Case study: Voluntary carbon market integrity (ICVCM, VCMI) — a city or utility pilot and the results so far

The City of Seattle became one of the first US municipalities to formally align its carbon offset procurement with the Integrity Council for the Voluntary Carbon Market's (ICVCM) Core Carbon Principles (CCPs) in 2024, requiring that all credits purchased through its municipal climate programs carry CCP-approved labels. By early 2026, the city has retired 185,000 CCP-labeled credits across its municipal operations, transit electrification gap-filling, and community resilience programs, while simultaneously adopting the Voluntary Carbon Markets Integrity Initiative's (VCMI) Claims Code of Practice for its public-facing emissions reduction communications (City of Seattle Office of Sustainability, 2025). This case study examines how Seattle designed, implemented, and measured a city-level voluntary carbon market integrity framework that other municipalities and utilities are now studying as a replicable model.

Why It Matters

The voluntary carbon market transacted approximately $1.7 billion in 2024, down from a peak of $2 billion in 2022, as buyers paused purchases amid concerns over credit quality and greenwashing accusations (Ecosystem Marketplace, 2025). High-profile investigations into forest offset reversals, inflated baselines, and additionality failures eroded institutional trust. A 2024 analysis by the Berkeley Carbon Trading Project found that roughly 40% of forestry credits issued between 2015 and 2022 by major registries were associated with overestimated emissions reductions. For municipalities and utilities that rely on offsets to address residual emissions in their climate action plans, this integrity crisis is not abstract: it directly undermines the credibility of public decarbonization commitments and exposes procurement officers to reputational and regulatory risk.

The ICVCM's Core Carbon Principles, finalized in March 2023 and operationalized through the CCP Assessment Framework in July 2024, established the first global benchmark for credit quality. Credits earning CCP labels must demonstrate additionality, permanence, robust quantification, and alignment with sustainable development goals. The VCMI Claims Code, launched in June 2023 with its final version in November 2024, provides a framework for organizations to make credible claims about their use of carbon credits, distinguishing between "Gold," "Silver," and "Bronze" tiers based on the rigor of the buyer's underlying decarbonization trajectory. Together, these two frameworks create an end-to-end integrity system: ICVCM governs supply-side credit quality, and VCMI governs demand-side buyer credibility.

For executives managing municipal or utility climate budgets, the operational question is whether aligning procurement to these new frameworks improves outcomes or simply adds compliance cost. Seattle's pilot offers concrete data on both sides of that equation.

Key Concepts

Understanding Seattle's approach requires familiarity with several concepts that underpin voluntary carbon market integrity.

Core Carbon Principles (CCPs) are ten criteria established by the ICVCM that a carbon credit methodology or program must satisfy to receive a CCP label. These include additionality (the emission reduction would not have occurred without carbon finance), permanence (the reduction is durable and any reversal risk is managed through buffer pools or insurance), robust quantification (baselines and monitoring follow conservative, peer-reviewed methodologies), and contribution to the host country's sustainable development priorities. As of early 2026, nine credit methodologies across four registries have received CCP-eligible status, covering approximately 25% of annual issuance volume.

VCMI Claims Code of Practice defines three tiers of credible climate claims for credit buyers. The Gold tier requires a buyer to have validated science-based targets covering Scope 1, 2, and 3 emissions, demonstrate on-track progress, and retire high-quality credits for residual emissions. Silver and Bronze tiers allow less complete coverage but still require transparent disclosure and a credible decarbonization trajectory. The framework explicitly prohibits claims of "carbon neutrality" based on offsets alone.

Municipal carbon procurement refers to the process by which city governments purchase carbon credits to address emissions that cannot be eliminated through direct operational changes. Seattle's municipal operations produce approximately 320,000 metric tons of CO2 equivalent annually, of which roughly 58% has been addressed through efficiency upgrades, fleet electrification, and renewable energy procurement, leaving a residual gap that the city addresses through credit retirement.

Credit vintage and traceability describes the year in which an emission reduction occurred and the chain of custody documentation linking a credit from issuance through retirement. Seattle's policy requires that retired credits carry vintages no older than three years and include registry-verified traceability records.

