From article: " Important examples are hydrogen-based direction reduction (HyDR),[4] hydrogen plasma smelting reduction,[5] and various electrolysis processes

From article: " Important examples are hydrogen-based direction reduction (HyDR),[4] hydrogen plasma smelting reduction,[5] and various electrolysis processes (e.g., molten oxides’ electrolysis,[6] molten salt electrolysis,[7] waster-assisted molten salt electrochemical reduction,[8] and electrowinning of solid iron from aqueous solutions[9]). Among these alternatives, the HyDR approach has today reached the highest technology readiness level (TRL 6–8) and is currently being deployed at industrial scale.[2, 10] In this process, green hydrogen should be ideally used, i.e., hydrogen that has been produced using renewable energy sources, generating water instead of carbon dioxide as redox product.[4] " This article is trying to make HyDR more green since it's already deployed more at an industrial level compared to alternatives at the moment.