In December 2023, something unusual happened in the voluntary carbon market. Across the four major registries — Verra, Gold Standard, ACR, and CAR — a record 31.36 million credits were retired in a single month. Year-end surges are normal. This one was not.
The number that should stop you: among identified offset buyers, Shell alone accounted for 58.6% of all retirements. The oil and gas sector as a whole reached 61.1%. The second-largest buyer was Audi, placing the automotive sector at 11.6%. The voluntary carbon market's biggest customers are, by a wide margin, the world's largest emitters.
Sizing the structural gap
To understand what this concentration means, you need the full picture of carbon pricing. According to the World Bank Carbon Pricing Dashboard, direct carbon pricing instruments — emissions trading systems plus carbon taxes — generated $102.2 billion in government revenue in 2024. Of that, ETS auctions contributed roughly $69.1 billion, carbon taxes $33.1 billion.
The voluntary carbon market, by contrast, transacts an estimated $1–2 billion annually. That is roughly one-hundredth of the compliance market. Yet the VCM receives disproportionate attention in policy debates and ESG investment circles. The reason is straightforward: this is where corporate climate commitments reveal their true nature.
Three structural risks from oligopoly
Concentration is occurring on both the demand side and the supply side simultaneously, creating compounding fragility.
Demand-side: oil major dependency
Shell announced the cancellation of its $100 million annual carbon offset investment plan in September 2023. Yet December data showed the company remained the market's largest buyer by a commanding margin. If Shell genuinely exits, the market contracts substantially. If Shell shifts purchasing preferences, entire credit categories rise or fall. A single corporate treasury decision reshapes the market.
This is the opposite of what carbon pricing is supposed to achieve. The design intent — distributed incentives driving broad-based emissions reduction — has been inverted into a structure where a handful of major emitters determine market dynamics.
Supply-side: the Verra monopoly
On the supply side, Verra's Climate, Community & Biodiversity (CCB) programme accounted for 52.3% of December retirements. By methodology, REDD+ (avoided deforestation) held approximately 40% market share, with renewable energy credits at 21%. Registry competition is not functioning.
The quality mismatch
63.8% of retired credits were classified as providing "additional social benefits." Yet at the methodology level, REDD+ — an avoidance-based approach with well-documented integrity concerns — held the largest share. The gap between marketing claims and underlying methodology is material.
What is underpriced
The conventional framing asks whether the VCM will grow. The more important question is whether its current structure can survive a single buyer's change of heart.
Business models dependent on VCM revenue — project developers, intermediaries, carbon tech platforms — carry concentrated counterparty risk to a handful of fossil fuel companies' purchasing decisions. This is not a market risk. It is a structural dependency.
The compliance market tells a different story. Its infrastructure — MRV technology, registry interoperability, digital verification — has policy backing and institutional momentum. Growth there is driven by regulation, not by voluntary corporate strategy that can reverse in a quarter.
The real risk in carbon credit markets is not the size of the voluntary market. It is the structural concentration that makes the entire ecosystem dependent on the purchasing decisions of the companies it was meant to constrain.
The path forward: quality as market architecture
As the Paris Agreement's Article 6 mechanisms become operational, the boundary between voluntary and compliance markets will blur. The critical variable is whether quality standards — particularly the ICVCM Core Carbon Principles — gain enough traction to restructure buyer behavior and registry competition.
If quality becomes visible and verifiable, buyer diversification follows. If it does not, the oligopoly paradox persists: the market designed to price externalities remains priced by the externality producers themselves.