The Complete Guide to Carbon Credit Buffer Pools

If you've been involved with the voluntary carbon market for any length of time, you've probably heard the term "carbon credit buffer pool". But what does it actually mean?

In this article, we explain what a carbon credit buffer is, how these market mechanisms protect buyers, and why they're so important to the future of the carbon credits industry.

O que é um buffer de crédito de carbono?

The buffer pool acts as a safety net to ensure the integrity of previously issued credits.

Think of the buffer pool as an insurance policy that makes sure each carbon credit will deliver 1 ton of CO2 emissions removals or avoidance, even if some carbon stocks are unexpectedly lost.

In practice, this "buffer insurance" ensures project developers can't sell a carbon credit for every single unit of CO2 emissions that are removed or avoided. The total number of credits the project is permitted to sell is equal to the net emissions reductions or removals minus the buffer contribution and any other deductions. A portion of carbon credits generated by nature-based carbon credit projects is set aside and placed in a “buffer pool” or “buffer reserve” instead of being sold. Buffer credits can be canceled from the pool if a “reversal” takes place, with the aim to ensure the integrity of previously issued credits.

A reversal refers to the release of carbon emissions that were previously removed or avoided by the carbon project to the extent that the integrity of previously issued credits is called into question.

Reversals can be driven by both human and natural causes including logging, forest fires, and droughts. Buffer pools are typically only used for nature-based carbon credit projects, which have a more material risk of reversal than technology-based solutions.

The Wilder Carbon Buffer is a good example of a carbon credit buffer. This buffer insurance policy was created in 2024 and acts as a risk mitigation mechanism for the voluntary carbon market (VCM).

Como funciona o buffer?

The 4 biggest registries, Verra, Gold Standard, ACR and CAR all use buffer pools. However, their design and implementation varies slightly between registries and nature-based carbon credit project types.

Como os pools de buffer são estruturados?

‍Obuffer pool é gerenciado pelo registro e pode conter créditos de buffer de todos os projetos dentro do programa de registro em um único pool combinado, geralmente dividido por tipo de projeto, ou pode ser vinculado individualmente a projetos específicos. 

‍What happens if carbon stock is lost?

Nem todas as perdas de estoque de carbono em uma área de projeto resultarão no cancelamento de créditos do buffer pool. Os créditos não serão cancelados do buffer pool se, em uma base líquida, o projeto tiver evitado ou removido emissões durante um período de crédito.

Se não houver uma perda líquida de estoque de carbono na próxima verificação e o projeto tiver proporcionado mais reduções ou remoções de emissões do que a perda, os pools de buffer não serão usados.

Se houver uma perda líquida de estoque de carbono na próxima verificação, os créditos poderão ser cancelados do buffer pool. Entretanto, dependendo do registro, algumas ações alternativas podem ser tomadas, incluindo

• As vendas futuras de créditos podem ser reduzidas de forma correspondente
• Os créditos não vendidos podem ser cancelados
• Um número equivalente de créditos de carbono pode ser comprado dentro do mesmo registro, mas pode ser de um tipo de projeto diferente

If the loss of credits is extreme, and exceeds the project's individual contributions to the buffer pool or the project is terminated, the liability of the project varies. 

• Some registries, like ACR, require the project to either procure credits from another project or cancel credits from the buffer pool, equal to the total number of credits ever issued by the project. 
• O Verra, por outro lado, exige que os créditos sejam cancelados somente do buffer pool. Em um caso extremo, quando um projeto é encerrado antecipadamente ou não apresenta um relatório de verificação por 15 anos, o número total de créditos já vendidos pelo projeto será cancelado do buffer pool.

‍What happens if a project consistently performs well or reduces its non-permanence risk score?

‍If a project registered in Verra's VCS program performs well, a small portion of the project's buffer credits can be returned to the project. 

Up to 15% of the project's buffer pool credits can be released if the project performs well over a 5 year monitoring period by either decreasing its risk score or not drawing from the buffer. This can only occur at least 5 years after the credits were verified. 

Supondo que um projeto tenha contribuído com 10% dos créditos para o buffer pool, uma liberação de 15% equivaleria a apenas 1,5% das reduções de emissões verificadas. Como essa parcela é muito pequena, o projeto pode priorizar a implementação de atividades que reduzam o risco de reversão das reduções de emissões em vez de recuperar um número tão pequeno de créditos de buffer.

How are buffer pool contributions determined?

Contributions to the pool are either a standard flat rate that may be subject to change (i.e. 20% for Gold Standard) or determined on a risk-adjusted basis by project with minimum thresholds set by registries (i.e. Verra >10%). Buffer pool contributions are either made directly from the project's issuance or, in the case of ACR and Gold Standard, the project proponent can input credits from another project.

Where contributions are determined on a risk-adjusted basis, the contribution required for a specific project is based on the results of non-permanence risk assessments, carried out during each monitoring period. In the case of some registries, like Verra, a project's contribution to the buffer pool per issuance can go up or down over time depending on specific project level risks during each monitoring period and after a project has been required to cancel credits from the buffer pool.

