Product

Bauxite residue is the insoluble solid waste generated during the processing of bauxite into alumina via the Bayer Process. It is separated from the pregnant sodium aluminate liquor during the clarification stage and represents the fraction of bauxite that cannot be dissolved in caustic soda.​

Figure 1 — The Bayer process

Composition

Red mud is a heterogeneous mixture of oxide compounds and residual minerals from the parent bauxite that were not solubilised during digestion:

Key Physical & Chemical Characteristics

Generation Rate

For every tonne of alumina produced, approximately 1.0–1.5 tonnes of red mud are generated, with a global average of 1.23 tonnes. Given that global alumina production exceeds 130 million tonnes per year, red mud generation represents one of the largest industrial waste streams in the world.

Environmental Concerns

Red mud's high alkalinity (pH 10–13) and content of trace heavy metals make it a significant environmental hazard:

• Long-term storage in large tailings ponds risks alkaline leachate contamination of soil and groundwater
• Pond failures can cause catastrophic spills — the most notable being the Ajka disaster in Hungary (2010), when a dam breach released approximately 1 million m³ of red mud
• The US EPA classifies bauxite refinery residuals as TENORM (Technologically Enhanced Naturally Occurring Radioactive Material) due to concentration of naturally occurring radioactive elements during refining​

Valorisation & Reuse

Significant research effort is directed at converting red mud from a waste into a resource:​

• Iron and steel production — recovery of iron from the iron oxide fraction
• Rare earth element recovery — red mud contains elevated concentrations of scandium and other REEs
• Cement and construction materials — as a supplementary cementitious material or in road base applications
• Geopolymers — as an alkali-activated binder material
• Soil amendment — neutralised red mud used to remediate acid sulfate soils

References

1. Wikipedia. Red mud (Page version Feb 23, 2026)
2. Everything.Explained.Today. Red mud explained (Accessed Feb 26, 2026)
3. RedMud.org. Red Mud Project (Accessed Feb 26, 2026)
4. Bian J, Li S, Zhang Q. (Sep 21, 2022). Experimental Investigation on Red Mud from the Bayer Process for Cemented Paste Backfill. Int J Environ Res Public Health. 19(19):11926. DOI: 10.3390/ijerph191911926. PMID: 36231225; PMCID: PMC9565261
5. Patel, S., & Pal, B.K. (Aug 2015). Current status of an industrial waste: Red mud an overview. IJLTEMAS, 4(8), 1-16
6. FluidFlow. The Bayer Process: Fluid Flow in Alumina Plants (Mar 15, 2022)
7. U.S. Environmental Protection Agency (EPA). TENORM: Bauxite and Alumina Production Wastes (Apr 22, 2015)
8.  Industry-University Cooperative Research Centers Program (IUCRC), The National Science Foundation (NSF). Catalyzing Commercialization: An Economically Viable Process to Recover High-Value Products from Red Mud (Jun 17, 2020)