Towards sustainability-aware carbon dioxide removal deployment

Carbon dioxide removal (CDR) technologies are increasingly considered a necessary complement to deep emissions reductions for meeting climate targets. However, large-scale CDR deployment involves trade-offs across multiple systems, including land, energy, water, and human health. Direct air carbon capture and storage is highly energy-intensive, while bioenergy with carbon capture and storage and biochar, are land-intensive. Enhanced rock weathering may also pose non-negligible human and environmental toxicity risks. Together, these trade-offs raise concerns about the sustainable scale of CDR deployment. This study applies the specific techno-economic logic of the global energy system model MESSAGEix to navigate these trade-offs. By incorporating spatially explicit constraints from the global land use allocation model MAgPIE, we assess how the MESSAGEix optimization framework responds to biodiversity intactness index targets and toxicity limits. The results within this specific modeling framework show that these constraints substantially alter both the composition and spatial distribution of CDR technologies. These findings highlight the importance of consistently aligning energy model topology with land-based sustainability impacts and demonstrate one potential pathway for regionally tailored CDR portfolios that align climate mitigation with broader sustainability objectives.