With the help of scenarios, the DLR has analysed how greenhouse gas emissions from global iron and steel production can be reduced. The researchers analysed the capture and storage of CO2 (CCS), the use of hydrogen and the electricity-based production of iron. The results show that the reduction in emissions enabled by CCS for coal-based plants is insufficient for meeting long-term climate targets. By contrast, hydrogen-based and electrified technologies using green electricity are the key technologies.
In a study, the German Aerospace Centre (DLR) has investigated how the global steel industry can significantly reduce its CO2 emissions. This is an important starting point in the fight against global warming, since iron and steel production is responsible for around nine per cent of global greenhouse gas emissions. In their study, the researchers from the DLR Institute of Networked Energy Systems used several scenarios to analyse how the introduction of new technologies could affect greenhouse gas emissions from global iron and steel production. Three technologies are at the focus: carbon capture and storage (CCS), the use of hydrogen, and the electricity-based production of iron. ##“The study demonstrates that comprehensive and far-reaching measures – flanked by a political framework at international level – are necessary in the near future. This is the only way to sufficiently drive forward defossilisation of the steel industry and, at the same time, ensure competitiveness in Germany and Europe. Another fundamental prerequisite is the rapid and massive expansion of electricity generation from renewable sources,” summarises Prof. Meike Jipp, DLR Divisional Board Director for Energy and Transport. “This is also in light of the fact that, due to EU emissions trading, the cost of CO2 emissions will gradually increase in the future, making existing production processes more expensive. It is therefore imperative to incentivise and implement new technologies now.”
Capturing and storing CO2 is not enough
Steel is produced in blast furnaces. The main energy source used is coke, a special type of coal. The CO2 emissions from steel production are correspondingly high: between 1.6 and 2.2 tonnes of CO2 are produced per tonne of steel. If existing blast furnaces are retrofitted with technologies that capture and store CO2, CO2 emissions can be significantly reduced. “Our analysis reveals that these technologies can reduce emissions in the short term, because CCS enables modern existing plants to be retrofitted. In the long term, however, the emission reduction potential of CCS is insufficient,” summarises DLR researcher Carina Harpprecht. She produced the DLR study together with colleagues from the Energy Systems Analysis department. “Electrification of the production process is the key strategy for achieving a far-reaching reduction in emissions,” Harpprecht continues. Production of iron using sustainably produced “green” hydrogen is considered technologically promising. The hydrogen replaces the carbon-containing coke. As a result, almost no CO2 emissions are generated during iron production. Another alternative is not yet fully developed: electrolysis of the raw material iron ore under the direct use of electricity, also known as “electrowinning”. The direct use of electricity is its benefit because otherwise, if electricity is used to first produce hydrogen by means of water electrolysis, energy efficiency is lower and so the carbon footprint of iron and steel production is potentially higher.
Scenarios demonstrate that 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 per year. By 2060, global steel production could grow to over 2,600 million tonnes per year. In view of this development, global annual greenhouse gas emissions can only be reduced by up to 67 per cent by 2060 in the best-case scenario (from 3.4 gigatonnes of CO2 equivalents per year in 2020 to 1.2 gigatonnes in 2060). Residual emissions come primarily from CCS technologies, which prevail in the cost-optimising scenario. Their potential for long-term emission reduction is, however, insufficient. “This means that no scenario leads to the goal – i.e. staying below the CO2 emissions budget set for the global steel industry in this study in order to limit the temperature rise to 1.5 degrees Celsius,” explains DLR expert Carina Harpprecht. “In the steel industry, too, it is clear how important the next ten years will be for climate protection – and how little time remains to further develop and implement new technologies. The high investment sums in the steel industry and the still long service life of existing blast furnaces, potentially combined with CCS, pose major challenges.”
If the primary production of steel were to be converted to sustainably produced hydrogen, it is estimated that the steel industry’s cumulative greenhouse gas emissions could be reduced by a further 15 per cent by 2060. However, this would still not be sufficient to meet the CO2 budget for the 1.5 degree target in this scenario framework. The sector must therefore achieve faster and more drastic defossilisation and emission reductions that go beyond the values projected in the global scenarios under consideration. An efficient lever for this would be to reduce the production of primary steel and at the same time focus more on the recycling of steel.
Low-CO2 steel industry requires a lot of renewable electricity
Whether hydrogen or electrowinning – the technological alternatives for lower emissions in steel production are massively increasing the demand for electricity from renewable sources: it is estimated that the German steel industry’s electricity requirements could be up to fifteen times higher in 2050 than they are today, according to a DLR study on the German steel industry.
DLR: Technology and expertise for steel production using hydrogen
Further research is needed to replace coke with hydrogen in steel production. The focus is on technologies for so-called direct reduction. To simplify roughly, in this complex chemical process hydrogen reacts with iron oxide to form water vapour and iron, the raw material for steel. The direct reduction process is also possible with natural gas and is already being trialled on an industrial scale. For “green” steel and significantly lower CO2 emissions, the challenge is to replace natural gas with hydrogen from renewable sources. However, green hydrogen will remain more expensive than fossil alternatives for the foreseeable future. That is why the DLR Institute of Low-Carbon Industrial Processes is working on optimising the design and efficient operation of processes and plants. DLR is currently building a laboratory-scale demonstration reactor and developing numerical models. This work is important in order to overcome several challenges: that is because hydrogen from renewable but highly fluctuating resources such as wind or solar energy will initially not be as reliably available as fossil natural gas. DLR researchers are also investigating renewable carbon sources and the use of low-grade iron ore in steel production.
Source: DLR
