Carbon Solutions & Carbon Credits, Explained
Everything from "what is a carbon credit" to how to judge whether one is any good — written for buyers, students, journalists, and the curious.
What is a carbon credit?
A carbon credit is a tradable certificate representing one metric tonne of carbon dioxide (or its equivalent in other greenhouse gases, "CO₂e") that has been avoided, reduced, or removed from the atmosphere by a specific project. A company or individual can buy a credit and "retire" it — permanently taking it out of circulation — to claim that tonne against their own emissions.
Credits are not a permit to pollute and they are not a regulatory requirement in most of the world; in the voluntary carbon market (VCM), buying them is optional and reputational. In compliance markets — the EU Emissions Trading System, California's Cap-and-Trade program, and similar schemes — governments require certain industries to hold allowances or offsets, and trading is legally mandated.
Voluntary Carbon Market (VCM)
Companies, events, and individuals buy credits by choice, usually to back a net-zero pledge or offset a specific activity (a flight, a conference, a product's footprint). Quality varies enormously because there is no single global regulator — which is exactly why independent standards and rating agencies (covered on our Rating Institutes page) matter so much here.
Compliance Carbon Market
Government-mandated cap-and-trade or carbon-tax systems where regulated entities must surrender allowances or eligible offsets to cover their emissions. Examples include the EU ETS, California's program (which recognizes credits from the American Carbon Registry and Climate Action Reserve), and the UK ETS. Rules, eligible project types, and prices are set by regulation, not by buyer preference.
Additionality, permanence, and leakage
Almost every controversy over "junk carbon credits" traces back to one of these three concepts. Understand them and you can ask sharper questions about any project.
Would this have happened anyway?
A credit should only represent emissions reductions that would not have occurred without the carbon finance. If a forest was never going to be logged anyway, "protecting" it isn't additional. Additionality is the single most disputed and hardest-to-verify concept in the market.
Will the carbon stay stored?
A tree that sequesters carbon for 20 years and then burns in a wildfire hasn't delivered a permanent reduction. Geological storage and biochar can lock away carbon for centuries; some nature-based projects carry real reversal risk, which is why buffer pools and insurance mechanisms exist.
Did the problem just move?
If protecting one forest simply pushes loggers to clear the forest next door, the net global emissions impact is zero even though the project "worked" locally. Rigorous methodologies model and discount for leakage; weak ones ignore it.
Where do carbon credits actually come from?
"Carbon credit" describes the certificate, not the underlying activity. Here are the major project categories you'll encounter, roughly ordered from lowest to highest typical durability.
🌲 Forestry & land use (REDD+, afforestation, IFM)
The largest category by volume. Includes avoided deforestation (REDD+), planting new forest (afforestation/reforestation), and improved forest management (IFM). High co-benefits for biodiversity, but historically the category most exposed to additionality and permanence criticism — which is why independent ratings and 2024–26 methodology overhauls at Verra and the ICVCM have focused here first.
🌾 Soil carbon & regenerative agriculture
Practices like no-till farming, cover cropping, and managed grazing increase carbon stored in soil. Measurement is improving fast (remote sensing plus soil sampling), but soil carbon can be re-released quickly if practices lapse, so permanence monitoring matters more here than almost anywhere else.
🌊 Blue carbon (mangroves, seagrass, wetlands)
Coastal ecosystems sequester carbon at rates several times higher per acre than most forests, plus deliver storm protection and fisheries benefits. Still a small share of the market but growing quickly as measurement science matures.
🔥 Biochar
Biomass is heated without oxygen (pyrolysis) into a stable charcoal-like substance that locks carbon away for 100+ years when added to soil. One of the highest-confidence durable-removal categories, certified in detail by standards like Puro.earth.
🏭 Direct air capture & geological storage
Engineered technology pulls CO₂ directly from the air (or captures it at an industrial source) and injects it into deep geological formations for storage measured in centuries to millennia. Extremely durable and easy to measure, but currently the most expensive credit type per tonne.
⚡ Renewable energy & avoided emissions
Older-generation credits from wind, solar, and efficiency projects that avoid future emissions rather than removing existing CO₂. Additionality is now widely questioned for renewables in markets where clean energy is already cost-competitive, and most major buyers have shifted away from this category since the early 2020s.
Two very different promises, sold under the same word
Emissions avoidance / reduction credits
These prevent a tonne of CO₂ that would otherwise have entered the atmosphere (e.g., a cookstove project that avoids burning wood, or a wind farm displacing coal power). They do not remove any existing atmospheric carbon.
Carbon removal credits
These represent carbon actively pulled out of the atmosphere and stored — forestry sequestration, biochar, soil carbon, direct air capture. Corporate net-zero standards (like the Science Based Targets initiative) increasingly require removals, not just avoidance, to count toward long-term "neutral" claims.
From project design to your retirement certificate
Project design
A developer designs a project against a published methodology (e.g., a specific REDD+ or biochar methodology) from a registry such as Verra or Gold Standard, establishing a baseline for what would have happened without the project.
Validation
An accredited third-party auditor checks the project design against the methodology before it starts issuing credits.
Monitoring & verification
Once running, the project is monitored (satellite data, field measurement, sensors) and periodically re-audited to confirm real-world performance matches the claim.
Issuance
The registry issues serialized credits into a public registry ledger — one credit per verified tonne.
Independent rating (optional but recommended)
Agencies like BeZero Carbon, Sylvera, and Calyx Global assess credit quality independently of the registry and publish a letter-grade rating buyers can check before purchasing.
Trade & retirement
A buyer purchases the credit, then "retires" it in the registry — permanently removing it from circulation so it can never be resold or claimed twice.
Straight answers to common questions
Are carbon credits a scam?
Not inherently — but the market has real quality problems, particularly in older forestry methodologies, and several journalistic investigations (2023–2025) found some widely-used projects delivered far less benefit than claimed. The fix isn't avoiding credits altogether; it's using independent ratings, buying CCP-labelled or high-rated credits, and favoring durable removal categories when the goal is a genuine offset claim.
What's the difference between a "registry" and a "rating agency"?
A registry (Verra, Gold Standard, ACR, CAR, Puro.earth) writes the rulebook, approves projects, and issues the credits. A rating agency (BeZero, Sylvera, Calyx Global) is an independent reviewer that grades how good a specific project's credits actually are, similar to how a bond rating agency grades a bond after it's issued. See our full Rating Institutes directory.
What does "CCP-Approved" mean?
It means a methodology has passed assessment against the Integrity Council for the Voluntary Carbon Market's (ICVCM) Core Carbon Principles — a baseline threshold for credible carbon credits. Not all methodologies from major registries have been assessed yet, and assessment is ongoing category by category (forestry, renewable energy, household devices, and more).
Should my company buy carbon credits at all?
Most credible frameworks (including the Science Based Targets initiative) now recommend a "mitigation hierarchy": first measure your footprint, then reduce your own emissions as much as possible, and only use credits — ideally durable removals — for the residual emissions you cannot yet eliminate. Credits are not a substitute for decarbonizing your own operations.
What is a "vintage"?
The vintage is the year the underlying emission reduction or removal actually occurred (not the year the credit was issued or sold). Older vintages sometimes trade at a discount because buyers prefer recent, verifiable activity.
Want the full A–Z reference?
Our glossary defines every term used on this page — and dozens more — in one scrollable reference.