Can These Rocks Help Rein in Climate Change? – Eos

by | Sep 27, 2022 | Climate Change

The world’s oceans play a key role in sucking up carbon from the atmosphere. Until anthropogenic carbon emissions began on a mass scale with the Industrial Revolution, ocean carbon uptake was one part of a land-ocean-atmosphere juggling act that kept the carbon cycle roughly in balance.

Now, a California-based company wants to use green sand to exploit the carbon sponge of the ocean to avoid the worst outcomes of global warming.

The Need for Speed

Vesta is a private company that believes it can speed up the ocean’s long-term carbon sequestration process by treating coastal areas with crushed olivine. Although high-quality olivine can be used as a gemstone (peridot), it is a relatively inexpensive mineral whose properties (it weathers very quickly) have long been studied as a means of enhanced weathering or ocean alkalinization, which some scientists have proposed as a way to mitigate climate change.

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In the natural process of weathering, rocks are broken down by phenomena such as rain and extreme temperatures. Rain absorbs carbon dioxide (CO2) from the atmosphere and forms bicarbonate ions when it reacts with rocks rich in silicate and magnesium, like olivine. The bicarbonate flows into the ocean, where it is ingested by marine organisms to create shells and exoskeletons; these shells as well as precipitates of the weathered minerals themselves can form limestone and other carbonates that store carbon for thousands of years. The bicarbonate also acts as a kind of antacid in the ocean, helping to fight ocean acidification.

In what Vesta describes as coastal carbon capture, the weathering process is accelerated by grinding large amounts of olivine into beach and seafloor sand, increasing the surface area of the mineral available for chemical reaction with seawater.

The idea isn’t new, and the environmental side effects are ambiguous. The operation would expend energy and, potentially, carbon emissions. Vesta has also partnered with the largest dredging company in the United States, raising questions about environmental impact to pelagic communities around the seafloor.

“While the idea of accelerating the Earth’s natural geological carbon removal …

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