When CO2 is pumped into underground porous rocks, it combines with metal ions in the salty water that fills the rock pores and mineralizes into mineral carbonates, such as calcium carbonate (CaCO3). The process can take thousands of years. The team of researchers put a diverse mix of common bacterial species in a calcium chloride solution. After pumping in CO2, they noticed that calcium carbonate formed faster in areas where the bacteria were living than it did in sterile solutions. The CaCO3 also had a different mineral structure when the bacteria were around. The bacteria enhanced the formation of calcite even when they were inactive.
It turned out that the bacteria’s surfaces were accelerating the synthesis of CO2 with calcium ions. After genetically modifying one of the bacterial species, Caulobacter vibrioides, shaping its surface to attract calcium ions, more CaCO3solidified than in tanks with unmodified bacteria. Most of it solidified in the more stable crystalline calcite form likely to capture CO2 over geological time.
Cappuccio wants to test the modified bacteria at higher pressures and temperatures, and lower pH, conditions that might be found underground, where CO2 would be stored