An innovative system that reduces concrete waste generated at construction sites to zero has been put to practical use at the construction site of a large-scale production facility in Kumamoto Prefecture. This has been achieved by adding a simpledevice to the on-site wastewater treatment facility. After washing out and removing aggregate from waste concrete, the remaining cement slurry is passed through a special device producing ultrafine bubbles to efficiently absorb and mineralise CO₂. The recovered aggregate was reused as roadbed material for a passageway within the construction site. In the future, we aim to further reduce CO₂ emissions by capturing the exhaust gas from heavy machinery used on site and utilising it to treat waste concrete, thereby contributing to the realization of a decarbonized society.