Assessing the net carbon removal potential by a combination of direct air capture and recycled concrete aggregates carbonation

Removing and storing CO 2 from the atmosphere has an important role in combating climate change. This study assessed the CO 2 removal potential of combining direct air capture with carbonation of recycled concrete aggregates (RCAs). An industrial-scale RCA carbonation process model quantified key parameters' impacts on carbonation duration and energy consumption. Furthermore, a lifecycle analysis evaluated scenarios of two cases: (i) using pure CO 2 with transportation between DAC and carbonation, and (ii) onsite production of low-purity CO 2 . For 90 % carbonation of 1 tonne of RCA, the performance of case-i scenarios ranged from ∼13 kg net CO 2 removal to ∼14 kg net CO 2 emission, influenced by DAC technology, transport option, and electricity carbon intensity. In case-ii scenarios, 1 % CO 2 feed purity achieved 70 % greater CO 2 removal than using pure CO 2 . This work provides an initial indication of the potential of this scheme while revealing key factors to investigate in future experimental exploration.