A great deal of the carbon dioxide that our industry produces can be extracted at the source before it gets into the atmosphere, where it would otherwise act as a greenhouse gas, trapping solar radiation before it can radiate back out into space. While the gas can be trapped, storage becomes an issue, especially given the sheer tonnage that is emitted by power plants and factories across the globe. But a new process may allow CO2 to be processed into solid rocks, made up of stable compounds that won’t enter the atmosphere.
This new process was developed by a research team led by Juerg Matter, currently an associate professor of geoengineering at the University of Southampton, using a natural, but normally slow process called weathering of rocks, where CO2, dissolved in water as carbonic acid, chemically reacts with rocks to form solid carbonate compounds. "In a sense, you just mimic nature, just speeding up the process," explains study co-author Sigurdur Gislason, a research professor with the University of Iceland in Reykjavik.
The researchers compressed carbon dioxide that was captured from a power plant in Iceland to 25 atmospheres, then dissolved the compressed gas into water that was stored in subterranean boreholes — basically making the water into high-pressure soda water. The water was then pumped into a layer of porous volcanic rock 500 meters (1,640 feet) underground, where the carbonic acid in the water chemically reacted with the basalts that made up the rock. The result was the formation of a mixture of carbonates of calcium, iron and magnesium, solid compounds that can’t escape into the atmosphere.
This process may be limited to CO2 sources that are situated near basalt rock formations, such as those found in Indonesia or Japan, otherwise the gas will need to be transported to processing facilities using this process. The water used can be recycled, and while fresh water was used for the experiment, seawater should also work just as well, for regions where water is otherwise scarce. The team plans to continue their research, looking to scale up the process to accommodate industrial scales.