A carbon credit represents one metric tonne of carbon dioxide equivalent (tCO₂e) that has been reduced, avoided, or removed from the atmosphere. That sounds simple. The machinery that produces a verified, saleable credit is considerably more complex - and understanding it is the difference between a project that raises finance and one that doesn't.
This guide walks through the full lifecycle of a carbon credit: from the moment a project developer identifies an opportunity, through methodology selection, baseline setting, project design, validation, monitoring, verification, and finally issuance and sale. At each stage, we've embedded the relevant Carbon Workbench tool so you can test the numbers live as you read.
What problem does a carbon credit solve?
Carbon credits exist because most emissions reductions are not commercially viable without additional revenue. A community in rural Kenya can switch from burning firewood to using an efficient cookstove - reducing their emissions - but the fuel savings alone may not cover the cost of the stoves. Carbon credits bridge that gap: they let a company in Europe or the US pay for real emission reductions happening elsewhere, while the project developer earns the revenue needed to make the project financially viable.
The system only works if the credits are credible - if buyers can trust that the claimed tonne was actually reduced or removed, and won't be claimed again. That's what the standards and verification bodies exist to ensure.
The credit lifecycle: seven steps
Identify the opportunity
A project developer identifies an activity that will reduce or remove emissions - cookstove distribution, biochar production, reforestation, solar installation, and so on. The first question is always: does an approved methodology exist for this project type?
Choose a methodology and standard
The methodology is the ruleset that defines how emission reductions are calculated, monitored and verified. The standard body (Gold Standard, Verra, Puro.earth) approves methodologies and maintains the registry. Choosing the wrong one - one that doesn't cover your project type, or that your buyers don't accept - can kill a project years in.
Design the project (PDD)
The Project Design Document (PDD) is the formal description of the project: what it does, where, how it reduces emissions, how the reductions will be measured, and why it qualifies as additional. It's the document that the validation body assesses, and that the standard body uses to decide whether to register the project.
Validation
An accredited Validation and Verification Body (VVB) - an independent auditor approved by the standard - reviews and validates the PDD. They visit the project site, verify the baseline assumptions, check the additionality argument, and confirm the monitoring plan is appropriate. If validation is successful, the project is registered on the standard's registry.
Monitoring
The project developer monitors and documents the project's actual performance during each monitoring period - typically one or two years. For a cookstove project, this means tracking stove distribution, fuel consumption surveys, and usage rates. For biochar, it means testing each batch for H/Corg ratio and carbon content. The monitoring report is what the VVB verifies against.
Verification and credit issuance
The VVB reviews the monitoring report, conducts site visits, and produces a verification report confirming the emission reductions achieved. The standard body uses this to issue credits into the registry - one credit per verified tonne. From this point, credits can be sold.
Sale and retirement
Credits are sold to corporate or individual buyers through brokers, exchanges, or direct agreements. When a buyer uses a credit to offset an emission, it is "retired" - permanently cancelled from the registry so it can never be claimed again. Retirement records are public.
The three concepts that matter most
Additionality
Additionality is the most contested concept in carbon crediting and the source of most controversy about credit quality. Methodologies specify approved additionality tests - most use a combination of a regulatory barrier test (the project isn't required by law), a financial barrier test (it wouldn't be commercially viable without carbon revenue), and a common practice test (similar projects aren't already widespread in the region without carbon support).
The baseline
For a cookstove project, the baseline is the amount of wood the households would have burned using their existing cooking method. For a REDD+ project, the baseline is the rate at which the forest would have been deforested without intervention. Setting the baseline too high inflates credit volumes; setting it accurately is what gives the credit its integrity.
Permanence
This is most relevant for nature-based solutions (forests can burn) and biochar (which can decompose, albeit slowly). Standards address permanence through buffer pools - a percentage of credits held in reserve in case the carbon is later released - or through permanence discounts based on measurable stability indicators like the H/Corg ratio for biochar.
Try the Methodology Selector
The first practical decision for any project developer is choosing the right standard and methodology. This tool maps your project type and priorities to the best-fit options:
Use the full tool in The Carbon Workbench for saved calculations, PDF reports, and access to the wider tool suite once you move beyond a first-pass methodology screen.
Use full tool in The Carbon Workbench →The cost of getting credits to market
Many first-time project developers are surprised by the full cost of verification. A Gold Standard validation can cost £15,000–£25,000 before the first credit is issued. Annual verification adds £8,000–£15,000 per monitoring period on top. For projects generating fewer than 5,000 tCO₂e per year, these fixed costs can consume most of the revenue.
Use the full tool in The Carbon Workbench for saved calculations, PDF reports, and faster switching into feasibility and pricing once the cost picture matters.
Use full tool in The Carbon Workbench →What determines the price of a carbon credit?
Credit prices vary enormously - from under £3/t for older vintage REDD+ credits to over £100/t for high-quality biochar CDR. The main drivers are:
- Standard - Gold Standard commands a premium over Verra VCS; Puro.earth biochar credits trade far above both for removal buyers
- Project type - carbon removal (biochar, DACCS) trades at a premium over carbon avoidance (cookstoves, REDD+), reflecting permanence differences
- Co-benefits - SDG labels, community certification and biodiversity co-benefits add price premium for buyers with impact communications needs
- Vintage - older credits (pre-2016) often trade at a discount; buyers prefer recent vintages
- Additionality quality - projects with stronger additionality arguments command better prices, especially from buyers wary of greenwashing allegations
Who buys carbon credits?
The voluntary carbon market (VCM) is driven by corporate buyers using credits to offset emissions they cannot yet eliminate, as part of net zero or carbon neutral commitments. Major buyer categories include:
- Large corporates with public net zero targets (consumer brands, airlines, financial institutions)
- Smaller companies seeking carbon neutral certification for products or services
- Event organisers offsetting conference, festival or travel emissions
- Individuals offsetting personal or travel footprints
Credits typically reach buyers through brokers, specialist traders, or direct procurement from project developers. The largest registries - Verra and Gold Standard - publish public retirement records, so buyers can verify that the credits they purchased have been properly cancelled.