Every project type has trade-offs. Avoidance credits are cheap but carry no stored carbon; nature-based removals store carbon but can be reversed; engineered removals last for centuries or longer but cost many times more. A portfolio approach buys across these types on purpose, so no single weakness dominates. This page explains why buyers blend credits, how guidance says the mix should change and how to build one. It is part of our guide to carbon credit project types.
Why blend credit types?
Three reasons come up again and again.
- Cost. In 2024, reduction credits averaged $4.05 per tonne and removal credits $19.50, a premium Ecosystem Marketplace put at 381%Source 2. Buying only durable removals is expensive for most budgets.
- Risk. Different types fail in different ways: over-crediting, reversal by fire or clearance, or slow measurement. Spreading purchases limits the damage if one project disappoints.
- Supply. The Oxford Offsetting Principles say supply of all types of high-quality carbon removal is still very limitedSource 1, and recommend supporting a diverse portfolio of removal and storage technologies to avoid over-reliance on any one approachSource 1.
Matched shop
Buy portfolio credits
- Registry serial numbers
- Retirement certificate
- Project documentation
How the mix should change over time
The Oxford Principles set out how a net zero aligned mix should move. They group projects into five kinds, from avoided emissions without storage, such as renewable energy and efficiency, through avoided ecosystem loss, to carbon removal into the biosphere and, with the lowest risk of reversal, into the geosphereSource 1.
- Today: mostly reductions, some removals. Emission reduction projects have an important role over at least the next decadeSource 1.
- Shift toward removals. Buyers using credits toward net zero should increase the share from carbon removal, aiming for 100% removals by the global net zero date, 2050 at the latestSource 1.
- Shift toward durable storage. Within removals, move toward storage with a low risk of reversal, such as geological storage or mineralised carbon, which can last centuries to millenniaSource 1.
Most buyers are a long way from that. Citing Berkeley Carbon Trading Project data to December 2023, the Oxford Principles report that 82.9% of credits retired across the four major registries came from emission reduction or avoidance projects, 13.8% were mixed reduction and removal credits, and only 3.3% were pure removalsSource 1.
The Oxford Principles add that an immediate shift to a 100% carbon removal portfolio may not be necessary or currently feasible for some, because removal projects need time to scaleSource 1.
Removals matter beyond offsetting too. The IPCC describes three complementary roles for carbon dioxide removal: lowering net emissions in the near term, counterbalancing hard-to-abate residual emissions to reach net zero, and achieving net negative emissions in the long termSource 6.
Building blocks of a portfolio
Scrolls sideways to show every column.
| Type | Kind | Average price 2024 (USD/t) | Typical role |
|---|---|---|---|
| Renewable energy | Avoidance | 2.67 | Low-cost contribution; additionality questions |
| REDD+ forest protection | Avoidance | 6.03 | Protects existing carbon stocks |
| Household devices incl. cookstoves | Avoidance | 7.30 | Health and livelihood co-benefits |
| Reforestation (ARR) | Removal | 20.44 | Nature-based removal; reversal risk |
| Biochar | Removal | Over 160 | Durable removal, small supply |
As of Oct 2026
Prices are Ecosystem Marketplace’s 2024 averages from reported dealsSource 2. Each type has its own page: renewable energy, forest protection (REDD+), clean cookstoves, reforestation and biochar. For storage that lasts longest, see direct air capture and enhanced weathering.
Quality first, then the mix
A portfolio of weak credits is still weak. Screen every component before thinking about proportions.
- Use a common quality bar. The ICVCM’s Core Carbon Principles set a threshold covering areas such as additionality, permanence and robust quantificationSource 5.
- Beware the price trap. The Oxford Principles describe a perverse price incentive to support weaker and cheaper projects, and too many projects with a high risk of reversal, short-lived storage and low integritySource 1.
- Check co-benefits and harms. The IPCC finds that the impacts of carbon removal on ecosystems and people vary widely by method, site and scaleSource 6.
Our guide to how to verify carbon credits covers the checks for each credit.
How companies use portfolios
For companies, the mix links to the claims they want to make.
- Credits are not reductions. The SBTi says credits must be reported separately from a company’s emissions inventory and do not count as reductions towards its targetsSource 3. VCMI says credits must be used in addition to, and not to delay or displace, deep cutsSource 4.
- Residual emissions need removals. Under the SBTi standard, emissions left at net zero must be neutralised by removing carbon from the atmosphere and storing it permanentlySource 3.
- Wider action can use any type. Beyond value chain mitigation, action outside a company’s value chain, can include avoiding, reducing or removing emissionsSource 3.
The Oxford Principles also suggest long-term purchase agreements, similar to power purchase agreements, to give removal developers the certainty they need to raise capitalSource 1.
A mix of credits is not a neutrality claim
Blending credits funds climate action elsewhere; your own emissions stay the same. Describe the tonnes and project types you funded, with links to their retirement records, rather than claiming your footprint is cancelled. See reduce vs offset for why cutting comes first.
A simple way to start
- Cut first and estimate what is left; the credits-needed calculator helps.
- Set a removal share you can afford now, and a plan to raise it each year.
- Choose two or three types that fail in different ways, each meeting your quality bar.
- Retire in your name and keep the records.