What Is Permanence in Carbon Credits?

Permanence refers to the durability of a carbon project's climate benefit, specifically the risk that stored or avoided carbon could be released back into the atmosphere. It is one of the ten Core Carbon Principles set by the ICVCM, and one of the most contested concepts in carbon credit integrity. The core tension: can carbon stored in trees for decades truly compensate for fossil CO₂ that persists in the atmosphere for centuries? For buyers and developers alike, understanding permanence is essential to evaluating credit quality and managing long-term risk.

Why Permanence Matters for Credit Integrity

Carbon credits represent a climate outcome: one metric ton of CO₂ equivalent reduced or removed. But that outcome is only as valuable as it is lasting. If a forestry project burns down or a land-use change reverses stored carbon, the credits issued against those reductions lose their environmental basis.

This is known as a reversal. Reversal risks vary widely by project type. Nature-based projects, such as REDD+ and afforestation/reforestation, face physical threats including wildfire, drought, pest outbreaks, and illegal logging. Engineered removal projects, like biochar or direct air capture with carbon storage (DACCS), store carbon in far more durable reservoirs, often for centuries or millennia, but come at higher cost per ton.

The practical benchmark used across most standards is 100 years. If a project can demonstrate that its carbon storage will persist for at least a century, with safeguards in place against reversal, it is generally considered to meet the permanence threshold.

How Registries Manage Reversal Risk

The primary mechanism for addressing non-permanence in the voluntary carbon market is the buffer pool. Registries require nature-based projects to set aside a percentage of issued credits into a pooled reserve. If a reversal event occurs, credits from the buffer are cancelled to compensate for the lost carbon.

Buffer pool designs differ across registries. Verra's VCS program uses a risk-adjusted approach, with project-level contributions starting at a minimum of 10%, determined by non-permanence risk assessments covering internal, external, and natural risk factors. Gold Standard applies a flat 20% contribution rate. ACR and CAR also maintain buffer pools with varying structures.

Despite their widespread use, buffer pools face growing scrutiny. The ICVCM's first Continuous Improvement Work Program on permanence, published in May 2025, recommended standardizing reversal definitions, stress-testing buffer reserves, and exploring novel compensation mechanisms such as permanence trusts.

The deeper debate goes beyond buffer mechanics. Some stakeholders argue that biological carbon storage, which is inherently reversible, should not be treated as equivalent to avoided fossil emissions, which are permanent by nature. The Article 6.4 Supervisory Body under the Paris Agreement rejected the "tonne-year" accounting approach on these grounds, reinforcing the view that temporary storage and permanent mitigation are fundamentally different climate outcomes. This distinction is increasingly shaping how buyers, rating agencies, and regulators evaluate credit quality.

The Permanence Spectrum: Nature-Based vs. Engineered

Not all carbon storage is equally durable. The market increasingly distinguishes between projects along a permanence spectrum.

At one end, forestry and soil carbon projects store carbon in biological reservoirs vulnerable to disturbance. These projects deliver critical co-benefits, including biodiversity protection and community livelihoods, but require ongoing monitoring and MRV to track reversal risk over decades.

At the other end, engineered removals like biochar (which locks carbon in stable soil amendments for hundreds of years) and geological storage (which sequesters CO₂ underground) offer far greater durability. Verra has proposed a long-term reversal monitoring system that could extend oversight of nature-based projects up to 100 years post-crediting, reflecting the need to close this durability gap.

For buyers, the distinction matters. Credits from projects with higher permanence risk are typically priced lower, while durable removal credits command significant premiums, often ranging from €50 to over €250 per ton for CCP-approved categories.

Key Takeaway

Permanence is the foundation of carbon credit value. Without confidence that stored carbon will remain out of the atmosphere, the environmental claim behind every credit weakens. As the ICVCM refines its permanence requirements and registries adopt stronger monitoring tools, buyers should prioritize credits with transparent reversal risk management and robust buffer or insurance mechanisms. Understanding where a project sits on the permanence spectrum is now a core part of carbon credit due diligence.