PubMed · 2026-06-30
Adding crushed volcanic rock to soil, a technique called enhanced weathering, doesn't reliably trap carbon dioxide, and mixing it with manure may actually slow the rock's breakdown. A 389-day experiment paired with geochemical modeling found that carbon ended up locked in clay minerals rather than removed from the atmosphere, and that organic amendments reduced basalt's reactive surface area.
Over 389 days, silicate rock amendments (basalt and dunite) produced no significant increase in dissolved or solid carbon storage compared to unamended controls.
Adding organic matter (manure) reduced basalt's reactive surface area and decreased leached potassium and iron, directly counteracting rock weathering rates.
Geochemical modeling confirmed that released base cations preferentially form secondary clay minerals rather than carbonates, limiting net CO2 removal from the atmosphere.