Carlos Solis
A common green mineral could help turn oceans into long-term carbon sinks. Olivine is a green silicate mineral that’s common in nature. When rain or seawater reaches olivine, the mineral reacts with dissolved CO2 and converts it into bicarbonate — a stable form of carbon that can remain in the ocean for thousands of years.
Some estimates suggest spreading crushed silicate rocks on agricultural land could remove up to 1.1 billion tons of CO2 a year. Supporters say coastlines and shallow waters could speed the process because waves constantly mix and grind the mineral. As Teresa van Dongen, who founded the materials library Aireal, wrote: “One ton of olivine sand can absorb up to one ton of CO2 — under favorable conditions. You just spread it, and nature will do the rest.”
What They Found on Long Island
In 2022, researchers added crushed green olivine to a beach in Southampton, New York, to test whether the mineral could help the ocean absorb more carbon. They then let the waves carry the material toward shore and watched what happened to animals living in the sand.
Researchers sampled benthic sediment and animals before the addition, immediately afterward, and again a year later — from the nearshore out to 160 meters from the beach. They compared plots with olivine, plots with only ordinary sand added, and untouched control plots.
The sediment community experienced stress after the nourishment, but it recovered relatively quickly. The study found that abundance and species richness returned to control levels in roughly two months. Overall diversity and evenness did not change much.
One small species, the fringed blood worm, declined sharply in the olivine plots, but similar declines also appeared on plots that received only regular sand. That pattern suggests that the act of adding sand to the beach was likely the main disturbance, not olivine itself.
Analyses of metal content also looked reassuring: levels of nickel, chromium, cobalt, and manganese stayed comparable across sites for about a year, and animals collected from the plots did not show accumulation of those elements.
Proceed With Caution
Critics emphasize that the evidence remains limited. Claims that there were no negative effects may overreach what the current data support. Part of the problem is that olivine sometimes ended up buried under much thicker layers of ordinary sand, so animals may have had limited exposure to the mineral. In that case, the lack of metal buildup could reflect low exposure rather than proof that olivine is inherently safe.
Real-world conditions complicate the picture: waves repeatedly expose and then bury the material, ordinary beach sand can mask the experiment, and extracting, crushing, and transporting large volumes of olivine will produce their own emissions. Researchers also need better methods to measure how much carbon the ocean actually removes. Local communities may oppose plans to spread green sand along their shorelines.
The Experiment Continues
Hourglass Climate is now monitoring a larger experiment that Vesta ran off Duck, North Carolina, in 2024: the company placed 8,200 tons of olivine in the sea. Initial results suggest abundance and diversity recovered there as well, but metal analyses are still underway.
So far, olivine passed this first small marine test better than some critics feared. But one year on one beach does not deliver a final verdict on using the approach as a global climate policy tool — it is just the beginning of a much longer experiment.
Based on reporting from ZME Science
