Some Bacillus bacteria can convert CO2 into rock in extreme environments.

David Marchel/Getty Images

Bacteria may be able to catalyze the mineralization of carbon dioxide under extreme conditions. Injecting such microbes underground with captured CO2 could lead to more sustainable greenhouse gas storage.

Gokce Ustunisik at the South Dakota School of Mines and Technology and his colleagues were isolated. Geobacillus Bacterial species from a compost pile in Washington state that were known to tolerate high temperatures and pressures.

In laboratory tests, the researchers compared the rate at which CO2 is demineralized when dissolved in water with and without these microbes. They tested the process at different temperatures, pressures and salinities, which were comparable. Extreme conditions were found deep underground. Where CO2 can be stored. They also tested the process with different types of basalt rock.

Without microbes, the researchers did not observe CO2 mineralization. Ustunisik says the process typically takes years, even under ideal geological conditions. “It’s taking forever,” she says.

When microbes were present, however, Ustunisik says it took only 10 days for CO2 to form mineral crystals at 80 °C (176 °F) and a pressure about 500 times that of sea level. In extreme conditions CO2 in excess of this rapid rate can be locked up in storage sites deep underground, such as depleting oil and gas reservoirs.

Ustunisik says the key to this rapid mineralization rate is an enzyme produced by bacteria called carbonic anhydrase. Once the CO2 solution dissolves the rock, she says, the enzyme rapidly reduces the acidity of the solution to allow magnesium and calcium carbonate minerals to leach from the rock.

Brett LingwallAt the South Dakota School of Mines and Technology, they also say that surface-dwelling microorganisms usually make this enzyme — humans do, too — but they usually don’t. Don’t live long in extreme conditions. “Life is tough 5,000 feet below the ground,” he says.

The researchers came up with something. Details of work at the annual conference of the American Geophysical Union in San Francisco in December. However, they are waiting to release more information — such as the exact species of bacteria they tested — until they receive a patent.

The researchers also plan to test. Bacillus Bacteria were isolated from deep in a former mine shaft in South Dakota, along with genetically modified strains, to identify which microbes performed best. Ustunisik says the next step after that is to test the microbes in one. Original storage well. But outside researchers say many factors cannot be translated.

“There are open questions around the resilience of these organisms, the food sources of these organisms, their turnover rates and their ability to function in different alkaline environments,” he says. Grishma Gudi Kota at Cornell University in New York. Nutrients will need to be injected with microbes to keep them alive. She says it can also be difficult to control how microbes spread across the Earth’s surface, which can be a particular concern if they are genetically modified.

Andrew Mitchell Aberystwyth University in the UK says it’s hard to know how fast microbes will catalyze CO2 mineralization on a large scale, but it would be “early” to reduce the process to 10 days. Finding a microbe that can catalyze minerals and survive deep conditions, he says. “A lot of insects don’t like high-temperature, high-pressure environments.”

Article modified on 14 February 2024.

We specified which bacteria were tested for mineralization activity.