What's Working

Credit Quality Has Measurably Improved

Before adopting CCP alignment, Seattle's offset portfolio drew from 14 different project types across three registries with no standardized quality screen beyond registry listing. An internal audit conducted in 2023 found that 31% of previously retired credits came from methodologies that would not satisfy CCP additionality requirements, primarily large-scale renewable energy projects in countries where renewables were already economically competitive without carbon finance. Under the new procurement framework, 100% of credits retired since July 2024 carry CCP-eligible labels. The portfolio now concentrates on cookstove distribution, methane avoidance from waste management, and direct air capture removal credits, all of which passed ICVCM's Assessment Framework (City of Seattle Office of Sustainability, 2025).

Price Premium Is Lower Than Expected

Market analysis projected that CCP-labeled credits would command a 40 to 60% premium over unlabeled credits. Seattle's actual procurement data shows a more modest differential. The city paid an average of $14.20 per ton for CCP-labeled avoidance credits in 2025, compared to $10.80 per ton for its pre-CCP portfolio average in 2023. For removal credits, which the city began purchasing in Q3 2024, the average price was $85 per ton for biochar-based removals and $340 per ton for a small allocation of direct air capture credits. The blended portfolio cost of $22.50 per ton, with removals representing 12% of volume, remained within the city's climate action plan budget of $4.2 million annually. The premium exists but has not been budget-breaking at current volumes (Ecosystem Marketplace, 2025).

Public Trust Metrics Have Shifted

Seattle's Office of Sustainability conducts biannual public surveys on trust in municipal climate programs. The 2025 survey, conducted six months after the city adopted the VCMI Claims Code for its public communications, showed a 14-percentage-point increase in residents who rate the city's climate claims as "credible" or "very credible," rising from 41% to 55%. The survey also found that awareness of carbon market integrity frameworks among respondents increased from 8% to 23%, suggesting that the city's transparent reporting is contributing to broader public literacy on offset quality. The survey drew 3,200 responses across all council districts, with confidence intervals of plus or minus 2.5 percentage points (City of Seattle, 2025).

Utility Partner Adoption Is Accelerating

Seattle City Light, the municipally owned electric utility, aligned its own voluntary renewable energy credit and carbon offset procurement with the CCP framework in January 2025. Puget Sound Energy, the investor-owned utility serving adjacent King County, followed suit in Q3 2025 after observing Seattle City Light's implementation. Together, the two utilities now represent approximately 2.8 million customer accounts purchasing CCP-aligned credits. Puget Sound Energy reported that alignment with CCP criteria simplified its internal credit approval process by reducing the number of due diligence reviews per procurement cycle from 12 to 4, because CCP labeling pre-screens for the quality indicators that had previously required case-by-case assessment (Puget Sound Energy, 2025).

What's Not Working

Supply Constraints Limit Portfolio Diversification

Only nine methodologies had received CCP-eligible status by early 2026, covering roughly 25% of total annual credit issuance. This means Seattle's procurement team has a much narrower pool of projects to source from. Nature-based solutions, which represented 60% of the city's pre-CCP portfolio, are underrepresented in current CCP-eligible supply because several forestry and land-use methodologies remain under ICVCM review. The city's 2025 procurement cycle saw three competitive solicitations where only two bidders submitted CCP-compliant proposals, down from an average of seven bidders under the previous open procurement approach. The reduced competition risks both higher prices and concentration risk in the portfolio.

Small Project Developers Are Disadvantaged

The CCP assessment process requires significant documentation, third-party validation, and ongoing monitoring that impose fixed costs disproportionately burdensome for small-scale project developers. Community-level cookstove programs, smallholder agroforestry projects, and municipal waste-to-energy initiatives in developing countries often lack the resources to navigate the CCP application process. Seattle's procurement officers have noted that the CCP pipeline skews toward larger, well-capitalized project developers, potentially undermining the sustainable development co-benefits that motivated the city's offset program in the first place. A 2025 ICVCM review acknowledged this concern and announced a simplified assessment pathway for projects below 10,000 tons per year, but the pathway was not yet operational as of Q1 2026.

