Combining Multi-Satellite Products for Monitoring the Steel Industry: A Case Study of ArcelorMittal Asturias Facilities

Accurate monitoring of iron and steel factories is crucial for both economic efficiency and environmental protection. Steel plays a key role in the European (EU) economy, including its green transition, due to its use across numerous strategically important sectors. The EU steelmaking industry is the world’s third largest producer, with sites distributed across more than 20 Member States. Steel plants sustain many regional economies, emphasizing their socio-economic and political significance. Industrial complexes are major heat sources composed of multiple small-scale operating assets, which can be effectively analyzed using heterogenous infrared satellite indicators at medium to high spatial resolution. In this study, for the first time, a multi-source approach integrating two thermal anomaly indices, the Thermal Anomaly Index (TAI) and the Normalized Hotspot Index (NHI), derived from 20m infrared satellite imagery, is proposed. The ArcelorMittal facilities in Asturias, Spain (Avilés and Gijón), operated by the world’s second largest steel producer, were selected to calibrate and validate the methodological framework. Preliminary results show a strong correlation (R2 ≈ 0.7₋1.00) between detected activations (used as proxies for production rates) and ground-truth data (annual crude steel and pig iron production) for 2016˗2024, across multiple spatial scales (from national to individual assets). Application to steelmaking facilities in France and Germany further confirms the robustness of the approach. Independent data on steel production are essential to better assess the environmental impacts of the sector, as production levels are directly linked to emissions and pollution. The satellite-based methodology presented here provides an objective means to quantify steel output where official data are incomplete or unavailable, enabling consistent assessments of national exposure to steelmaking activities and progress toward decarbonization.