Assess and compare the effectiveness, risks, costs, permanence, and scalability of four major carbon dioxide removal (CDR) approaches—direct air capture (DAC), bioenergy with carbon capture and storage (BECCS), afforestation/reforestation, and enhanced rock weathering. Evaluate carbon removal capacity (per unit area, energy or biomass), lifecycle emissions, resource and land/water impacts, ecological and social risks, technological readiness, economic feasibility, and monitoring/governance challenges. Require reasoned judgments supported by quantitative estimates, trade-off analysis, and discussion of uncertainties and policy implications.