CO2 fixation by artificial weathering of waste concrete and coccolithophorid algae cultures

For removal of industrially produced CO₂, we have proposed a new CO₂ fixation method which is combined with artificial weathering of waste concrete and coccolithophorid algae cultures. Waste concrete was suspended in sea water and weathered efficiently by supplying CO₂ to the suspension. During this weathering process, CO₂ was absorbed and dissolved into sea water. The maximum CO₂ absorption by the concrete suspension (100 g/l) was obtained as 1.5 (g CO₂)/l for 1 hr. Calcium contained in waste concrete was also dissolved in sea water. Coccolithophorid alga Emiliania huxleyi was cultured in a medium which was composed of the resulting sea water and contained sufficient dissolved inorganic carbon. Coccolith production and growth using this medium were enhanced to a greater extent than using Eppley's medium. During E. huxleyi culture, atmospheric CO₂ was absorbed, and dissolved inorganic carbon was fixed in CaCO₃ particles. These results demonstrate that atmospheric CO₂ can be absorbed and fixed permanently in the form of calcium carbonate and biomass by artificial weathering of waste concrete and coccolithophorid alga culture.