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Synergistic gas–slag scheme to mitigate CO2 emissions from the steel industry

Nature Sustainability volume 8, pages 763–772 (2025)Cite this article

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Abstract

Improving the sustainability of the steel industry requires decarbonization strategies that are both technically and economically viable. The recovery of both material and heat on site is a promising approach but largely unexplored. Here we propose a scheme integrating heat recovery, carbon mineralization and the use of slag in cement production, along with the blast-furnace injection of hydrogen from off-gas. The proposed scheme, based on the synergistic use of coke oven gas and slag, can reduce CO2 emissions by 48% compared to the conventional approach. When coupled with an external gas supply from coal gasification or biomass pyrolysis, CO2 emissions can drop by 63% and 92%, respectively. The cost of avoiding CO2 emissions could be less than half the cost of conventional industrial capture and could be offset by the projected carbon price by 2030. For the steel industry in China, we find that the scheme is applicable to over 46% of existing steel mills, resulting in 16 provinces meeting the 2 °C target and 19 provinces surpassing the 50% national mitigation target. Overall, we have shown how a minor reconfiguration of the steel production process could substantially improve the sustainability of the steel industry.

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Fig. 1: Concept and scenarios of the synergistic gas–slag decarbonization scheme.
Fig. 2: Performance of the synergistic gas–slag decarbonization scheme with slag feed ratios ranging from 0% to 100% for production of 1 t of pig iron.
Fig. 3: Decarbonization potential and economic competitiveness of the proposed scheme.
Fig. 4: Technology promotion potential and decarbonization contribution to China’s steel industry under the proposed scenarios.
Fig. 5: Impact of the three proposed scenarios on air quality and the reuse benefits of solid waste.

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Data availability

All data and parameters used for this study are provided in the Supplementary Information.

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Acknowledgements

This work was financially supported by the National Nature Science Foundation of China (grant no. U21A20321 to F.C. and grant no. 72025401 to X.L.). We thank the National Key Research and Development Program of China (grant no. 2024YFC3909301 to Z.D. and F.C.), the Carbon Neutrality and Energy System Transformation Program (X.L.) and the Research Project Supported by Shanxi Scholarship Council of China (grant no. 2022-018 to Z.D.) for their support.

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Authors and Affiliations

  1. Institute of Resources and Environmental Engineering, Shanxi University, Taiyuan, China

    Zichen Di, Yanxia Wang, Chenggong Chang, Huiping Song & Fangqin Cheng

  2. Yellow River Laboratory of Shanxi Province, Taiyuan, China

    Zichen Di, Huiping Song & Fangqin Cheng

  3. School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, China

    Zichen Di & Xi Lu

  4. Institute for Carbon Neutrality, Tsinghua University, Beijing, China

    Xi Lu

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  1. Zichen Di
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Contributions

Z.D., X.L. and F.C. designed the research. Z.D., Y.W., C.C. and H.S. performed the comprehensive model simulation and data compiling processes. F.C. gave important guidance on the scenario selection and analyses. Z.D. and X.L. wrote the article. All authors contributed to the discussions and paper revision.

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Correspondence to Xi Lu or Fangqin Cheng.

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Nature Sustainability thanks Lei Zhu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Notes 1–8, Figs. 1–9 and Tables 1–27.

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Di, Z., Wang, Y., Chang, C. et al. Synergistic gas–slag scheme to mitigate CO2 emissions from the steel industry. Nat Sustain 8, 763–772 (2025). https://doi.org/10.1038/s41893-025-01572-2

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