Abstract

Despite basalt-based Enhanced Rock Weathering (ERW) showing promise in croplands, identifying alternative application sites is crucial for scaling carbon dioxide removal (CDR) and maximizing co-benefits. This study investigated acid mine drainage (AMD) systems as potential ERW sites, emphasizing the use of mining waste rock as reactive material. AMD environments are naturally acidic and characterized by continuous flow, conditions that accelerate mineral dissolution and enhance ERW effectiveness. Field-scale ERW trials were conducted in two AMD-impacted rivers in Japan using locally sourced basaltic waste rock (1–2 mm). At each site, one ton of crushed rock was deployed: (1) Yoshioka basaltic andesite (Yk) in the Amemasu River, and (2) Tetsuzan basalt (Tz) in the Shojin River. After one year, ∼0.79 tons of Yk and ∼0.36 tons of Tz remained, reflecting substantial dissolution. Rapid weathering of volcanic glass in matrix phases caused particle fragmentation and increased reactive surface area, while the absence of alteration rinds confirmed congruent dissolution. Hydrochemical monitoring revealed sustained Ca²⁺ and Mg²⁺ release, pH elevation, and schwertmannite precipitation. Schwertmannite co-precipitated arsenic without passivating rock surfaces, while proton release during its formation partly preserved acidic conditions that favor continued dissolution. These results highlight AMD systems as strategic ERW sites, offering a dual cleaner-production pathway: (i) rapid and sustained weathering ensures CDR potential, and (ii) passive treatment of contaminated mine waters provides remediation benefits. Leveraging mining by-products for ERW not only reduces the environmental burden of rock extraction but also creates opportunities for integrated waste valorization, climate mitigation, and sustainable mine-site management.

Credit: Hkaung et al., Cleaner Engineering and Technology, 32, 101203 (2026), https://doi.org/10.1016/j.clet.2026.101203. Licensed under CC BY 4.0.