Permanence

What is a Carbon Credit Permanence?

Permanence refers to the longevity and durability of the emission reductions or removals achieved by a project. It assesses the risk that the sequestered carbon could be re-released into the atmosphere, thereby cancelling out the climate benefits.

Additionality, Permanence, and Leakage all need to be evaluated together in order to determine the quality of a carbon credit project.

Significance of Permanence

Permanence is critical in ensuring the long-term effectiveness of carbon credit projects. A project with poor permanence is considered to be of low integrity, as it cannot guarantee any long-term impact. For instance, if a reforestation project fails to look after its trees and they are later cut down or burnt, the sequestered carbon would be released back into the atmosphere. Therefore, permanence is essential in ensuring that the positive impacts of a carbon offset project are sustained over time.

Assessing Permanence in Projects

Projects are evaluated for risks such as natural disasters, policy changes, or economic shifts that could compromise the project's longevity.
The time period for which carbon is expected to be sequestered is considered. For example, forestry projects often have different risk profiles compared to technological carbon capture solutions, since Nature Based Solutions typically store carbon for much shorter periods than Technological Based Solutions.
Projects often include strategies to mitigate risks to permanence, such as insurance mechanisms, diversified project activities, or buffer pools of credits.

Permanence and Durability of Different Project Types:

High quality carbon storage methods such as mineralised CO2, CO2 in concrete, and ocean alkalinity have an expected storage time of over 100,000 years, presenting no practical risk of reversal.

Methods such as geological storage of liquid CO2, biomass burial, deep sea storage of CO2, and soil biochar have an expected storage time of over 1000 years, presenting a very low risk of reversal.

Forest carbon, coastal blue carbon, soil carbon, and untreated biomass in soil have an expected storage time exceeding 100 years, however these projects do present a risk of reversal due to the possibility of natural disasters.

Lastly, projects that involve things such as deferred forest harvesting have an expected storage time of about a year, offering temporary permanence since most or all of the CO2 will be released upon harvesting.

Permanence in different types of carbon removal and carbon avoidance projects

Challenges in Ensuring Permanence

The very long term storage solutions are subject to technological barriers that prevent the solutions from scaling to significant levels.
Natural disasters like wildfires, pests, or climate-induced changes pose significant risks to the permanence of nature-based projects.
Continuous monitoring is necessary to ensure that the projects remain effective over their intended lifespan, and this can be difficult with certain types of projects.