Capturing and storing greenhouse gases beneath the earth could allow climate change to be mitigated, but researchers still need to find a method that can both permanently and safely contain the gases. Now researchers at the Pacific Northwest National Laboratory (PNNL) believe that they may have found an option: they've begun injecting carbon dioxide (CO2) — one of the main gases involved in global warming — a half-mile underground into flows of basalt, a volcanic rock, to see if it will stay put. PNNL's researchers suggest that because basalt is porous, it'll be able to hold onto CO2 when it's inserted in a liquid form. According to Nature, the basalt should also initiate a chemical reaction that will ultimately turn the mixture into limestone — though the process will take decades.

"We are returning the carbon dioxide from whence it came."

PNNL has had success combining CO2 and basalt in the lab, and its researchers are now heading out for field trials. At a location in Washington, the researchers have injected 1,000 tons of CO2 into basalt flows beneath the land. The research's leader, Pete McGrail, said that their early studies have "conclusively demonstrated" that basalt and CO2 will "quickly react" to form minerals and solid rock. Nature notes that scientific opinions still diverge on whether underground storage of greenhouse gases is a good idea, but McGrail believes that it's only natural. “We are returning the carbon dioxide from whence it came," he told Nature.

To ensure that the CO2 doesn't escape from basalt during its early time underground, a layer of solid rock will be placed above it as a seal. The researchers will extract samples from the basalt over the next 14 months, checking to see how the CO2 has reacted. McGrail says that this is just the first step for PNNL, but if his team or another group of researchers can find a method that works, it could be used to drastically cut down on greenhouse gases being released into the atmosphere: a report from the US Department of Energy found that the United States and Canada may be capable of holding 900 years worth of CO2 emissions beneath the earth.