Maximizing Carbonate Weathering Rates in an Open-System Benchtop Reactor as a Means of CO₂ Capture

Capping global warming at under 1.5 °C requires reducing the CO₂ concentration in the atmosphere. This study investigates the capture of CO₂ from power plants by enhancing carbonate weathering using an open-system benchtop reactor. The reactor, filled with natural carbonate rocks, was continuously flushed with seawater and CO₂ gas. In 14 experiments, we tested the effects of CO₂ flow rates, gas recycling, grain size, mineralogy, and postexperiment equilibration with the atmosphere. Moderate gas recycling improved weathering efficiency, while excessive recycling reduced the efficiency. Smaller grains resulted in a higher total weathering amount, while larger grains resulted in higher weathering rates. A CO₂ gas-to-seawater flux ratio of 10-20 was found to be most efficient for enhanced weathering. Only 20% of introduced CO₂ was successfully utilized for carbonate weathering, indicating that efficiency improvements are needed. In calcite weathering experiments, dilution with seawater postexperiment prevented carbonate reprecipitation. Dolomite weathering rates stabilized at similar values to calcite, and its products did not reprecipitate carbonate, indicating that dolomite may be preferred for more efficient carbon sequestration. These results highlight the feasibility of enhancing carbonate weathering in an open-system reactor and offer practical strategies to sequester carbon from power plants.