As can be seen from the above figur

As can be seen from the above figure, the density of carbon dioxide generally increases with the increase of pressure and decreases with the increase of temperature. In liquid state, the density can exceed 1000 kg/m, while in gas state, the minimum density can be close to 45 kg/m, so the density state can be controlled by controlling the pressure and temperature. When carbon dioxide is in liquid state, the density is the highest, and when the temperature increases, it enters the gas state, the density of carbon dioxide decreases rapidly. However, with the further increase of temperature and pressure, when it enters the supercritical state, its density will increase rapidly, although it is less than that of the liquid state, but it is far greater than that of the gas state. The supercritical state is easier to realize than the liquid state, so it is easier to realize in large-scale applications. Because of its higher density, it is more efficient than the gas phase and is beneficial to pipeline transportation.