VCMI Claims Code Adoption Remains Voluntary

While Seattle has adopted the VCMI Claims Code for its public communications, the framework has no enforcement mechanism. Neighboring jurisdictions and private-sector buyers can make climate claims without any reference to the Claims Code, creating an uneven playing field. Seattle's communications team reported confusion among stakeholders about why the city restricts its language to "contribution claims" under the VCMI framework while other regional entities continue to use "carbon neutral" labeling without comparable rigor. The absence of regulatory teeth behind the Claims Code means that early adopters bear compliance costs while laggards face no penalty.

Measurement of Additionality Remains Contested

Even within CCP-eligible methodologies, determining whether an emission reduction is truly "additional" involves counterfactual reasoning that is inherently uncertain. Seattle's procurement review board flagged two approved cookstove projects where baseline assumptions about fuel-switching rates appeared optimistic based on updated survey data from the host countries. The ICVCM's Assessment Framework provides standardized rules, but those rules still require judgment calls about baseline scenarios that can be contested in good faith. The city added an internal additionality review step that examines host country energy transition trends, adding 6 to 8 weeks to the procurement timeline.

Key Players

Established Organizations

• Integrity Council for the Voluntary Carbon Market (ICVCM): Developed and administers the Core Carbon Principles and CCP Assessment Framework that form the quality benchmark for Seattle's procurement policy.
• Voluntary Carbon Markets Integrity Initiative (VCMI): Created the Claims Code of Practice that Seattle uses to govern its public-facing climate communications and claims.
• Verra: The largest carbon credit registry by issuance volume, with several methodologies undergoing CCP assessment. Verra's VCS program issued approximately 280 million credits in 2024.
• Gold Standard: A registry with a strong sustainable development focus, which had three methodologies receive CCP-eligible status as of early 2026.
• Seattle City Light: The municipally owned utility that adopted CCP-aligned procurement for its voluntary offset purchases, covering 460,000 customer accounts.

Startups

• Sylvera: Provides AI-driven carbon credit ratings and due diligence tools that Seattle's procurement team uses to screen CCP-eligible credits for project-level performance.
• BeZero Carbon: Offers independent credit ratings on a AAA-to-D scale, supplementing registry-level CCP labels with project-specific risk assessments used in Seattle's portfolio construction.
• Pachama: Uses satellite imagery and machine learning to monitor forest carbon projects, providing the remote verification data that supports permanence assessments under the CCP framework.

Investors and Funders

• Bezos Earth Fund: Provided $20 million in funding to the ICVCM to support development and operationalization of the Core Carbon Principles framework.
• Bloomberg Philanthropies: Funded VCMI's Claims Code development and supports municipal adoption programs, including technical assistance for cities implementing the framework.
• Rockefeller Foundation: Co-funded the Energy Alliance initiative that supports developing-country project developers in navigating CCP assessment requirements.

KPI Summary

KPI	Baseline (2023)	Current (2025)	Target (2028)
CCP-labeled credits retired (annual)	0	185,000	320,000
Portfolio credit quality (% CCP-aligned)	0%	100%	100%
Average avoidance credit cost ($/ton)	$10.80	$14.20	$12.00
Public trust in climate claims (% credible)	41%	55%	70%
Removal credits as % of portfolio	0%	12%	30%
Utility partners aligned with CCP	0	2	6
Procurement cycle duration (weeks)	8	14	10

Action Checklist

• Conduct an internal audit of current carbon credit portfolios to assess what percentage of retired credits would satisfy ICVCM Core Carbon Principles criteria
• Establish procurement policies requiring CCP-labeled credits for all future offset purchases, with phase-in timelines aligned to CCP-eligible supply availability
• Adopt the VCMI Claims Code of Practice for all public-facing climate communications to ensure credible, defensible language around offset use
• Engage with registries (Verra, Gold Standard, ACR, CAR) to understand which methodologies are CCP-eligible and build procurement pipelines accordingly
• Integrate third-party credit rating tools from providers like Sylvera or BeZero Carbon into due diligence workflows to supplement CCP labels with project-level risk data
• Allocate a portion of the offset budget (10 to 20%) to carbon removal credits to build procurement experience and signal demand for high-permanence solutions
• Advocate through municipal networks (C40, ICLEI) for regulatory recognition of the VCMI Claims Code to create a level playing field for early adopters

