This landscape tracks 204 published records filed between 2015 and the 2026 data cut-off, built around a search covering neutralisation potential, oxygen barriers, passive treatment, seepage collection, sulfide oxidation rate and microbial oxidation. The true figure for very recent years understates activity because publication typically lags filing by around 18 months. Anyone using this number for a freedom-to-operate assessment should treat 2025 and 2026 figures as provisional and expect them to rise.

Filing is led by a single assignee with 21 records, but ownership is not tightly concentrated: the top 5 assignees combined hold only 32.4% of the 204 records in scope, and the top 10 hold 50.0%. The remaining half of the field is spread across a long tail drawn from an 88-company ranking, including mining-technology firms, national geoscience institutes and university research groups. This spread means no single player controls the core prevention mechanisms outright.

Filings peaked at 20 in 2020 and have since declined, with the last fully comparable window showing a fall from 5 filings in 2021 to 1 in 2024, an -80% change. That said, publication lag means 2025 and 2026 counts are still filling in and should not be read as confirmation of a permanently shrinking field. The honest reading is that visible activity has thinned through the most recent complete year, not that the technology area is closed.