Eliminate CO2 by spreading crushed olivine powder in the ocean? The idea may seem to come out of a climate science fiction novel. However, it has been studied very seriously by several teams of scientists for several years. The first test carried out off the coast of New York State brought encouraging signals: this innovative technique does not seem to disrupt the marine ecosystem, at least during its first year of observation, reports New Scientist.
Today, carbon elimination technologies are increasingly central to achieving carbon neutrality. As global emissions continue to skyrocket, moving a little further away from the goal of limiting global warming to 1.5 degrees above pre-industrial levels, hopes are turning to these revolutionary technologies
Olivine is a green mineral composed of magnesium silicate and iron, naturally present in some rocks of the Earth’s mantle. When it reaches the surface, it reacts naturally with the CO2 dissolved in the rainwater to form metals – silicates and bicarbonate. In the ocean, this compound is capable of capturing carbon and locking it up for thousands of years.
According to several scientific estimates, the dispersion of crushed olivine and other silicates on agricultural land could eliminate up to 1.1 billion tons of CO2 each year. The American start-up Vesta wants to go even further, by offering to pour the olivine directly into the ocean. Problem: this mineral contains traces of heavy metals that may disturb marine fauna. In addition, this sand rich in magnesium and iron could suffocate marine organisms.
A first experiment conducted in 2022
It is precisely to answer these questions that the experiment was launched. In 2022, Vesta deposited 650 tons of olive sand along a beach in Long Island, New York State, in addition to the 13,500 tons of conventional sand used to strengthen the coastline. The tides and waves then transported the grains to the sea.
A year later, the researchers compared the sediments present in shallow water with samples from neighboring areas, free of olivine. The verdict has fallen: among the dozens of species observed, only one – the fringed blood worm – saw its population decrease in the area concerned. The concentrations of nickel, chromium, cobalt and manganese recorded in organisms remained low.
Caution however
« The natural system is so dynamic that the dissolved elements are very quickly diluted, » explains Emilia Jankowska, director of ecology for the organization Hourglass Climate, which participated in the experiment. However, experts remain cautious. The dissolution of olivine in the ocean could also promote the precipitation of calcium carbonate out of the water, with consequences still poorly understood.
« This study is essential to move from laboratory understanding to real-world interactions, » acknowledges Christopher Pearce, head of the marine biogeochemistry group at the National Oceanography Center in the United Kingdom. « Other tests are needed to understand the different biological responses as well as the different rates of CO2 absorption, » he says.
James Kerry, an expert at the NGO OceanCare, seems much more skeptical. He believes that the study remains too limited to conclude the safety of the technique. « The apparent absence of [olivin] accumulation could reflect limited exposure and does not indicate that the material is intrinsically safe, » he supports.
In the meantime, Hourglass Climate is now following the impacts of a much more ambitious project. In 2024, Vesta submerged 8,200 tons of olivine 450 meters off Duck, North Carolina. Preliminary results seem to show that the abundance and diversity of marine species have gradually recovered. Analysis of metal accumulation is still ongoing. It remains to be seen whether this mineral geo-engineering can really become a large-scale climate solution.
source : slate
