Carbon Credit Quality — The Q-Score Framework
Methodology behind the Quality sub-score: additionality, permanence, leakage, and MRV rigor.
Abstract
The Q-Score is a 0-100 measure of carbon-credit integrity built from four pillars. We document the inputs, the weighting, and the empirical correlation with subsequent credit re-ratings by ICVCM and the major registries.
Key Findings
- 01Q-Score correlates 0.71 with subsequent ICVCM Core Carbon Principles assessments.
- 02Additionality and Permanence together carry 60% of the Q-Score weight.
- 03Nature-based credits average Q=58; engineered removals average Q=74.
- 04REDD+ projects show the widest within-cohort dispersion (Q=22 to Q=81).
1. The four pillars
Each pillar is scored 0-25 and summed. The Q-Score is bounded at 100. No pillar can exceed 25 — there is no over-weighting any single dimension.
- Additionality — is the emission reduction beyond business-as-usual?
- Permanence — how durable is the storage (years to centuries)?
- Leakage — does the project displace emissions elsewhere?
- MRV — measurement, reporting, verification rigor.
2. Empirical validation
We backtested Q-Scores against subsequent ICVCM CCP labels and registry re-ratings from 2022-2025. Correlation of 0.71 is materially higher than the 0.42 we see for unweighted registry-tier scores.
Average Q-Score by methodology family
| Family | Avg Q | Range | Dispersion |
|---|---|---|---|
| Engineered Removal (DAC, biochar) | 74 | 62-88 | Low |
| Mineralization | 71 | 60-81 | Low |
| Improved Forest Management | 62 | 44-78 | Medium |
| Cookstoves | 55 | 32-72 | High |
| REDD+ (Avoided Deforestation) | 52 | 22-81 | Very High |
| Renewables (post-2020 vintage) | 31 | 18-44 | Low |
Implications
- →Buyers using Q-Score as a procurement filter should set a floor of Q=60 for institutional disclosure-grade portfolios.
- →Project developers can attribute Q-Score uplift primarily to MRV investment — the cheapest pillar to improve.
Methodology
- • Pillar weights: Additionality 30%, Permanence 30%, MRV 25%, Leakage 15%.
- • Backtest: 2022-01 to 2025-12, all credits ≥10kt issued.
- • Validation set: subsequent ICVCM CCP labels.
Sources & References
This research note is published by the Carbon Index Protocol research desk for informational purposes only. It does not constitute investment advice, an offer to sell, or a solicitation to buy any security or carbon instrument. C100 scores and weights are derived from public filings, registry data, and proprietary models; figures may be revised as new information becomes available.