Verra's non-permanence assessments reflect the risks to carbon stocks stemming from:

1. Fatores de risco internos, incluindo: atividades de gerenciamento do projeto, viabilidade financeira, custo de oportunidade de não manter os estoques de carbono armazenados, tempo restante do projeto
2. Fatores de risco externos, incluindo: posse da terra e direitos de propriedade, consentimento prévio informado, governança regional
3. Fatores naturais externos, incluindo: incêndios, pragas e doenças, condições climáticas extremas

Quando as contribuições ao buffer pool estão vinculadas a avaliações de risco de não permanência específicas do projeto, os projetos são incentivados a limitar suas contribuições e o uso do buffer pool para maximizar o número de créditos que podem vender e, portanto, a receita.

Tomando como exemplo o caso acima, em que um projeto teve de cancelar créditos do buffer pool devido a incêndios na área do projeto. Nesses casos, a parcela futura de créditos com que um projeto contribui para um buffer pool pode variar de acordo com o nível de ação adotado.

Nenhuma ou pouca ação adicional é tomada para mitigar o risco de futuros incêndios florestais:

• The risk to the project's carbon stock may be raised during the next monitoring period
• O projeto pode precisar enviar uma parcela maior de créditos para o buffer pool no futuro, reduzindo assim o número de créditos que um projeto pode vender

São tomadas medidas significativas para mitigar o risco de incêndios florestais a um custo para o projeto (por exemplo, adição de torres de monitoramento para que os guardas florestais detectem incêndios):

• The risk to the project's carbon stock may be held constant or even be reduced if additional response measures counteract the previously increased risk
• A parcela de créditos contribuída para o buffer pool pode ser mantida estável ou diminuir

Os pools de buffer são suficientemente robustos?

The size of the buffer pools relative to the number of credits issued varies by registry. In 2025, Verra's VCS currently has almost 77 million credits available in the buffer, less than 6% of the 1.3+ billion credits issued. There have not been many instances where the buffer pool has been drawn on.

Embora os pools de buffer tenham o objetivo de garantir a integridade de todos os créditos emitidos anteriormente, há algumas preocupações quanto à sua capacidade de fazer isso.

1. O tamanho do buffer pool em relação ao número de créditos de carbono pode não ser suficiente para proteger contra perdas catastróficas. 

• Analysis by Carbon Plan, investigated the impact of the 2020 Lionshead Fire in Oregon and estimated that the impact on a single project could erode between 4-11% of the total buffer pool of California's carbon market. Although risks are diversified between projects, a few catastrophic events could compound this impact and severely erode the buffer pool.

2. Para projetos VCS REDD+, as perdas só serão contabilizadas adequadamente se a linha de base não for inflada.

• REDD+ projects will only draw on the buffer pool if there is a net loss that exceeds the emissions in the baseline (business as usual) scenario. If the baseline is inflated, a very significant loss could occur and not be appropriately accounted for, thereby undermining the quality of previously issued credits. However, this is somewhat mitigated as inflated baselines result in inflated contributions to the buffer pool.

3. In some registries, credits can be purchased from other projects and project types that may not be of equivalent quality, instead of being removed from the buffer pool. 

• The quality of carbon credits is not uniform across the market. In the past, we reported that 25% of the REDD+ projects we have rated fall into our lowest rating category, Tier 3, indicating they have a very low likelihood of avoiding 1 ton of CO2 per carbon credit.
• Projects are incentivized to purchase the lowest cost credits, which may be of lower quality. In the case of Gold Standard, this can include credits from Clean Development Mechanism (CDM) projects, which aren't required to contribute to a buffer pool. 

O que está sendo feito para melhorar a robustez dos pools de buffer?

As with many elements of the VCM, increased scrutiny is being placed on the design and operation of buffer pools. In turn, registries and market bodies, like VERRA and CARB, are taking steps to update buffer pool requirements and non-permanence risk modelling to reflect the latest scientific thinking. 

Isso, combinado com os avanços na tecnologia de MRV, melhorias mais amplas nas metodologias de certificação e desenvolvimento de produtos de seguro para créditos de carbono, deve aumentar a robustez dos créditos de carbono e dos pools de buffer no futuro.

A importância das avaliações de risco de permanência

Climate change mitigation is essential. Because of this, the level of scrutiny directed toward the quality of carbon credits used by corporations is increasing.

Given potential limitations to the robustness of buffer pools under evolving climate risks, some buyers require an additional understanding of the risks facing credits they've invested in.

This is why Sylvera provides an independent reversal risk assessment via our permanence score and monitors project performance closely over time. Our permanence score assesses the likelihood and severity of natural risks that could impact the project, including fire, drought, pest, storm and flood risk, using in-house climate modeling. Risks stemming from human activities such as project structure, community engagement, and regional political and socioeconomic risks, are also assessed. This provides additional context to buyers looking to purchase high-quality carbon credits.

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