI). Carbon is added to the melted metal, and the result is new steel for rolling, shaping and forming.
The drawbacks of electric arc furnaces include that they need a supply of scrap steel as part of their feedstock, and scrap steel is expensive to transport long distances, so will always be supply constrained. To be really reducing carbon emissions with electric arc furnaces, the way HBI is made becomes a major element in the evaluation of the whole supply chain. Also they consume vast amounts of electricity, so the carbon emissions of the power generation are a factor in making these plants genuinely “green”
Several North American and European steel mills are adding electric arc operations and shuttering old blast furnaces. This is easier to do in those plants, because many of be blast furnaces are close to the end of their economic life. In China, which produces half of all the steel made in the world today, many of their steel mills are much newer, and the blast furnaces, which are a very large capital item, are not close to an age where they are ready to be closed and replaced. How this will be resolved is not certain at the moment.
Another track is a modern technology which is somewhat closer to that of traditional blast furnaces. This method can run on high grade iron ore, but the heat is supplied by burning hydrogen, which does not create any CO2. This is called direct reduction iron (DRI).
In a direct reduction plant, the iron ore has impurities burned out of it, as with blast furnaces, but not using coal as the combustion mechanism, as in the old technology plants.
DRI has a number of good features, but “green” hydrogen production – not using any fossil fuels – is still expensive, and “dirty” hydrogen, from natural gas reforming, is a significant CO2 producer-
which cancels out a large part of the greenhouse gas reductions that are being sought.
There are a number of projects to find technological breakthroughs in steel production – in northern Sweden a hydrogen based DRI steel mill is taking shape, with the hydrogen coming from electrolysis of water – separating the water into hydrogen atoms and oxygen atoms by running an electric current through them. The electricity comes from a nearby hydroelectric power plant, so the process is quite “green.”
The Swedish company, H2 Steel, has already produced samples of hydrogen fired steel, and will be in production in 2026, with plans to be producing five million tons of steel per year by 2030.
In Canada and the US there are several projects – in various stages – to produce HBI with minimal carbon dioxide released. One, by Strategic Resources in Quebec, would be initially a natural gas fired HBI plant, which would capture and store the CO2, but the plant is designed to be able to convert to being hydrogen fired at a later date, when cost competitive hydrogen production technology has arrived.
In conclusion, the reduction in the carbon intensity of the iron and steel business is happening now. The fact that there are issues to resolve, and problems to overcome, is something that would be true with any major industry going through a technological transition. No perfect solution for “zero emission” steel is likely, but the industry will get steadily better at limiting its greenhouse gas output over time. Given the history and origins of the steel industry, this is a major step forward. Its a little like Samuel Johnson said about a dog walking on its hind legs “it isn’t that this is done badly that is remarkable, but the fact that it can be done at all.”
14.11.2023