This study explores pyrometallurgical and hydrometallurgical methods for decarbonizing and recovering valuable metals from bauxite residue, with direct hydrogen reduction in a rotary kiln without smelting and dissolution of solid residues under high pressure in an autoclave. The goal is to offer decarbonizing techniques for the removal of iron from bauxite residue, a by-product of the Bayer process, which cannot be disposed of in an environmentally sustainable manner. In contrast to traditional carbon-based reductive melting, which generated significant CO₂ emissions, hydrogen is now being investigated as a cleaner alternative. Through hydrogen reduction in rotary kiln, approximately 99.9% of iron is recovered as iron, which can be separated using magnetic separation from the solid residue containing other valuable metals. We concluded that hydrogen can reduce iron oxide from bauxite residues to metallic iron in contrast to very stable oxides such as titanium oxide, silica and aluminum oxide. Leaching of titanium, iron and aluminum with sulfuric acid has high efficiency under high pressure in an autoclave.