DLR study examines the decarbonisation of the global steel industry

Using various scenarios, the DLR has investigated how greenhouse gas emissions from global iron and steel production can be reduced. The researchers looked at carbon capture and storage (CCS), the use of hydrogen and the electrified production of iron. The results show that the emission reductions achieved through CCS in coal-based plants are insufficient in the long term to meet climate targets. Hydrogen-based and electrified technologies using green electricity, on the other hand, represent the key technologies.

The German Aerospace Centre (DLR) has conducted a study examining how the global steel industry can significantly reduce its CO₂ emissions. This is a key starting point in the fight against global warming. This is because the production of iron and steel accounts for around nine per cent of global greenhouse gas emissions. In their study, researchers at the DLR Institute of Networked Energy Systems analysed, using several scenarios, how the introduction of new technologies could affect greenhouse gas emissions from global iron and steel production. The focus is on three technologies: carbon capture and storage (CCS), the use of hydrogen, and the electricity-based production of iron.
“The study shows that comprehensive and far-reaching measures – supported by a political framework at international level – are needed in the near future. This is the only way to drive forward the decarbonisation of the steel industry sufficiently whilst taking into account competitiveness in Germany and Europe. A fundamental prerequisite is also the rapid and massive expansion of electricity generation from renewable sources,” summarises Prof. Meike Jipp, DLR Executive Board Member for Energy and Transport. “This is also against the backdrop that, due to the EU Emissions Trading Scheme, the costs of CO₂ emissions will rise gradually in future, thereby making existing production processes more expensive. It is therefore essential to create incentives for new technologies now and to implement them.”

CO₂ capture and storage is not enough

Steel is produced in blast furnaces. Coke, a special type of coal, is the primary energy source used. CO₂ emissions from steel production are correspondingly high: between 1.6 and 2.2 tonnes of CO₂ are produced per tonne of steel. Retrofitting existing blast furnaces with technologies that capture and store CO₂ can significantly reduce CO₂ emissions. “Our analysis shows that these technologies can reduce emissions in the short term, as CCS enables the retrofitting of modern existing plants. In the long term, however, the emission reduction potential of CCS is insufficient,” concludes DLR researcher Carina Harpprecht. She produced the DLR study together with colleagues from the Energy Systems Analysis Department. “The electrification of the production process is the key strategy for achieving far-reaching reductions in emissions,” Harpprecht goes on to explain.
The production of iron using sustainably generated ‘green’ hydrogen is considered technologically promising. In this process, hydrogen replaces carbon-containing coke. Consequently, almost no CO₂ emissions are produced during iron production. Another alternative is still in its early stages of development: the electrolysis of the raw material iron ore directly using electricity, also known as ‘electrowinning’. It has the advantage that the electricity is used directly. This is because if electricity is first used to produce hydrogen via water electrolysis, energy efficiency is lower and the carbon footprint of iron and steel production is therefore potentially higher.

Scenarios show: climate targets pose major challenges for the steel industry

In 2020, the global steel industry was already producing around 1,600 million tonnes of crude steel annually. By 2060, global steel production could grow to over 2,600 million tonnes per year. Given this trend, global annual greenhouse gas emissions can, at best, only be reduced by up to 67 per cent by 2060 (from 3.4 gigatonnes of CO₂ equivalents per year in 2020 to 1.2 gigatonnes in 2060). Residual emissions stem primarily from CCS technologies, which prevail in the cost-optimising scenario but whose long-term emission reduction potential is insufficient. ##“This means that no scenario achieves the target – that is, remaining within the CO₂ emissions budget set in this study for the global steel industry in order to limit the temperature rise to 1.5 degrees Celsius,” explains DLR expert Carina Harpprecht. “The steel industry, too, illustrates just how crucial the next ten years will be for climate protection – and how little time remains to further develop and implement new technologies. The high levels of investment in the steel industry and the long remaining service life of existing blast furnaces, potentially combined with CCS, pose major challenges.”
If primary steel production were switched to sustainably produced hydrogen, the cumulative greenhouse gas emissions from the steel industry could be reduced by a further estimated 15 per cent by 2060. However, this would still not be sufficient to meet the CO₂ budget for the 1.5-degree target within this scenario framework. The sector must therefore achieve a faster and more drastic transition away from fossil fuels and a reduction in emissions that goes beyond the levels projected in the global scenarios under consideration. An effective lever for achieving this would be to reduce the production of primary steel whilst placing greater emphasis on steel recycling.

A low-carbon steel industry requires a great deal of renewable electricity

Whether hydrogen or electrowinning – the technological alternatives for reducing emissions in steel production massively increase the demand for electricity from renewable sources: According to a DLR study on the German steel industry, the German steel industry’s electricity demand could be up to fifteen times higher in 2050 than it is today.

DLR: Technology and expertise for steel production using hydrogen

Further research is still needed to replace coke with hydrogen in steel production. The focus is on technologies for so-called direct reduction. In this complex chemical process – to put it very simply – hydrogen reacts with iron oxide to form water vapour and iron, the starting material for steel. The direct reduction process is also possible using natural gas and is already being tested on an industrial scale. The challenge in producing ‘green’ steel and significantly reducing CO₂ emissions lies in replacing natural gas with hydrogen from renewable sources. However, green hydrogen will remain more expensive than fossil-based alternatives for the foreseeable future. That is why the DLR Institute for Low-Carbon Industrial Processes is working to optimise the design and efficient operation of processes and plants. To this end, the DLR is currently setting up a laboratory-scale demonstration reactor and developing numerical models. This work is vital for overcoming several challenges: hydrogen from renewable but highly variable sources such as wind or solar energy will not initially be as reliably available as fossil natural gas. In addition, researchers at the DLR are also investigating renewable carbon sources and the use of low-grade iron ores in steel production.
Source: DLR