R-744, also known as CO2, is a natural refrigerant that can be traced all the way back to the 1850s. It began to see widespread usage in the early 1900s and 1920s but eventually declined due to the Great Depression and due to the high pressure that R744 operates under. In recent years it has seen a resurgence in usage mainly due to companies looking for a replacement for the high global warming HFC refrigerants such as 134a, 410A, and 404A.
R-744 has many benefits over other mainstream refrigerants. It does not have any Ozone depletion potential, it’s global warming potential is 1, it is non-toxic, it is non flammable, and it is far more efficient over it’s competitors.
It’s hard to say if CO2 will become the new mainstream refrigerant again or if it will be replaced another alternative refrigerant.