Compliance vs Voluntary Markets
Carbon markets are not monolithic. The term covers a spectrum of instruments ranging from legally mandated compliance systems governed by national or supranational law, to entirely voluntary schemes driven by corporate commitments and reputational incentives. Understanding where voluntary carbon markets sit within this landscape, and how they interact with compliance systems, is essential context for anyone working in climate finance.
Compliance Markets: Participation Is Required
In a compliance carbon market, regulated entities must surrender allowances or credits equal to their emissions at the end of each compliance period, or face penalties. Participation is not optional. The world's major compliance systems include:
- EU Emissions Trading System (EU ETS): The world's oldest and largest cap-and-trade system, launched in 2005 and covering roughly 40% of EU greenhouse gas emissions. Power generators, large industrial plants, and intra-EU aviation must surrender EU Allowances (EUAs). The EUA price exceeded €100 per tonne in 2023 before retreating amid energy market volatility.
- California-Quebec Cap-and-Trade: A linked system covering large emitters in California and Quebec. Carbon allowances (CCAs) are auctioned quarterly; the system covers approximately 85% of California's statewide GHG emissions.
- China National ETS: Launched in 2021, covering the power sector and making China's ETS the world's largest by covered emissions, approximately 4 billion tonnes of CO2 per year.
- CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation): A baseline-and-offset scheme administered by ICAO requiring international airlines to offset emissions above 2019 baseline levels from 2024 onward. CORSIA accepts a defined list of eligible offset programs, including Verra VCS and Gold Standard.
Compliance Credits vs Voluntary Credits
In most compliance systems, regulated entities primarily surrender government-issued allowances. However, many compliance programs allow a limited proportion of compliance obligations to be met using project-based offset credits, including some VCS and Gold Standard credits. When a voluntary credit is used in a compliance context, additional requirements (such as corresponding adjustments under Article 6 of the Paris Agreement) may apply.
Article 6 of the Paris Agreement: The International Linkage
The Paris Agreement, adopted in 2015, introduced a new architecture for international carbon markets through Article 6. Article 6.2 allows countries to transfer "Internationally Transferred Mitigation Outcomes" (ITMOs) bilaterally, enabling one country to count emission reductions achieved in another country toward its own Nationally Determined Contribution (NDC). Article 6.4 establishes a new UN-supervised crediting mechanism intended as a successor to the Kyoto Protocol's Clean Development Mechanism.
Article 6 is significant for voluntary markets for two reasons. First, it introduces the concept of "corresponding adjustments": when a carbon credit is used by a buyer in one country toward a climate target, the host country where the emission reduction occurred must make an equivalent upward adjustment to its own emissions accounting, so the reduction is not counted twice. Second, CORSIA and some national compliance systems are beginning to require corresponding adjustments for credits they accept, potentially affecting demand for and pricing of voluntary credits.
The Scorecard Analogy
Imagine two countries, each keeping a carbon scorecard. Country A finances a wind farm in Country B, reducing Country B's emissions by 100 tonnes. If Country A claims those 100 tonnes toward its Paris pledge, Country B must add 100 tonnes back onto its own scorecard (a corresponding adjustment), so the global tally still reflects only one real reduction. Without this rule, the same tonne could be counted by both countries, creating a double-counting loophole.
Voluntary Markets: Participation Is by Choice
Voluntary carbon markets (VCMs) operate entirely outside mandatory compliance frameworks. Companies, organisations, and individuals purchase carbon credits because they have made voluntary commitments to achieve net zero, carbon neutrality, or other climate goals, not because the law requires it. The motivations are varied: reputational management, alignment with science-based targets, stakeholder expectations, anticipation of future regulation, and genuine conviction about corporate responsibility.
Because participation is voluntary, the VCM lacks the coercive force of a compliance regime. Quality control must instead come through market norms, standards, and reputational incentives. This is precisely the role played by standard-setting bodies like Verra and Gold Standard, and more recently by integrity frameworks like the Integrity Council for the Voluntary Carbon Market (ICVCM) and the Voluntary Carbon Markets Integrity Initiative (VCMI).
| Feature | Compliance Markets | Voluntary Markets |
|---|---|---|
| Participation | Mandatory for regulated entities | Voluntary, driven by corporate commitments |
| Primary instrument | Government allowances (sometimes + offsets) | Project-based offset credits |
| Price discovery | Auction or exchange | Bilateral OTC, brokers, exchanges |
| Oversight | Regulatory authority (government) | Standards bodies + market integrity initiatives |
| Credit quality benchmark | Defined by regulation | Core Carbon Principles (ICVCM), program rules |
| Double-counting rules | Strict (embedded in law) | Evolving (Article 6 alignment in progress) |
How VCMs Complement Rather Than Compete
A common misconception is that voluntary markets undermine compliance systems by allowing companies to avoid real reductions. The ICVCM's Assessment Framework emphasises that high-integrity voluntary credits represent genuine emission reductions or removals that would not have occurred without carbon market finance. Used correctly within a mitigation hierarchy where companies reduce their own emissions first, and use credits only for residual or hard-to-abate emissions, voluntary markets direct investment to solutions that compliance systems cannot efficiently reach: community cookstove projects in Sub-Saharan Africa, peatland restoration in Southeast Asia, and regenerative agriculture across smallholder landscapes.
The boundary between compliance and voluntary is also blurring. CORSIA accepts voluntary registry credits for airline compliance. Several national ETS programs allow offset credits from voluntary registries. As Article 6 rules mature, voluntary credits with corresponding adjustments may become a new category of "high-integrity" instrument straddling both markets.
Key Takeaways
- 1Compliance markets require regulated entities to surrender allowances or offsets by law; voluntary markets are driven by corporate climate commitments and are entirely optional
- 2Major compliance systems include the EU ETS, California-Quebec Cap-and-Trade, China's national ETS, and CORSIA for international aviation
- 3Article 6 of the Paris Agreement introduces corresponding adjustments to prevent double-counting, a concept increasingly relevant to voluntary market credits
- 4High-integrity voluntary credits complement compliance systems by directing finance to emission reductions and removals that mandatory schemes cannot efficiently reach