Influence of Wave Action on Applications of Olivine-Based Ocean Alkalinity Enhancement on Sandy Beaches

Ocean Alkalinity Enhancement (OAE) is an emerging carbon dioxide removal approach that aims to store additional atmospheric CO₂ as (bi)carbonate in seawater. OAE can be realized through a variety of pathways, one of which is the dispersal of alkaline mineral sand on beaches where wave energy shall accelerate alkalinity formation. Here, we built a “Beach-Machine” to simulate a gradient of wave energy and test its effect on alkalinity formation by olivine, a widely considered mineral for OAE. We find that wave energy strongly (linearly) increases alkalinity formation from olivine when energy input is beyond a certain threshold. However, when olivine is mixed with organic-poor sand, energy input also increases the loss of alkalinity possibly by promoting precipitation reactions thereby canceling out the benefits of waves on alkalinity formation. Our experiments show that the effects of wave energy on OAE efficiency are dependent on the sediment where olivine-based OAE is applied.