Toward Credible Carbon Dioxide Removal: Harmonized Accounting and Data Gaps Across Six CDR Approaches

Carbon dioxide removal (CDR) is essential for achieving net zero and net-negative emissions, yet robust monitoring, reporting, and verification (MRV) remains a major challenge. Current accounting practices are fragmented, with inconsistent system boundaries and a narrow focus on carbon, overlooking wider environmental impacts and co-benefits. Drawing on five years of research and demonstration under the UK GGR-D Programme, the most long-term global MRV effort, with multiple years of monitoring across multiple CDR technologies, this study proposes a harmonized framework for defining system boundaries across six key CDR approaches: biochar, bioenergy with carbon capture and storage (BECCS), direct air capture with storage (DACCS), peatland restoration, enhanced rock weathering, and afforestation. We map data availability for evidencing net removal across full supply chains, including the capture of CO2 from the atmosphere and its final storage, and assess gaps in environmental impact data. Our findings show that harmonization is feasible across diverse CDR methods—land-based, engineered, and hybrid land-based - engineered—but data coverage is uneven, particularly for non-carbon metrics. These gaps pose risks for sustainability assessments and the credibility of CDR claims, with implications for emerging policy frameworks and carbon markets. This work provides actionable insights for developing robust MRV systems that support transparent, sustainable CDR deployment at scale.