Voluntary Carbon Markets (VCM)

• Voluntary Carbon Markets are non-mandatory, project-based platforms that trade 1 tCO₂e credits from verified climate projects like reforestation and renewable energy.
• They mobilize climate finance for net-zero strategies while grappling with challenges such as additionality, permanence, leakage, and double counting.
• Digital innovations, including blockchain-based registries and automated MRV, enhance transparency and efficiency in credit issuance, tracking, and retirement.

Voluntary Carbon Markets (@@@@1@@@@) are non-mandatory, project-based marketplaces that allow private actors—including corporations, institutions, and individuals—to purchase carbon credits that represent claims to greenhouse gas (GHG) mitigation outside regulated cap-and-trade or carbon tax regimes. These markets have expanded as complements to compliance markets, serving as a means for entities to address residual emissions, support climate finance, and bolster “net-zero” strategies. However, the efficacy, integrity, and system design of VCMs have been subjects of intensive empirical scrutiny and systemic critique (Salguero, 7 Dec 2025, Jaffer et al., 2024, Baiz, 2024).

1. Fundamental Concepts and Structural Overview

In VCMs, a carbon credit is defined as a tradeable unit corresponding to 1 metric ton of CO₂-equivalent (tCO₂e) either avoided or removed, originating from verified mitigation projects such as reforestation, REDD+, renewable energy, methane destruction, or improved cookstoves (Salguero, 7 Dec 2025, Baiz, 2024). Credits are tracked via registries—centralized or digital ledgers—that issue, record, transfer, and retire credits. Retirement, the act of rendering a credit ineligible for further trade, is required to substantiate offset claims and prevent double counting.

The distinction between VCMs and compliance markets is foundational: VCMs operate without direct regulatory mandate, focusing on voluntary offsetting of GHG emissions, while compliance markets are structured by law, imposing emission ceilings and requiring regulated allowances. VCMs have become pivotal for mobilizing climate finance in contexts where compliance price signals are weak or absent (Salguero, 7 Dec 2025, Baiz, 2024).

2. Integrity Challenges: Additionality, Permanence, Leakage, and Double Counting

VCMs are subject to four primary and empirically validated integrity challenges, which sharply limit the real climate impact of most credited projects (Salguero, 7 Dec 2025):

1. Additionality: Credits are only environmentally meaningful if the associated mitigation would not have occurred absent carbon-market finance. The difference between baseline emissions and project emissions,

$$\Delta E = E_{\text{baseline}} - E_{\text{project}},$$

defines additionality. Empirically, only 16% of issued VCM credits are found to be genuinely additional, implying that 84% represent activities (e.g., pre-planned renewables, low-deforestation-risk forests) that would have occurred anyway.

2. Permanence: Many mitigation actions face risk of reversal (e.g., forest fires, disease, illegal logging). The permanence risk factor,

$R_p = 1 - e^{-\mu T},$

(where $\mu$ is the annual reversal probability and $T$ is duration) is often underestimated. For forest-based VCM projects, $R_p$ can exceed 0.64 over 20 years; buffer pools seldom match this risk.

3. Leakage: Reductions within a project boundary can increase emissions outside ("leakage"), offsetting net benefit. The leakage ratio,

$$\lambda = \frac{\Delta E_{\text{outside}}}{\Delta E_{\text{project}}},$$

can reach values above 1.0 in REDD+ meta-analyses, meaning a suppression in one area can cause greater increases elsewhere.

4. Double Counting: Without centralized and unique serial-numbered tracking, two entities can claim the same unit. The double-counting risk is realized as

$$\text{Double counting risk} = \begin{cases} 1, & \text{no unique retirement tracking} \ 0, & \text{unique serial, publicly retired} \end{cases}$$

Overlaps between registries, as well as concurrent “net-zero” corporate claims for the same credit batches, are routinely documented.

These integrity challenges drive systematic overestimation. The “Offset Achievement Ratio” (OAR),

$$\text{OAR} = \frac{\text{Real, additional, permanent reductions}}{\text{Credits issued}},$$

is empirically $<$16% for VCMs, with even lower values in certain project categories (e.g., wind/IFM OAR $\approx 0$%) (Salguero, 7 Dec 2025).

3. Digital Innovation and Blockchain Architectures

Recent work proposes digital architectures to address transparency, standardization, and the integrity failures endemic to legacy VCMs (Jaffer et al., 2024, Saraji et al., 2021, Baiz, 2024). Core advances include:

• Reproducible, Computable Carbon Accounting: Pipelines—such as the “$(A-L)\times eP$” method central to the PACT stablecoin—use open-source econometric and remote-sensing workflows to derive net avoided emissions. This includes:
  • Comparing remote-sensed carbon stocks in treatment and control pixels,
  • Quantifying leakage using matched local zones,
  • Discounting by an equivalent-permanent factor, $eP$, based on projected carbon release schedules over long horizons,

$\mathrm{PACT\ tonnes} = (A - L) \times eP,$

with all inputs and results anchored to IPFS and exposed on-chain (Jaffer et al., 2024).

