A Cornell-led study suggests spreading crushed basalt on farmland may remove far less carbon dioxide from the atmosphere than widely cited estimates predict.
The research, published Aug. 26 in Nature, examined natural volcanic landscapes and found chemical reactions and limited water movement can prevent much of the alkalinity produced by weathering from reaching rivers and the ocean.
That matters because long-term carbon storage depends on the alkalinity moving out of soil. Many projections count carbon captured when basalt first dissolves without fully accounting for what happens deeper underground.
Researchers found natural basalt watersheds typically export carbon at rates well below projections for agricultural applications. Lead author Louis Derry said the process may offset some emissions but is unlikely to deliver carbon removal on the gigaton scale.
The study does not conclude that enhanced weathering has no benefit, but it calls for more complete measurements before projects claim durable carbon removal.
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