Filing in this dataset is concentrated: the leading assignee holds 29 of the 271 records in scope, more than three times the count at fifth place (9 records). Below the top ten filers, activity spreads across a long tail of roughly 100 ranked companies, most with only one or two families. This shape means a freedom-to-operate check should weight the leader's portfolio heavily rather than treat the field as evenly distributed.

Filings peaked at 24 in 2022 and had fallen to 10 by 2024, a 47% decline from the 19 filings recorded in 2021. Because patent publication typically lags the filing date by around 18 months, the 2025 and 2026 figures in any trend chart are still incomplete and should not be read as continued decline. The honest read is a pullback from a 2022 peak, with the most recent one to two years too thin to interpret yet.

Metal extraction and refining (IPC class C22B) appears in 52.4% of the 271 records in scope, the single largest technology grouping, followed by alkaline-earth and aluminium compound chemistry (C01F) at 34.3%. Ceramics and refractory reuse, separation techniques, iron production and water treatment each appear in under 20% of records. That gap indicates extraction and recovery chemistry is the most heavily claimed area, while reuse and treatment applications remain comparatively open.

US5607598A describes a multi-stage centrifuge and repulp washing process that produces a caustic-lean, alumina-lean red mud cake, then reslurries that cake with bauxite sand for disposal in a dry stacking impoundment. Anyone implementing sequential centrifuge washing followed by sand-blended dry stacking should review this filing's specific claim scope before designing a process around that combination. It does not obviously reach single-stage dewatering, non-centrifuge separation methods, or reuse pathways that avoid impoundment disposal entirely, which is where alternative approaches typically sit.

Based on the IPC composition, surface revegetation, residue storage geotechnical design, and integration of water treatment with leachate management all sit at meaningfully lower filing density than the extraction-chemistry core of C22B and C01F. Magnetic and electrostatic separation of iron fractions (B03C, 12.2% of records) and ceramic reuse of treated residue (C04B, 18.8%) are also less crowded than the core recovery chemistry. These branches are worth checking first for a new filing, since claim space there is less occupied — though lower density is not proof the technology is easy to practise, only that fewer claims currently sit on it.