Dusting the Ocean with Olivine: An Effective Method for Climate Engineering?

Abstract:

As a preliminary experiment, a low-cost method to determine the capacity of water to take up carbon dioxide was used. Several factors affecting the solubility of CO₂ in water were tested. Among the factors tested was the presence of olivine, a mineral used to enhance the uptake of CO₂ by soils through a process called Enhanced Weathering. Literature search indicated that olivine increases the alkalinity and concentration of silicate in water and thus increasing the capacity of water to take up CO₂. This, however, could not be verified with the said method. Albeit, further experiments showed that the concentration of silicate in distilled water with olivine increases if the water was acidified with CO₂.

In an additional investigation, to different types of water (distilled water, Baltic seawater (15 ppt) and North Atlantic Seawater (35 ppt)), powdered olivine was added in a concentration of 1g/litre. These were treated with different concentrations of CO₂ (400,800,1200 ppm) at 15°C. 400 ppm is the present concentration of CO₂ in the atmosphere. Alkalinity, pH, silicate and magnesium concentrations were monitored for a period of 10 days. To test if the silicate released from the dissolution of olivine promotes the growth of phytoplankton, the diatom, Phaeodactylum tricornutum, was cultured in the Baltic seawater used for the above experiments and Chlorophyll a concentrations were measured.

First results show that the effectiveness of olivine in increasing the alkalinity, pH, silicate and magnesium concentrations is limited only in the distilled water sample. This may be due to other ions in seawater which might be interfering in the dissolution of olivine. The powdered olivine sank immediately to the bottom of the containers, indicating that this does not stay long in the water column to cause any significant changes in CO₂ uptake, which occurs primarily in the surface of the ocean.