A beach in Southampton, New York, treated with olivine sand
Chayenne Moreau
The inaugural experiment using crushed olivine to absorb atmospheric carbon dioxide in the ocean reported no negative effects on the seafloor ecosystem after its first year.
While these initial findings from the trial in New York state are promising for carbon removal, researchers caution that not all potential adverse effects may have been identified.
Emilia Jankowska from the non-profit Hourglass Climate, who led the study, emphasized the need for careful regulation of olivine addition to the ocean. She stated, “but there might be ways that it could work and have a minimal effect.”
The United Nations climate body has acknowledged the necessity of carbon removal strategies, including tree planting and CO2 filtration, to achieve net-zero greenhouse gas emissions. As emissions continue to rise and the target of limiting global warming to 1.5°C above preindustrial levels becomes increasingly difficult to attain, there is hope that these technologies might help cool the planet.
Olivine, a magnesium iron silicate, is a green mineral prevalent in the Earth’s mantle. When exposed to the surface, it reacts with CO2 in rainwater to form stable compounds like metals, silicates, and bicarbonate, which eventually flow into the ocean, sequestering CO2 for thousands of years.
Recent research indicates that spreading crushed olivine and other silicates on farmland could accelerate this process, potentially removing up to 1.1 billion tonnes of CO2 annually. However, the US start-up Vesta aims to add olivine directly to the ocean, converting dissolved CO2 into bicarbonate and enhancing the ocean’s ability to absorb atmospheric CO2.
Olivine typically contains trace amounts of heavy metals, and laboratory studies have shown elevated levels of nickel and chromium in crustaceans and molluscs exposed to it. There are also concerns about the sand potentially smothering bottom-dwellers like crustaceans, molluscs, snails, and worms.
In 2022, Vesta deposited 650 tonnes of olivine sand along a beach in Long Island, New York state, atop 13,500 tonnes of regular sand used to reinforce the eroding shoreline. The tide and waves dispersed the olivine into the sea.
Researchers collected sediment samples from the shallows extending 160 meters offshore before and after the olivine was added and repeated the sampling a year later. They compared these samples to those from sections of the beach where only regular sand was used or no sand was added.
Of numerous species, only the tiny fringed blood worm showed a significant decline in the olivine area, but the overall abundance and diversity of bottom-dwelling species rebounded within two months. Species composition changes were also observed where only regular sand was used, implying that beach nourishment practices contributed to these changes.
Importantly, levels of nickel, chromium, cobalt, and manganese in organisms remained low. Jankowska noted, “The natural system is just so dynamic that any dissolving constituents are very rapidly diluted.”
Vesta conducted the environmental monitoring for the field trial, and both Jankowska and the founder of Hourglass have previously worked for the company. Nonetheless, Hourglass received funding from the Grantham Foundation to independently analyze the monitoring data.
According to Christopher Pearce from the National Oceanography Centre in the UK, dissolving olivine in the ocean can promote the precipitation of calcium carbonate, which locks away trace metals. However, this process might also reduce the additional CO2 the seawater can absorb.
Pearce commented, “It’s a really critical study to move from lab-based understanding to real-world interactions. Further trials… will be important for understanding different biological responses… and different rates of [CO2] uptake.”
James Kerry from the non-profit group OceanCare argues that the study’s claim of no adverse effects might be overstated. He suggests that fluctuations in olivine concentrations, due to “burial–re-exposure cycles,” may have led to the olivine being buried under the larger quantity of regular sand. “The lack of accumulation that’s apparent may reflect limited exposure, not necessarily that the material is intrinsically safe,” he says.
Hourglass Climate is currently monitoring a larger trial in which Vesta submerged 8,200 tonnes of olivine 450 meters off Duck, North Carolina, in 2024. Preliminary results indicate that species abundance and diversity have recovered, while Hourglass continues to analyze metal accumulation, according to Jankowska.
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