CO₂ – Quo Vadis? If CO₂ emission is really an ecological indicator of green production?

Reduction of CO₂ emission has been a main topic in all sectors of our life for many years, and one of the most important milestones in a lot of companies, like in the building sector. It is commonly known that carbonation of building materials based on cement and lime is a natural process. Due to this fact, these materials can be eco‐friendly because they can absorb CO₂ from the atmosphere. Autoclaved aerated concrete sample with a density class 600, from different producers, and with different compressive strengths: 3.0, 4.0, and 5.0 N/mm², and density class 500: 2.5 and 4.0 N/mm² were the subject of this research program. The analysis of phase composition and observation under SEM microscope clearly showed the correlation between compressive strength and the amount of calcium silicate hydrates (C‐S‐H phase) formed under hydrothermal conditions, mainly tobermorite. Tobermorite content in AAC depends on the amount of binder used for its production. The performed calculations showed that not always the material with the lowest carbon footprint is the most eco‐friendly product because when looking at CO₂ emissions, one can forget about rational management of natural resources.