unpublished content -> the review on MRV will be added soon
Why it matters
The MRV review shows for what we have scientific evidence – and for what we do not have scientific evidence. It provides a baseline for future assessments of the scientific literature on CDR and allows more targeted and specific investigation on MRV of CDR. It moreover provides a benchmark for science based assessment of MRV practices.
Short summary
The review systematically maps the scientific literature on MRV of CDR to provide an overview of evidence patterns, knowledge gaps, and review the state of academic knowledge on MRV of CDR. Using robust search, screening, and inclusion strategies, the authors have identified almost 200 scientific studies providing insights for MRV of CDR. By mapping and reviewing these studies, knowledge hubs and gaps are shown, highlighting needs and providing entry points for future research.
Brief description of methods
For the MRV review, a systematic search approach was used to identify over 50,000 potentially relevant studies of which 12,000 were manually screened using a machine learning prioritization approach. After multiple rounds of screening, cleaning, and reviewing, almost 200 scientific studies were included in the work that where then analyzed along eight MRV related topics, such as quantification, removal quality, or governance. The systematic map is accompanied by a narrative review to synthesize best practices for the different CDR methods.
Key results
The review identified patterns and gaps in the scientific literature on MRV of CDR. It is shown that third of the literature on MRV of CDR focuses on the conventional CDR methods afforestation and reforestation, and soil carbon sequestration. Novel CDR methods, such as direct air capture, and marine CDR methods, such as blue carbon ecosystems, are rarely studies in the context of MRV. The majority of studies dealing with approaches to quantify carbon sequestration, while topics such as reporting or verification of CDR receives much less attention.
Future directions
MRV is an emerging topic and the literature body is rapidly growing which makes regular updates necessary. Our work could serve as a foundation for a living review. Furthermore, and besides academia, the authors aware that MRV schemes are already established in practice and knowledge exists beyond the scientific literature, e.g., in actors in the voluntary carbon market. Reviewing this knowledge would accomplish our review and further allow for synthesizing knowledge from science and practice to allow learning in both directions.