Carbon footprint of global steel production remains high: ‘Capturing CO₂ won’t solve it’
Steel production is likely to take up a large portion of our future carbon budget. Capturing CO₂ from coal-based production won’t solve the problem. Technologies that rely on renewables are more effective, but not enough to get to net zero.
The production of iron and steel causes 7 to 9 percent of global greenhouse gases. But that share might increase in the future, as steel demand is expected to rise due to construction in emerging economies.
About 75 percent of steel is currently made in blast furnaces, which rely heavily on coal. This generates large amounts of carbon emissions. These could be reduced with new technologies that use green hydrogen or electricity (so-called electrowinning).
Even the most optimistic scenario fails to meet climate targets
Until now, no study had examined the future impacts of steel production while taking these new technologies into account. That’s what Carina Harpprecht did. She is a Leiden PhD candidate and scientist at the German Aerospace Center. Harpprecht calculated the industry’s global emissions under three different scenarios: an ambitious scenario consistent with limiting global warming to 1.5 degree. And two other scenarios in which the global temperature rises to below 2 degrees and to 3.5 degrees.
Strikingly, the reduction of CO₂ emissions from global iron and steel production is insufficient to meet climate targets even in the first, most optimistic scenario. By 2060, the sector alone would consume 18 to 30 percent of the carbon budget left until 2100. That ‘budget’ is the maximum amount of CO₂ that can be emitted while limiting global warming to 1.5 degree.
Are technologies based on renewables the solution?
Electricity-based technologies can make a major difference. ‘Using hydrogen or electrowinning could cut greenhouse-gas emissions by up to 95 percent per ton of steel by 2060 compared with today’s methods,’ Harpprecht says. This assumes that electricity and hydrogen come from renewable sources. However, adopting these new technologies on a large scale requires time, major investments, and new infrastructure. It will take 10 to 15 years before electrowinning is ready for industrial-scale production.
‘Steelmaking is one of the most promising hydrogen applications.’
Capturing carbon, replacing coal or switching to new technologies
One technology Harpprecht disapproves of for lowering CO₂ emissions is Carbon Capture and Storage (CCS). This means carbon is captured at the furnace and then stored, often underground. ‘This only helps in the short term,’ she says. Retrofitting existing plants with CCS can lower emissions up to 55 percent. ‘But for the net-zero target, the reduction is insufficient.’
CCS also risks a so-called lock-in effect, Harpprecht argues. ‘Once the infrastructure is built, it’s usually operated for twenty years or longer.’ It would be better to replace coal-based furnaces with natural-gas-based ones, the research shows. ‘Natural gas has a much lower emission intensity and these furnaces can shift to hydrogen later.’
Apart from switching to new technologies, reducing demand for primary steel would be highly effective, according to Harpprecht. Using less primary steel and more recycled steel could lead to larger emission reductions than those in the scenarios.
Hydrogen very promising in the production of steel
Harpprecht’s finding that even the best scenario doesn’t suffice for the 1.5 degree target does not mean decarbonising the steel industry is futile. On the contrary: its potential is huge. The industry is even one of the best suited to adopt hydrogen, Harpprecht and colleagues show.
‘Steelmaking is one of the most promising hydrogen applications,’ says lead author of that paper, Tom Terlouw, scientist at the Paul Scherrer Institute in Switzerland. ‘This is because of a lack of alternatives. Transport, for example, has other options than hydrogen, such as electrification.’
Future environmental impacts of global iron and steel production was published in Energy & Environmental Science on June 27.
Global greenhouse gas emissions mitigation potential of existing and planned hydrogen projects was published in Nature Energy on November 6.