Bauxite Residue / Red Mud

Bauxite residue, better known as red mud, is the alkaline waste left behind when alumina refineries process bauxite. It carries the rare earths and scandium that the refining process leaves behind, and refineries produce it in huge volumes. That makes red mud rare earths mostly a scandium question. Scandium comes only as a byproduct, and the USGS counts previously processed residues among the metal's sources.

What red mud is

Red mud is the solid residue of the Bayer process, and refineries generate about 0.7 to 2 tons of it for every ton of alumina (Reid et al., Scientific Reports, 2017). The same paper cited annual global production of about 140 million tons. Residue volume tracks alumina output, which was an estimated 150 million metric tons in 2025 (USGS Mineral Commodity Summaries 2026).

The residue is highly alkaline, with a pH of 10 to 12.5 (Alkan et al., Scientific Reports, 2018). It is a caustic mix of silicon, iron, aluminum, calcium, titanium and sodium oxides. In 2022, Efthymios Balomenos of Mytilineos, the Greek alumina producer now named Metlen, said only 3% of it is reused as a raw material (CORDIS).

Red mud rare earths and where they sit

The rare earths in bauxite end up in the residue at about twice their original concentration, because they sit in iron and titanium minerals that the Bayer process leaves unchanged (Reid et al.). One sample in that 2017 study held about 0.03 weight percent rare earths, mainly cerium, lanthanum, neodymium, scandium and samarium.

Content depends on the bauxite. A 2017 USGS report notes that Jamaican red mud reportedly contains 0.23 to 0.38 weight percent rare earths, citing a 1987 study (USGS Professional Paper 1802-O).

Cerium tends to sit with titanium, while scandium is tied to iron and aluminum compounds (Reid et al.). In the Greek bauxite and residue samples a 2018 study analyzed, scandium was mainly hosted in hematite, where it probably takes the place of iron in the crystal (Vind et al., Minerals Engineering, 2018).

Why red mud matters for scandium supply

In 2025, scandium was produced only as a byproduct, mainly from nickel and titanium process streams and from previously processed tailings and residues. Global production was about 80 metric tons of scandium oxide equivalent, and China was the leading producer (USGS MCS 2026).

Reid and coauthors note that material with 20 to 50 ppm scandium can be considered ore, and call bauxite residue a suitable source (Scientific Reports). A bulk sample of Greek residue held 98 mg/kg (Vind et al.).

Why recovery from red mud is hard

Direct acid leaching is the most studied route, and a 2018 study names two drawbacks. Dissolved silica forms a gel, and leaching has low selectivity. In the Greek residue that study used, which is about 40% iron oxide, iron dissolves along with the scandium and titanium and complicates their recovery (Alkan et al.). In the 2017 study, concentrated nitric acid leached best, but the authors chose sulfuric acid because of process complexities, including the difficulty of removing nitrate from the leftover residue (Reid et al.).

Scandium projects using red mud (as of October 2026)

Rusal, Russia. In August 2016, Rusal said a pilot unit at its Urals smelter (UAZ) had produced its first scandium oxide from red mud (Rusal). In February 2025, Rusal said it was setting up a pilot production facility for scandium oxide with capacity of 1.5 metric tons a year at its Bogoslovsky smelter in Krasnoturyinsk. The facility was scheduled to be commissioned by the end of 2025 (Rusal). REEx found no Rusal announcement that the facility had been commissioned.

ElementUSA, Louisiana. In November 2025, the Department of War awarded ElementUS Minerals, LLC (ElementUSA) $29.9 million to develop a demonstration facility in Gramercy to separate and purify gallium and scandium from existing industrial waste (Department of War). ElementUSA holds exclusive rights to the bauxite residue at the Atalco alumina refinery in Gramercy (Colorado School of Mines). As of December 2025, construction of the demonstration facility was expected to begin in mid-2027, with initial production targeted for the third quarter of 2028 (Louisiana Economic Development).

In June 2026, the Department of Energy selected a Colorado School of Mines project with ElementUSA for award negotiations, for a plant that would extract rare earths from the Gramercy red mud (DOE). DOE said selection is not a commitment to issue an award, and Mines put the funding at $67 million, with lanthanum among the target elements (Colorado School of Mines). REEx described ElementUSA that month as a private, development-stage company still facing commercial-scale execution (REEx coverage).

European pilots, Greece. The EU-funded SCALE project, coordinated by Mytilineos from 2016 to 2021, produced scandium concentrates at pilot scale from 10 metric tons of bauxite residue, along with acid waste from titanium dioxide production (CORDIS). In September 2021, Mytilineos said the SCALE scandium pilot plant had started operating a year earlier at its Aluminium of Greece plant (Mytilineos).

The RemovAL project, run from 2018 to 2023, smelted bauxite residue with other industrial byproducts. The slag went into hydrometallurgical pilots in Greece and Germany to recover aluminum and titanium oxides plus scandium and gallium (CORDIS). Another EU project, EURARE, investigated extracting scandium and rare earths from Greek bauxite residue (REEx coverage).

In July 2026, REEx noted that Enervoxa, which proposes a red mud rare earth plant in India, had not publicly disclosed demonstration-plant performance or verified recovery rates (REEx coverage).

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