Mining the atmosphere: A concrete solution to global warming

To neutralize anthropogenic climate impacts, excess carbon dioxide (CO 2 ) – about 400 Gt of carbon – needs to be removed from the atmosphere. After the energy transition is accomplished, we propose that excess renewable energy can be used to extract CO 2 from the atmosphere and convert it into methane or methanol, which are further processed into polymers, hydrogen, and solid carbon. End-of-life polymers are pyrolysed and part of the carbon is used to produce silicon carbide. Solid carbon and silicon carbide become then aggregates and fillers for concrete and asphalt. At the end of their lifecycle, landfilled construction materials become the final carbon sink. Up to 12 Gt of carbon could be stored per year, mostly as concrete aggregates. The synthesis of carbon-based materials in cycles of increased chemical reduction has multiple advantages, including long-term stability, high storage density of the carbon, decentralized implementation, and replacement of current CO 2 -emitting materials. Fig. A: Schematic representation of the proposed concept "Mining the atmosphere". Global activities (blue-shaded area): 1) CO 2 is captured with renewable energy; 2) H 2 is produced with renewable energy; 3) CH 4 or CH 3 OH are produced from CO 2 and H 2 ; 4) polymers are produced from CH 3 OH (and possibly from CH 4 ); 5) polymers and CH 4 are distributed through existing logistics chains. Local activities (green-shaded area): 6) CH 4 is pyrolysed to obtain H 2 for clean energy or methanation and solid carbon; 7) CO 2 is converted into biomass via photosynthesis, then pyrolysed; 8) waste polymers are pyrolysed; 9) carbon from all these different sources is converted into building materials; 10) carbon is combined with silicon to produce SiC, which is also used in building materials; 11) waste building materials end up in landfills, the final sink of the CO 2 from the atmosphere.