• High-Integrity Digital Assetization:
  • On-chain smart contracts (e.g., Tezos FA2-compliant registry, pool, and custodian contracts in PACT) ensure transparent issuance, transfer, and retirement of uniquely identified carbon assets (Jaffer et al., 2024).
  • Pooling creates fungible asset classes based on co-benefit tags (biodiversity, livelihoods, justice), harmonizing liquidity and qualitative attributes.
  • Multi-sig verifiers and automated market makers (AMM) create trust-less, efficient environments for credit tokenization and trading (Saraji et al., 2021).
• Scalability and Data Quality:
  • Automated digital MRV (Measurement, Reporting, Verification) pipelines and public audit trails drive down manual transaction costs and facilitate near-real-time market operations with low energy use and negligible carbon footprint per transaction (Jaffer et al., 2024, Saraji et al., 2021).

4. Standards, Registries, and Interoperability

Market harmonization and trusted operation require robust standards and registry models (Baiz, 2024):

• Core Carbon Principles (CCPs): As defined by the Integrity Council for the Voluntary Carbon Market (ICVCM), these provide baseline requirements for project eligibility, third-party validation, and registry behavior.
• Decentralized Meta-Registries: Initiatives such as IETA/World Bank/CAD Trust use permissioned blockchain infrastructures to interlink national and private registries, enforce unique credit identifiers, and guarantee interoperable, transparent metadata.
• Interoperable Data Models: Drafts such as IEEE 3218 and ISO TC 307/322 detail methodology for technical interfaces, security, data models, and payment/identity protocols (e.g., ISO 14065 for GHG project accreditation, ISO 20022 for payments).

All major initiatives converge on minimum requirements such as cryptographically unique credit IDs, public metadata, MRV provenance commitments, audited retirement, and cross-registry compatibility (Baiz, 2024).

5. Quantitative Effectiveness and Empirical Appraisal

Systematic review and meta-analysis evidence indicates that the effective decarbonization impact of VCMs is weak relative to compliance mechanisms (Salguero, 7 Dec 2025):

Instrument Type	Offset Achievement Ratio (OAR)	Typical Realized Impact
Carbon Taxes / ETS	N/A	–6.8% to –10.4% emissions reduction (CI adjusted)
VCM Offsets	<16%	≤ –1.6% of claimed credits; OAR by type: REDD+ ≈25%, Wind ≈0%

Most project types suffer extreme over-issuance—ratios up to 1:13 documented in REDD+ portfolios (13 credits per real ton reduced) (Salguero, 7 Dec 2025). By contrast, well-designed compliance mechanisms demonstrate moderate, statistically significant reductions in GHGs across sectors and geographies.

6. Market Design, User Perception, and Trust

Evidence from interface design experiments establishes that trust in carbon offset claims is driven by access to domain-relevant quantitative data—especially forest-impact metrics and transparent cost breakdowns—at the right level of detail (Guzij et al., 2022). Visual design and imagery are insufficient on their own to foster user trust. Actionable design guidelines recommend:

• Prominently presenting hectares protected, number of trees planted, and annual tCO₂ offset.
• Providing detailed, drill-down cost structure visualizations.
• Delivering machine-readable export of project data for third-party verification.
• Avoiding information overload by matching detail to primary audience.

Real-time, publicly verifiable MRV data and blockchain-anchored registry records further improve trust, though vigilance is needed to prevent “dark patterns” and maintain ecological validity in user experience (Guzij et al., 2022).

7. Recommendations and Future Directions

Empirical evidence and technical reviews converge on the necessity for radical reform to redeem VCMs as credible contributors to global decarbonization (Salguero, 7 Dec 2025, Jaffer et al., 2024, Baiz, 2024). Recommendations include:

• Abandoning offset neutrality narratives in favor of “contribution marking” where credits document co-benefits without overstating climate equivalence.
• Restricting eligibility to ex-post, high-fidelity removals (e.g., geological storage) over counterfactual-based avoided emissions.
• Enforcing unique, government-regulated retirement to preclude double counting and serial transgressions.
• Mandating peer-reviewed, annually updated additionality and baseline tests.
• Implementing risk-calibrated buffer pools and standardized Social-Safeguard/FPIC protocols.
• Integrating automated, open-source dMRV and on-chain oracles to guarantee auditability.
• Fostering interoperability through adoption of shared data schemas and meta-registry layers.
• Recognizing that system integrity is gated by the weakest link in the MRV-to-retirement sequence; thus, reforms must span technical, registry, and governance domains holistically.

In their current state, VCMs are not reliable climate solutions and may undermine the credibility of net-zero targets unless such reforms are rigorously implemented (Salguero, 7 Dec 2025).