Red mud

Red mud, now more frequently termed bauxite residue, is an industrial waste generated during the processing of bauxite into alumina using the Bayer process. It is composed of various oxide compounds, including the iron oxides which give its red colour. Over 97% of the alumina produced globally is through the Bayer process; for every tonne (2,200 lb) of alumina produced, approximately 1 to 1.5 tonnes (2,200 to 3,300 lb) of red mud are also produced; the global average is 1.23. Annual production of alumina in 2023 was over 142 million tonnes (310 billion pounds) resulting in the generation of approximately 170 million tonnes (370 billion pounds) of red mud. Due to this high level of production and the material's high alkalinity, if not stored properly, it can pose a significant environmental hazard. As a result, significant effort is being invested in finding better methods for safe storage and dealing with it such as waste valorization in order to create useful materials for cement and concrete. Less commonly, this material is also known as bauxite tailings, red sludge, or alumina refinery residues. Increasingly, the name processed bauxite is being adopted, especially when used in cement applications.