173 / 2024-09-10 16:22:31

Potential of CO2 Sequestration through Accelerated Weathering of Limestone on Ships

marine carbon dioxide removal,carbon sequestration

Session 33 - Ocean Negative Carbon Emissions

Benthic dissolution of CaCO₃ is the dominant negative feedback in the ocean for the neutralization of acidity due to rising atmospheric CO₂. Mimicking this natural process, the accelerated weathering of limestone (AWL) can store carbon as bicarbonate ions in the ocean for tens of thousands of years (Rau and Caldeira 1999). Here, we evaluate the potential of AWL on ships as a carbon sequestration approach and a pathway to significant decarbonization of maritime transportation. Data from small scale reactors in the lab are successfully predicted by a model that includes the most recent kinetics for calcite dissolution in seawater. This model is then applied to ship-scale reactors to examine the ability of AWL to efficiently store carbon from the shipping industry in the ocean while a vessel is underway. When our reactors are simulated along a Pacific shipping lane in the ECCO-Darwin ocean-GCM model, the alkalinity and dissolved inorganic carbon (DIC) increase by less than 30 μmol·kg^-1 at the sea surface after 10 years of continuous operation, with less than 2.5% changes in air-sea CO₂ fluxes. Pre-reacting CO₂ with limestone results in an effluent pH of > 6.3 as it leaves a ship thus meeting all current IMO regulations for acidic ship stack scrubbers.