An NGO wants to use “green sand” to capture a large amount of CO2. The idea is to spread it on the sand of the beaches to capture carbon dioxide.
A very interesting process
Olivine is a mineral from the group of silicates. Abundant in certain parts of the globe such as Hawaii or Reunion, olivine is used as a fine stone in jewelry. An article published in the MIT Technology Review on June 22, 2020 refers to the American NGO Project Vesta wanting to use it to capture CO2. Founded in 2019, the latter aims to capture all annual human CO2 emissions! According to the organization, this goal could be achieved by covering only 2% of the world’s beaches with olivine.
An astonishing geo-engineering process will be implemented, namely forced alteration. The latter is a natural process by which CO2 in the atmosphere is stored by marine organisms in the form of limestone. Thus, olivine, rich in silica and magnesium, is transformed into powder by the action of waves. Then, water and CO2 degrade it into silicates and carbonate ions.
Finally, carbonates become calcium in the shells and skeletons of molluscs, or even in corals. When these die, the CO2 is found permanently stored at the bottom of the oceans.
Some difficulties on the horizon
The NGO estimates that one ton of olivine can absorb up to 1.25 tons of CO2. In addition, the compounds produced are alkaline, which allows a reduction in ocean acidification. However, this is one of the unfortunate consequences of climate change.
In addition, it should be known that forced alteration had been conceptualized in a study published in Nature in 1990. The Swiss researcher W. Seifritz already proposed to use silicates to capture CO2. Subsequently, other studies have emerged, with interesting figures and conclusions. On the other hand, this process has never really been implemented until today.
Although forced alteration seems very simple in theory, its realization nevertheless encounters some difficulties. First, the olivine is trapped in other rocks, so it must be extracted. The good news, however, is that ore is abundant on Earth and is mined in quantities like that of coal. However, the process carried by Project Vesta is to bring the olivine to the beaches and wait for it to turn into powder.
Finally, if the degradation of olivine allows the capture of CO2 and the reduction of ocean acidification, there is a perverse effect. Indeed, the dissolution of a large quantity of materials – especially silica – could impact ecosystems. For example, there may be a question of a proliferation of phytoplankton at the origin of anoxic zones, deprived of oxygen. It is therefore necessary to know more about these risks before possibly implementing this project.