CO2 from the flue gases of a rotary kiln in a cement industry (CO2: 25 vol%) will be used for the production of value-added chemicals (acid additives for cement formulations) and materials (CaCO3 nanoparticles to be used as concrete fillers). A circular-economy-approach is enabled: the CO2 produced by cement manufacturing is re-used in a significant part within the plant itself to produce better cement-related products entailing less energy intensity and related CO2 emissions by a Quadratic effect.