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These researchers want to turn CO₂ into stone

Nature got there first: When CO₂ reacts with volcanic rock, it transforms from a greenhouse gas into solid minerals.

CO2 storage here? Marija Rosenqvist (in front) and Rakul Johannesen on fieldwork in the Faroe Islands.

CO₂ storage here? Marija Rosenqvist (in front) and Rakul Johannesen on fieldwork in the Faroe Islands.

(Photo: Njord / University of Oslo)

Hilde Lynnebakken COMMUNICATIONS ADVISER

Presented by: University of Oslo

Published 28 June 2025 - 00:01

We have to go back 55 million years. That was when Greenland and Norway began to drift apart, causing the Atlantic Ocean to open up. The Earth's crust between them became thinner and thinner, and enormous amounts of lava poured forth.

At the same time, the Earth suddenly became dramatically warmer. This chapter in Earth's climate history naturally interests geologists. In 2021, they sent a research ship out into the sea to collect samples from the seabed.

Some of the samples ended up with PhD candidate Marija Plahter Rosenqvist. She is not trying to figure out why it got so warm in the 'old days,' but rather how we can prevent it from suddenly becoming as warm now.

The researchers are investigating whether we can store CO₂ (carbon dioxide) in the lava rock that was formed when the Atlantic Ocean came into being.

Rosenqvist's sample of dark grey rock has holes in some places, somewhat like a chocolate bar with air bubbles. In other parts, it appears that the holes are filled with a lighter type of rock.

Marija Rosenkvist with a sample of lava rock from the seabed.

CO₂ in solid form has many advantages

The rock is basalt, the most common type of lava rock on Earth. The white spots are formed where CO₂ has reacted with volcanic rock and transformed from gas into minerals.

Researchers at the University of Oslo's Njord Centre are studying how this process occurs naturally. The goal is for this to become part of the solution to the climate problem.

“Storing CO₂ in solid form has many advantages. We don't need to monitor the reservoir over a long period since it doesn't leak,” says Rosenqvist.

The method also has great potential.

“More than 60 per cent of the Earth's surface is covered by basalt, so in theory, there is enough space for all the CO₂ we want to dispose of,” she says.

The principle is not entirely untested. The Carbfix project in Iceland serves as an inspiration for researchers in Oslo. However, there is one major difference: The basalt used in the Iceland project is fresh and porous, whereas in the North Sea, it's 50 million years old.

“To understand whether we can do this in places other than Iceland, we need to conduct more studies,” says Rosenqvist.

Perhaps it is possible to store CO2 as stone in the Faroe Islands? In any case, the geology of the Faroe Islands is part of the same basalt regions as in the North Sea. Rakul Johannesen has a background from the archipelago herself. — Perhaps it is possible to store CO₂ as stone in the Faroe Islands? In any case, the geology of the Faroe Islands is part of the same basalt regions as in the North Sea. Rakul Johannesen has a background from the archipelago herself.

The basalt from the North Sea can be found above sea level in the Faroe Islands

In the same office sits Rakul Maria Ingunardóttir Johannesen.

Together, they have been to the Faroe Islands equipped with drones, among other tools, to map the geology.

“The Faroe Islands are interesting because we find the same basalt here as we do out in the North Sea,” says Johannesen.

It might also be possible to store CO₂ on land here.

The researchers have mapped the geology of the Faroe Islands using drones.

“We already store CO₂ in reservoirs in the North Sea, but that's in sandstone,” Johannesen explains.

“Basalt is very suitable because it quickly reacts with CO₂ and forms solid minerals,” she adds.

A bit further down the corridor, we meet Paiman Shafabakhsh, who has almost been on a European tour with basalt samples.

What happens in the small pores of the rock?

While Johannesen studies geological formations and their fracturing, Shafabakhsh is focused on understanding what happens on a smaller scale, in the small pores of the rock.

“We inject CO₂ and fluid into the rock samples and want to know what occurs within the rock during this process,” he says.

To achieve this, the researchers scan the rock with X-rays and neutrons.

“With X-ray images, we can see the hard minerals, similar to a CT scan with bone fractures. Neutrons give us an image of the fluid that flows in the pores of the rock,” says Shafabakhsh.

A neutron image of an arm would show the blood flowing through the veins, but it would be harmful to humans.

He has examined these rock samples at two laboratories in Grenoble, France, and Zurich, Switzerland. Both are synchrotrons, machines that combine X-rays and neutrons.

Here is Paiman Shafabakhsh in the control room at PSI in Switzerland with collaborator Benoit Cordonnier from ESRF in France.

Shafabakhsh says that people in the industry often ask why they study the process on such a small scale.

“Traditional models that only look at field scale tend to overestimate the reactions taking place in the field. So to get an accurate picture, we need studies on a small scale,” says Shafabakhsh.

He adds that industry will face significant problems with CO₂ leaks if they do not take into account what happens on a small scale.

Researchers in the basalt project are also conducting idealised experiments on how CO₂ moves in the pores of basalt.

A laboratory model illustrates the principle

In the basement of the Physics Building, Yao Xu has 3D-printed models of rock into which they can inject CO₂ and fluids to study the patterns in which CO₂ moves in detail.

“CO₂ has its own personality. The gas has things it likes and dislikes. It likes water,” says Xu.

He injects CO₂ at the top of his setup. CO₂ reacts with water and becomes heavier, causing it to naturally sink downward.

Xu can adjust pore size and the rate at which he injects the CO₂ gas. A camera takes a picture every 30 seconds during the six-hour duration of each experiment.

CO2 is invisible, so Yao Xu uses a glass of water to check that there is gas in the system. — CO₂ is invisible, so Yao Xu uses a glass of water to check that there is gas in the system.

The results from the lab experiments and measurements on rock samples will eventually be compiled and compared with the work being done on the field scale.

From nanoscale to entire reservoirs

Project leader Francois Renard explains that the amount of CO₂ that will react with the rock, and thus how much can be stored, depends on how porous the rock is. This depends on the minerals it contains, its permeability, and a variety of other properties.