Provide is a carbonated cement slurry production system capable of efficiently fixing carbon dioxide in a cement slurry with a larger amount. A carbonated cement slurry production system for producing a carbonated cement slurry formed by carbonation of a cement slurry containing cement and water by a carbon dioxide-containing gas, the carbonated cement slurry production system including: a carbonation apparatus for bringing the cement slurry into contact with the carbon dioxide-containing gas; and carbon dioxide-containing gas supply apparatus for supplying the carbon dioxide-containing gas to the carbonation apparatus at a pressure larger than an atmospheric pressure, wherein the carbonation apparatus includes a carbonation tank for storing the cement slurry and the carbon dioxide-containing gas so that a gas phase formed of the carbon dioxide-containing gas is positioned above a liquid phase of the cement slurry.

Methods, systems and compositions for storing carbon dioxide in soil are disclosed herein. In some embodiments, the composition comprises at least 35% of cement by weight of the composition; 1-15% of lime by weight of the composition; at least 5% of a supplementary cementitious material (SCM) by weight of the composition; and carbon dioxide, wherein a weight by composition of the carbon dioxide is less than 5%. The composition can further comprise at least 35% of calcium carbonate by weight of the composition.