Revealing cradle-to-gate CO2 emissions for steel product producing by different technological pathways based on material flow analysis

Revealing the life-cycle CO2 emissions of steel products is of great significance for mitigating CO2 emissions. However, previous studies did not conduct comparative analysis for steel products produced by different technological pathways, resulting in considerable confusion in the setting of carbon reduction pathways. By using the material flow analysis method, this study revealed the life-cycle CO2 emissions associated with various technological pathways. The results shows that life-cycle CO2 emissions per metric ton of steel are: 3620.78 kg for shaft furnace (SF)-electric furnace (EF) routes, 2598.54 kg for blast furnace (BF)- basic oxygen furnace (BOF), 1868.16 kg for Scrap & Molten Iron-EF and 1330.22 kg for scrap-EF. The energy structure (e.g. coal blending mode, power generation mode) material structure (e.g. iron ore matching mode, matching mode of scrap and molten iron), and transportation mode have a significant impact on CO2 emissions. Undoubtedly, low-carbon or zero-carbon electricity is more effective in reducing CO2 emissions.