🌊 From millennia to a few hours: they accelerate a carbon capture process

An Israeli laboratory is opening a new pathway for carbon sequestration by harnessing the millennial action of rock and water. This approach, inspired by a fundamental geological cycle, could offer heavy industries a complementary tool to mitigate their environmental impact. It does not rely on complex chemical compounds, but on accelerating a natural reaction between industrial gases, seawater, and common minerals.

The research conducted jointly by the Hebrew University of Jerusalem and the Open University of Israel tackles a central challenge: how to significantly improve a terrestrial carbon regulation process so that it meets the current climate emergency. By transposing this slow phenomenon into a controlled laboratory system, scientists were able to dissect its mechanisms and identify the key parameters to radically increase its speed.

Mechanics of an accelerated natural process

Carbonate weathering is a planetary climate regulator. Carbon dioxide present in the atmosphere dissolves in precipitation, forming a weak acid. This slightly acidic water then flows over rock formations such as limestone, gradually dissolving calcium carbonate. The reaction produces bicarbonate ions, a dissolved form of carbon transported by rivers to the oceans for long-term storage.

This geochemical cycle, although fundamental, operates on timescales incompatible with the pace of anthropogenic emissions. To compress it from several millennia to a few hours, the researchers designed a transparent experimental reactor. Inside, seawater and CO₂ circulate continuously through a bed of crushed rock, recreating and artificially intensifying natural conditions.

The study, published in the journal Environmental Science & Technology, details how precise control of physicochemical parameters makes it possible to optimize the reaction. Efficiency depends notably on the ratio between the gas and seawater. Moderate recirculation of CO₂ improves its incorporation, while too aggressive a flow can hinder the process. The size of the rock grains also influences the outcome.

Prospects for industrial application

The system demonstrated its ability to convert approximately 20% of the injected CO₂ into dissolved inorganic carbon. This margin indicates significant potential for optimization through engineering. Dolomite proved to be a particularly interesting material, as it appears to avoid the formation of secondary precipitates that could re-release carbon, thus offering a more stable sequestration pathway.

Power plants, especially those running on fossil fuels, constitute an obvious application target. Integrating reactors inspired by this principle downstream of smokestacks could allow for the treatment of a portion of flue gases. The process would use seawater and abundant rocks, resources accessible for many coastal facilities.

Other heavily emitting sectors, such as cement or steel production, could also adapt this technology. It proposes an alternative or a complement to more energy-intensive capture methods. The authors emphasize that this approach aims to integrate nature-inspired solutions into existing industrial infrastructure, offering a pragmatic path for emissions reduction.

To go further: How is carbon stored in the ocean?

The ocean acts as a giant sponge for carbon dioxide. At its surface, CO₂ present in the air dissolves directly into the water, an exchange facilitated by the movement of waves and wind. Once in seawater, a portion of this gas transforms into carbonic acid, then splits into bicarbonate and carbonate ions. This ensemble forms what scientists call dissolved inorganic carbon, the first form of oceanic storage.

The circulation of water masses then plays an essential transporter role. Surface waters, loaded with dissolved carbon, cool near the poles, become denser, and plunge into the depths. This phenomenon carries carbon toward the deep ocean layers where it can remain isolated from the atmosphere for centuries. It is a slow but very large-scale sequestration process.

In parallel, marine life operates a "biological pump." Phytoplankton, tiny algae, absorbs dissolved CO₂ to perform photosynthesis at the surface. Upon dying, a portion of these organisms and the waste from the animals that consume them sediment toward the seabed. A fraction of this organic carbon is thus buried in sediments, constituting very long-term storage, on the scale of thousands of years.