LONDON • Scientists say they may have found a radical breakthrough to tackling climate change - by pumping heat-trapping carbon dioxide into the ground and turning it into stone.
The approach involves dissolving the gas with water and pumping the resulting mixture - essentially, soda water - down into certain kinds of rocks, where the CO2 reacts with the rock to form a mineral called calcite. By turning the gas into stone, scientists can then lock it away permanently, the New York Times reported.
The research, called the CarbFix project and led by Columbia University, was published in American journal Science on Thursday.
Scientists have for years talked about the need for carbon capture and sequestration, a process which involves removing carbon dioxide from a coal-burning power plant's smokestack, for example, and pumping it deep underground to keep it out of the atmosphere.
But the process had a spotty record. Among the concerns about sequestration is that carbon dioxide in gaseous or liquid form that is pumped underground might escape back to the atmosphere. Hence, storage sites would have to be monitored, potentially for decades.
But the new approach provides a cheaper and more secure way of burying CO2 from fossil fuel burning underground to prevent it from warming the planet, the scientists said.
"We need to deal with rising carbon emissions and this is the ultimate permanent storage - turn them back to stone," Dr Juerg Matter of the University of Southampton, who is lead author of the study, was quoted by The Guardian as saying.
One key to the approach is to find the right kind of rocks. Volcanic rocks called basalts are excellent for the process, because they are rich in calcium, magnesium and iron, which react with CO2.
The research was conducted for years in Iceland, a volcanic island made up mainly of basalt. The researchers and an Icelandic utility tested the technology using CO2 that bubbled up naturally with the hot magma that powered a geothermal electricity-generating plant.
In 2012, they pumped about 250 tons of carbon dioxide, mixed with water, more than 450m down into porous basalt. The CO2 was laced with a radioactive isotope and there were other compounds in the water that helped the researchers to trace its spread into the rock.
The early signs were encouraging: Among other things, a submerged pump that was used to obtain samples of the mixture as it spread underground stopped working after a while because it got gummed up by the resulting calcite.
Now, the scientists say they have found more authoritative evidence that the technology works. They found that about 95 per cent of the carbon dioxide was converted into calcite. More importantly, the conversion happened relatively quickly - in less than two years. Rapid conversion of the carbon dioxide means that a project would probably have to be monitored for a far shorter time than a more conventional sequestration site.
While there remain concerns about whether the technology will be able to be scaled up enormously, the researchers are hopeful because, they said, there is enough porous basaltic rock around, including in the ocean floors and along the margins of continents, to make the technology viable.
And they said that although the process requires vast amounts of water, siting a sequestration project in or near the ocean could potentially solve the water problem, as sea water would work just fine.
