text: Calcium looping is considered as potential promising solutions to reduce CO  capture energy penalty. There are many advantages from the calcium looping methods. Firstly, the method has been proved to yield a low efficiency penalties (5-8% points) while other mature CO   capture systems yield a higher efficiency penalties (8-12.5%). Moreover, the method is well suited for a wide range of flue gases. Calcium looping is applicable for new builds and retrofits to existing power stations or other stationary industrial CO sources because the method can be implemented using large-scale circulating fluidized beds while other methods such as amine scrubbing is required a vastly upscale solvent scrubbing towers.  In addition, crushed limestone used in calcium looping as the sorbent is a natural product, which is well distributed all over the world, non-hazardous and inexpensive. Many cement manufacturers or power plants located close to limestone sources could conceivably employ Calcium looping for CO  capture. The waste sorbent can be used in cement manufacture.