Life-Cycle Environmental Trade-Offs of Steel Slag Treatment Processes: A Comparative Assessment with Process-Level Drivers

Steel slag is a major high-temperature by-product of steelmaking. Stockpiling can cause persistent burdens. Cr(VI) leaching, particulate emissions, and land occupation are key concerns. Many treatment and utilization processes exist. Most studies still assess them one by one. This study compares five representative processes in a consistent life-cycle framework: hot slag splashing (HS), heat recovery (HR), molten slag reconstruction (MSR), mineral carbonation (MC), and cement co-processing (CP). This study applies ReCiPe 2016 and USEtox. This study reports midpoint impacts, endpoint damages, normalization, and sensitivity analysis. The endpoint results show that HS has the largest human-health damage (5.2 × 10−6 DALY·t−1). The endpoint results show that HS also has the largest ecosystem damage (3.4 × 10−6 species·t−1). The endpoint results show that CP and MC have the lowest human-health damages (0.5–0.7 × 10−6 DALY·t−1). The endpoint results show that CP and MC provide net resource credits (−0.9 to −1.2 USD2013·t−1). MSR reduces toxicity through high-temperature immobilization. MSR also increases resource damage (4.5 USD2013·t−1) because the process requires high energy input. MC can achieve net-negative greenhouse-gas results when CO2 fixation exceeds ~80%. CP shows stable benefits through clinker substitution. Sensitivity analysis identifies process-specific parameters as dominant drivers. The results support process selection and process improvement, and the results help limit burden shifting.