FAQ

Q: What is the difference between ICVCM and VCMI? A: The ICVCM governs supply-side credit quality through its Core Carbon Principles, which set standards for what makes a carbon credit high-integrity. It evaluates methodologies and programs used by registries to issue credits, and labels qualifying credits as CCP-eligible. The VCMI governs demand-side buyer behavior through its Claims Code of Practice, which defines how organizations can make credible public claims about their use of carbon credits. In practice, the two frameworks are complementary: ICVCM ensures you are buying good credits, and VCMI ensures you are communicating about them honestly. A municipality like Seattle uses both, requiring CCP labels on purchased credits (supply-side) and following the Claims Code for public statements (demand-side).

Q: How much more do CCP-labeled credits cost compared to conventional credits? A: Seattle's procurement data shows CCP-labeled avoidance credits averaging $14.20 per ton in 2025, compared to a pre-CCP portfolio average of $10.80 per ton in 2023, representing a roughly 31% premium. However, this premium reflects both the CCP quality screen and general market price recovery from 2023 lows. Industry analysts expect the premium to narrow as more methodologies receive CCP eligibility and supply expands. For removal credits, prices range from $85 per ton for biochar to over $300 per ton for direct air capture, but these price points reflect the cost of the underlying technology rather than the CCP label itself. The blended portfolio cost depends heavily on the ratio of avoidance to removal credits.

Q: Can smaller cities replicate Seattle's approach without a dedicated sustainability office? A: The core elements of Seattle's framework, requiring CCP-labeled credits and adopting VCMI Claims Code language, are administrative rather than technical and can be embedded in existing procurement policies without dedicated staff. Several mid-size cities, including Boise, Idaho, and Madison, Wisconsin, have incorporated CCP requirements into their general procurement guidelines using template language developed by ICLEI. However, the more sophisticated elements, such as internal additionality review, portfolio construction with removal credit allocations, and public trust measurement, do require staff capacity. Cities with limited resources can start with the procurement policy alignment and expand to communications and monitoring as capacity develops.

Q: What risks does a city face if it does not adopt integrity frameworks? A: The primary risks are reputational and regulatory. Municipalities that continue purchasing low-quality credits face growing scrutiny from local media, environmental advocacy groups, and residents who are increasingly aware of greenwashing concerns. The EU's Green Claims Directive, expected to take effect in 2026, will prohibit unsubstantiated environmental claims by organizations operating in European markets, and similar regulatory proposals are advancing in California and New York. Cities that have not aligned with recognized integrity frameworks may find their climate claims challenged in administrative or legal proceedings. Additionally, credits from non-CCP methodologies may face declining market value as institutional buyers consolidate purchasing around CCP-eligible supply, creating stranded asset risk for credits already held in municipal portfolios.

Sources

• City of Seattle Office of Sustainability. (2025). Municipal Carbon Procurement Policy: Year One Implementation Report. Seattle, WA: City of Seattle.
• Ecosystem Marketplace. (2025). State of the Voluntary Carbon Market 2025: Market Size, Trends, and Integrity Developments. Washington, DC: Forest Trends.
• Integrity Council for the Voluntary Carbon Market. (2024). Core Carbon Principles Assessment Framework: Operational Guidance and Methodology Eligibility Status. London, UK: ICVCM.
• Voluntary Carbon Markets Integrity Initiative. (2024). Claims Code of Practice: Final Version and Implementation Guidance. London, UK: VCMI.
• Puget Sound Energy. (2025). Sustainability Report 2024: Carbon Offset Procurement and Quality Alignment. Bellevue, WA: Puget Sound Energy.
• Berkeley Carbon Trading Project. (2024). Voluntary Registry Offsets Database: Analysis of Credit Quality and Overestimation Rates. Berkeley, CA: UC Berkeley.
• City of Seattle. (2025). Biannual Climate Program Public Trust Survey: Methodology and Results. Seattle, WA: City of Seattle.
• Bloomberg Philanthropies. (2025). Municipal Climate Integrity Initiative: Technical Assistance Program Overview. New York, NY: Bloomberg Philanthropies.