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

Removing and storing CO₂ from the atmosphere has an important role in combating climate change. This study assessed the CO₂ 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 CO₂ with transportation between DAC and carbonation, and (ii) onsite production of low-purity CO₂. For 90 % carbonation of 1 tonne of RCA, the performance of case-i scenarios ranged from ∼13 kg net CO₂ removal to ∼14 kg net CO₂ emission, influenced by DAC technology, transport option, and electricity carbon intensity. In case-ii scenarios, 1 % CO₂ feed purity achieved 70 % greater CO₂ removal than using pure CO₂. This work provides an initial indication of the potential of this scheme while revealing key factors to investigate in future experimental exploration.