CO₂ mitigation via accelerated limestone weathering

We evaluate accelerated weathering of limestone (AWL: CO₂ + CaCO₃ + H₂O=> Ca²⁺ + 2HCO₃^-) as a low-tech, inexpensive, high-capacity, environmentally-friendly CO₂ capture and sequestration technology. With access to seawater and limestone being essential to this approach, significant limestone resources are close to most CO₂-emitting power plants along the coastal US. Waste fines, representing more than 20% of current US crushed limestone production (>10⁹ tonnes/yr), could be used as an inexpensive source of AWL carbonate. Under such circumstances CO₂ mitigation cost could be as low as $3-$4/tonne. More broadly, 10-20% of US point-source CO₂ emissions could be treated at $20-$30/tonne CO₂. AWL end-solution disposal in the ocean would significantly reduce effects on ocean pH and carbonate chemistry relative to those caused by direct atmospheric or ocean CO₂ disposal. Indeed, the increase in ocean Ca²⁺ and bicarbonate offered by AWL should enhance growth of corals and other calcifying marine organisms.