New Scientist
A New York pilot found that adding olivine sand to the ocean could help lock away CO₂ without clear harm to seafloor life.
We may have a way to store more CO<SUB>2</SUB> in oceans without harming marine life
Author: Alec Luhn
ADDING olivine to the ocean could remove carbon dioxide from the atmosphere, and a pilot project in New York state found no signs of adverse effects on seafloor organisms.
This approach should still be carefully regulated, “but there might be ways that it could work and have a minimal effect”, says Emilia Jankowska at the non-profit group Hourglass Climate, who led the study.
Olivine, or magnesium iron silicate, is a greenish mineral common in Earth’s mantle. Once it comes to the surface, it tends to react with the CO2 dissolved in rainwater to form metals, silicates and bicarbonate, a stable compound that eventually flows into the ocean, locking CO2 away for thousands of years.
Spreading crushed olivine and other silicates on farm fields could speed up this process and remove up to 1.1 gigatonnes of CO2 annually, recent research found. But US start-up Vesta plans to add olivine directly to the ocean, where it would turn dissolved CO2 into bicarbonate and allow the ocean to absorb more CO2.
Olivine typically contains trace amounts of heavy metals, however, and lab studies have found elevated levels of nickel and chromium in crustaceans and molluscs exposed to it.
The addition of olivine to the ocean should be regulated, but there might be ways it could work
In 2022, Vesta deposited 650 tonnes of olivine sand along a beach in Long Island, New York state, on top of 13,500 tonnes of regular sand added to bolster the shore, which is being swept away as storms intensify. The tide and waves carried the olivine to sea.
The researchers scooped up sediment from the shallows out to 160 metres offshore before and after the olivine addition, and again a year later. They compared this to sediments near sections where only normal sand was added and where no sand was added.
Of dozens of species, only a tiny worm called the fringed blood worm significantly declined in the olivine area, and the overall abundance and diversity of bottom-dwelling species recovered within two months (CDRXIV, doi.org/q6xs). While the species composition changed, it also changed in the area where only normal sand was added, which suggests the common practice of beach nourishment was to blame.
Most importantly, concentrations of nickel, chromium cobalt and manganese in the organisms remained low.
Vesta conducted the environmental monitoring of the field trial, and Jankowska and the founder of Hourglass formerly worked for the company. But Hourglass received philanthropic funding from the Grantham Foundation to independently analyse the monitoring data.
However, the study’s claim of no adverse effects is “stronger than what the evidence shows”, says James Kerry at the non-profit group OceanCare. Fluctuations of olivine concentrations due to what the study called “burial- re-exposure cycles” meant the olivine might have been buried much of the time under the far larger quantity of normal sand deposited, he says.
“The lack of accumulation that’s apparent may reflect limited exposure, not necessarily that the material is intrinsically safe,” he says.
Credits: TCA, LLC.