Life-Cycle Assessment of Solid Calcium-Looping Direct Air Capture and Its Synergistic Dual Use for Net-Negative Cement

Calcium-looping direct air carbon capture and storage (DACCS) is a mature technology positioned for gigatonne-scale carbon dioxide removal (CDR). However, a holistic assessment of its system-wide environmental performance and large-scale implications remains critically absent. Here, we present a prospective life cycle assessment (LCA) of megatonne-scale calcium-looping DACCS systems under projected 2050 energy scenarios, evaluating CO2 removal alongside 18 other environmental impact categories. Our analysis confirms the high potential of calcium-looping DACCS, demonstrating net removal efficiencies ranging from 85% to 96% by 2050. Net removal of 1 GtCO2 increases other environmental impacts by under 2% of the global safe operating space in most scenarios. Environmental hotspots, including particulate matter formation, aquatic eutrophication, and freshwater ecotoxicity, are primarily dominated by the energy supply chain. We then demonstrate the substantial potential for the synergistic integration of calcium-looping DACCS with cement production, leveraging the dual-use of limestone as both a DAC sorbent and a cement feedstock. This integration offers dual benefits for CDR and industrial decarbonization. By cycling the CaCO3 sorbent once through the DAC unit before its calcination in the cement kiln, the integrated system achieves net-negative cement production with a final footprint of approximately -0.15tCO2 per tonne of cement. Subsequent sorbent cycles further reduce this footprint. These findings position calcium-looping DACCS not only as a competitive CDR pathway but also as a powerful solution for decarbonizing hard-to-abate sectors, offering a clear path toward achieving net-zero and net-negative cement production.