Carbon credit rating services that rate the quality of individual projects are relatively new to the voluntary carbon market. In line with this guide’s presentation of how to think about carbon credit quality, existing services typically provide nuanced ratings that distinguish relative quality on a sliding scale, often across different criteria and quality dimensions (e.g., additionality, quantification, permanence, exclusive claims, and avoidance of social and environmental harms).
In practice what these services do is interrogate projects in line with (some version of) the recommendations found in vetting carbon crediting projects directly. Some rating services offer bespoke ratings for individual clients.[1] Others may team up with specific platforms to make their ratings available, such as the Salesforce Net Zero Marketplace or Allied Offsets which host ratings from three credit rating companies (for some listed projects). In 2023, Carbon Market Watch published a review of existing services and how they conduct their ratings. However, (when this page was published in 2024) all such services were operated as for-profit companies that typically do not divulge the details of their rating methods, nor do they typically make their ratings publicly available.
Pros: Relying on individual project ratings, conducted by a rigorous and reliable rating service, is probably the strongest way to avoid lower-quality carbon credits (short of conducting one’s own project-level due diligence). Such ratings can help buyers avoid lower-quality projects that may slip through the standards and vetting processes of carbon crediting programs, and provide a more nuanced approach to assessing carbon credit quality than simply looking at methodology-level reviews. Looking at project-level ratings is perhaps the only reliable way to discover individual higher-quality projects in “higher risk” categories (see Annex 1).
Cons: Most rating services are operated by for-profit companies who treat their procedures as confidential intellectual property. Buyers therefore need to pay for these services, which can add to cost, and in some cases the rating methods may still not be transparent. In addition, as the Carbon Market Watch report referenced above makes clear, different services sometimes attach markedly different scores to the same projects. Some discretion may therefore still be warranted in relying on any particular service provider.
[1] Joppa, L., Luers, A., Willmott, E., Friedmann, S. J., Hamburg, S. P. and Broze, R. (2021). Microsoft’s million-tonne CO2-removal purchase — lessons for net zero. Nature, 597(7878). 629–32. DOI:10.1038/d41586-021-02606-3.