"Carbon credit" describes two very different things. In the voluntary market, certifiers like the Washington-based Verra and Geneva-based Gold Standard issue project-based offsets to companies wanting to call a product "carbon neutral." In the compliance market, governments run cap-and-trade systems that force polluters to pay — and the largest, the EU's, does not use offsets at all. Both the scandal that gutted confidence in carbon credits and the blockchain projects built to repair it sit on the voluntary side; the regulation now reshaping the field comes from the compliance side.
Key Points
- A 2023 investigation found the large majority of one major certifier's rainforest credits likely delivered no real cuts; the research later cleared peer review in Science.
- Voluntary-market volume fell by more than half in 2023 as buyers fled greenwashing risk.
- Europe's mandatory market never ran on offsets, and from September 2026 EU law bans offset-based "carbon neutral" product claims — squeezing the very market blockchain set out to rescue.
When A Tonne Stopped Meaning A Tonne
In January 2023, a joint investigation by the Guardian, Die Zeit and SourceMaterial concluded that upward of 90% of Verra's rainforest offsets — credits from the certifier behind most of the voluntary market — were likely worthless. Verra disputed the methodology, but its long-serving chief executive left within months, and the underlying research was later peer-reviewed in Science. A separate meta-analysis of almost a billion tonnes of credits, close to a fifth of all volume ever issued, found fewer than one in six reflected a genuine reduction.
Buyers walked: voluntary-market volume fell roughly 56% in 2023, on Ecosystem Marketplace's numbers, as the reputational risk of a bad offset came to outweigh the value of a good one. Underneath sat a counting problem — the same tonne claimed at once by developer, registry and host country — which COP29 tried to close in 2024 with the Article 6 "corresponding adjustments" rulebook.
Europe Took A Different Road
Europe barely uses offsets. The EU Emissions Trading System, the world's oldest and most valuable mandatory carbon market, caps emissions from roughly 10,000 installations plus aviation and shipping, issues one tradeable allowance per tonne, and shrinks that cap toward zero around 2039; an allowance costs near €70 in 2026. The system once accepted international project credits, but those were phased out — a Verra credit cannot meet a European obligation, and the registry tracking it all is a government database, not a blockchain. That is largely why the on-chain experiments stayed in the voluntary market.
Europe is closing the softer route too. From 27 September 2026, Directive (EU) 2024/825 bans labelling a product "carbon neutral" when the claim rests on offsetting outside its value chain, with penalties up to 4% of turnover; German courts have enforced the same logic since 2024. Offsets can still be bought — just no longer worn as a marketing badge.
Crypto Tried First, And Made It Worse
The first on-chain attempt enlarged the quality problem rather than solving it. Toucan launched in October 2021 with a bridge — retire a Verra credit, mint a tradeable Base Carbon Tonne in its place — and moved around 22 million credits on-chain within months. KlimaDAO stacked a high-yield treasury on top, creating a strong incentive to bridge as much volume as fast as possible.
The flaw was what that pulled in. The bridge's bar was deliberately low, so the cheapest credits moved first: a CarbonPlan study found nearly all bridged credits came from projects excluded by the strictest quality benchmarks, including "zombie" projects revived only because tokenising them had become profitable. Worse, pooling credits of different vintages and types into one fungible token erased the project-level detail that separates a real reduction from a worthless one. The chain wasn't filtering bad credits out — it was making them more liquid and lending them an air of precision. In May 2022 Verra banned tokenising retired credits, cutting off supply; Base Carbon Tonnes slid from roughly $8 to $2 as crypto speculation drained away. Tellingly, when Verra later sought a digital path of its own, it backed a bank-run network, Carbonplace, over any public chain.
Where Yellow Network Fits
This is the gap Yellow Network aims at — not as a registry replacement. Yellow runs on state channels: signed agreements that parties update privately, settling to a public chain only when a permanent record is needed. Mapped onto carbon, a developer signs its measurement data, an accredited verifier counter-signs, and only then is a credit minted with that signed provenance attached — kept as a distinct, traceable instrument rather than dissolved into an anonymous pool, the flaw that undid the first wave. Retirement is a co-signed, irreversible burn, so a credit can't be sold twice.
But the ceiling is real, and it is the one regulators are circling. A ledger can prove a credit hasn't been altered or resold since issuance; it cannot vouch for the honesty of the first measurement. Inflate a forest's baseline — as the Guardian's analysis of a 2022 Cambridge study estimated some Verra projects effectively did, by around fourfold — and that figure, once signed, travels downstream looking flawless. The rot lived in the methodology, upstream of anything a blockchain sees. The EU's answer to that is accreditation, not cryptography: its new Carbon Removal Certification Framework tries to define what a real removal is before anyone is allowed to count it.
What Would Actually Count As Fixed
So — can blockchain fix carbon credits? Not alone, and not in the 2021 form where a token routes around the registries and stands in for trust never earned upstream. In Europe that version was a non-starter anyway. The one with a future is narrower: accredited bodies keep doing the judgement work, while a shared ledger beneath them makes whatever credits survive harder to double-count, forge or quietly edit. The hard part isn't technical — it is getting registries, verifiers, regulators and buyers to agree on a system worth settling on. Manage that, and the credits that emerge will at least be ones a buyer can independently check.