The steel industry is recognized as one of the most challenging sectors to decarbonize. This movie explores reasons for this difficulty, including the fundamental reliance on carbon-based processes, technological and economic constraints, and the sector's global economic significance.
The primary challenge in reducing CO2 emissions from the steel sector lies in the industry's dependence on carbon-intensive processes, particularly the blast furnace-basic oxygen furnace (BF-BOF) route. This traditional method, responsible for approximately 70% of global steel production, relies on coke (a carbon-rich material derived from coal) as a reducing agent to convert iron ore into iron. The chemical reactions involved in this process inherently produce CO2.
As long as coke remains the primary reducing agent, significant CO2 emissions are unavoidable.
2. Technological Constraints
While alternative methods, such as direct reduced iron (DRI) and electric arc furnace (EAF) technologies, offer lower carbon footprints, they face substantial limitations. DRI, for example, can use natural gas or hydrogen as reducing agents, which substantially reduces CO2 emissions. However, this technology is not universally applicable due to regional variations in the availability and cost of natural gas and hydrogen. Additionally, transitioning to hydrogen-based DRI requires substantial investment in new infrastructure and the development of a green hydrogen supply chain, which is currently limited.
Electric arc furnaces, which use scrap steel as a primary input and rely on electricity, can also reduce emissions significantly if the electricity comes from renewable sources. However, the availability of scrap steel is finite, and the quality of recycled steel can be inferior to that produced from iron ore, limiting its application in certain high-grade steel products.
3. Economic Considerations
Decarbonizing the steel industry is capital-intensive. Retrofitting existing plants or building new ones to accommodate low-carbon technologies involves substantial financial investments. For instance, the development of hydrogen-based steel production requires new technologies, storage facilities, and distribution networks for hydrogen, all of which represent significant economic barriers.
Moreover, the steel industry operates in a highly competitive global market. The increased costs associated with adopting low-carbon technologies can lead to higher steel prices, potentially reducing the competitiveness of companies that invest in these technologies. This economic reality often leads to a "wait-and-see" approach, where firms delay significant investments in decarbonization until there is greater certainty about regulatory frameworks and market conditions.
4. Scale and Inertia of Existing Infrastructure
The steel industry is characterized by large-scale, long-lived infrastructure. The typical lifespan of a blast furnace is around 20-40 years, and replacing or retrofitting such facilities to adopt new technologies cannot be done rapidly. The sheer scale of the industry means that transitioning to new technologies involves not just technological shifts but also logistical and operational challenges on a massive scale.
6. Material and Energy Efficiency Improvements
While improvements in material and energy efficiency have been made, these measures alone are insufficient to achieve the deep decarbonization needed. Technologies such as Carbon Capture and Storage (CCS) offer potential pathways to mitigate emissions from existing plants, but these technologies are still in the development stage and face economic and practical challenges in scaling up.
7. References and Further Reading
1. Raabe, D., Tasan, C. C. & Olivetti, E. A. Strategies for improving the sustainability of structural metals. Nature 575, 64-74 (2019).
2. Raabe, D. The Materials Science behind Sustainable Metals and Alloys. Chem. Rev. 123, 2436-2608 (2023).
3. Kim, S. H. et al. Influence of microstructure and atomic-scale chemistry on the direct reduction of iron ore with hydrogen at 700°C. Acta Mater. 212, 116933 (2021).
4. Souza Filho, I. R. et al. Green steel at its crossroads: Hybrid hydrogen-based reduction of iron ores. J. Clean. Prod. 340, 130805 (2022).
5. Ma, Y. et al. Hierarchical nature of hydrogen-based direct reduction of iron oxides. Scr. Mater. 114571 (2022).
6. Ma, Y. et al. Hydrogen-based direct reduction of iron oxide at 700°C: Heterogeneity at pellet and microstructure scales. Int. J. Miner. Metall. Mater. 29, 1901-1907 (2022).
7. Bai, Y. et al. Chemo-Mechanical Phase-Field Modeling of Iron Oxide Reduction with Hydrogen. Acta Mater. 231, 117899 (2021).
8. Ma, Y. et al. Reducing Iron Oxide with Ammonia: A Sustainable Path to Green Steel. Adv. Sci. 2300111, 1-7 (2023).
9. Jovičević-Klug M, Souza Filho IR, Springer H, Adam C, Raabe D. 2024. Green steel from red mud through climate-neutral hydrogen plasma reduction. Nature. 625(7996):703-9