Uneven renewable energy supply constrains the decarbonization effects of excessively deployed hydrogen-based DRI technology.

Hydrogen-based direct reduced iron (H-DRI) is crucial for decarbonizing the steel sector but is limited by the availability of renewable energy. Here, we propose H-DRI deployment schemes in China's steel sector at moderate and aggressive scales, incorporating three renewable energy sources with a resolution of 1 km × 1 km across 570 steel units. Results indicate that 52.6-55.8% of China's current steel units lack sufficient renewable energy supply for H-DRI deployment due to uneven distribution of these energy sources. Renewable energy can fulfill 97-100% of hydrogen demand at the moderate scale, whereas the aggressive scale requires supplemented fossil fuels accounting for one-third to one-half. H-DRI can decarbonize steel production to 0.15-0.91 t CO t steel at the moderate scale, but the emissions would raise by up to over sixfold at the aggressive scale. Furthermore, H-DRI fueled by solar and wind energy exhibits poorer economic and water usage performance at the aggressive scale. We highlight the necessity of avoiding excessive H-DRI deployment and recommend prioritizing its implementation in steel units located in regions with abundant solar and wind sources nearby.