Scientists have been working together to reduce carbon emissions on a global scale and are looking for solutions to capture and store carbon dioxide (CO2). Now, a team of researchers have successfully turned CO2 into solid rock in just two years, offering a solution for the abundance of carbon in the atmosphere.
Published in the American Chemical Society journal Environmental Science & Technology Letters, the study spotlights the results of a field project in eastern Washington where researchers injected pressurized liquid CO2 into a basalt formation. Basalt is a fine-grained volcanic rock that formed from lava millions of years ago and has previously been found in lab studies to turn CO2 into carbonate minerals.
Carbon dioxide is the most abundant greenhouse gas—a gas that traps heat in the atmosphere and contributes to climate change—in the Earth's atmosphere. While CO2 naturally exists in the air, human activity has massively elevated its concentration. Currently, atmospheric CO2 is at the highest it has been in the past 400,000 years at about 0.04%, or 400 parts per million by volume (ppm).
The team at the US Department of Energy's Pacific Northwest National Laboratory in Richland, Washington drilled a well in the Columbia River Basalt formation. In 2013, they injected roughly 1,000 metric tons of CO2 into the well. When samples were extracted from it two years later, the researchers found that the CO2 had turned into ankerite, a carbonate mineral that keeps CO2 tucked away and out of the atmosphere.
A similar field project called Carbfix took place near the Hellisheidi geothermal plant in Iceland. Here, scientists pumped a smaller amount (250 tons) of a diluted solution—unlike the Washington project, which injected pure CO2, the Iceland project dissolved the CO2 in water and hydrogen sulfide—into volcanic basalt. The team, who published their findings in the journal Science, saw the CO2 mineralize in months. Within two years, more than 95 percent of the solution had turned into carbonate.
Since basalts are readily available throughout the world, the findings of these field projects suggest there is a potential solution for tackling carbon rates in the atmosphere around the globe. While promising, there are a few obstacles: it is unclear whether this process can be scaled up to handle the some 40 billion tons of CO2 emitted each year, capturing carbon is expensive and scientists don't know for sure if the efficiency of the chemical reaction in basalt will remain if large amounts of carbonate exist underground.