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Permanence in carbon offsetting, explained
Permanence in carbon offsetting, explained
Permanence is a key marker of quality in carbon offsetting projects. What does permanence mean? And why is it so important? Let’s find out.October 3, 2022
Illustration depicting permanence in carbon offsetting (illustrative purposes only)

If you’re exploring the world of carbon markets you’re bound to have come across the term ‘permanence’.

It’s an important concept to understand, because permanence is one of the key differences between high and low-quality offset projects (alongside additionality, single-counting, accuracy of estimations, and co-benefits).

So what does permanence actually mean in terms of carbon offsets? And how can you identify it when evaluating projects? 

That’s exactly what we’ll explore in this article, covering:

  • A definition of permanence
  • How permanence is determined and accounted for projects
  • Is it ever ok to buy carbon credits in a non-permanent offset project?

Understanding the basics: defining permanence

First, let’s start with a simple definition:

Permanence refers to how durable the carbon benefit from an offset project is, taking into account the risk of reversal. 

Permanence is typically used as a measure of quality in carbon offsetting projects which involve storage – because in projects with no storage (i.e. emissions reductions projects like renewable energy and methane reduction in the dairy industry) the risk that the carbon benefit will be reversed is much reduced. 

Permanence is how durable the carbon benefit from an offset project is. This takes into account the risk of that benefit being reversed earlier than expected, for instance if a wildfire kills trees in a reforestation project before the end of the project's lifetime.

Some of these projects provide a ‘permanent’ storage for carbon – typically storage is seen as permanent if the carbon will be stored for at least 100 years. Other types of projects provide storage which is only temporary, meaning that the CO2 will be re-released into the atmosphere at a later date. 

Given that carbon emissions stay in the atmosphere for 300 to 1000 years once emitted, it isn’t enough to compensate for emissions through offsets where CO2 is only stored for the short term. This is only delaying the inevitable planetary harm of the emissions – which is why permanence is such an important concept in offsetting, and why it needs to be accounted for by carbon offset projects. 

Diving deeper: how permanence is determined and accounted for

In general terms, carbon credits are issued based on the environmental value they provide. 

With projects that do provide permanent storage, this is fairly straightforward – carbon credits are issued based on how many tonnes of CO2e the project will avoid or remove, with 1 carbon credit equivalent to 1 tonne of carbon emissions which has either been prevented from happening (emissions reduction projects) or removed from the atmosphere (carbon removal projects).

This applies to:

  • Carbon removal projects with long-lived storage – biochar, enhanced weathering, Direct Air Capture, seaweed farming, bio-oil sequestration. These projects provide permanent stores for carbon, and so when evaluating offset projects you can be sure of a high level of permanence. For instance, in biochar projects carbon is converted into a solid form, which can then be used for soil fertiliser. 
  • Emissions reduction projects with long-lived storage – carbon capture and storage e.g. on fossil fuel plants or industrial facilities. Again, these projects provide permanent storage for CO2, typically pumped deep underground. 

But, some projects provide only short-lived storage, and in these cases there is a high risk of reversal happening – and this is where permanence needs to be taken into account when issuing carbon credits:

  • Carbon removal projects with short-lived storage – reforestation, afforestation, improved forest management, soil carbon enhancement, ecosystem restoration e.g. restoring wetlands.
  • Emissions reduction projects with short-lived storage – projects which avoid damage to ecosystems e.g. forest conservation.

These are natural solutions where carbon is stored in the land’s natural sinks (like forests). The storage is short-term because the carbon will eventually be returned to the atmosphere. 

Ideally, this occurs at the end of the natural cycle. For example, when a tree dies it will return some of the CO2 it had absorbed to the atmosphere as part of the natural carbon cycle (a common myth is that all of the CO2 absorbed by the tree is released – actually much of it is absorbed by and stored in soil). 

But, these projects with short-lived storage also carry risks that CO2 may be released earlier than nature intended. With forestry projects, for instance, tree disease or wildfires could arise, a change in the land-use could lead to the trees being cut down, or a change in the land-owner could mean the forest is badly managed and trees do not survive to their expected age. 

These risks make it difficult to predict exactly how long the carbon will be stored for, and so these kinds of projects cannot be said to be permanent – making them less high-impact than those projects which do provide permanent storage.

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So, is it ever ok to buy carbon credits in a non-permanent project?

Permanent projects are generally seen as the highest impact form of carbon offsets – removing CO2 from the atmosphere and permanently storing it, so that it can never contribute to climate change.

But, that doesn’t mean that it’s never ok to buy carbon credits in a non-permanent project. To safely buy carbon credits from non-permanent carbon offset projects:

  • Always support high-quality projects. High-quality projects take permanence into account when planning the project and how it will be managed, putting systems in place which reduce the risk of carbon benefits being reversed early.
  • Opt for a portfolio approach. Making a portfolio of different carbon offset projects that you buy carbon credits from means you can balance out cost and the immediacy of impact – non-permanent projects are (currently) cheaper and are typically already in operation, meaning the carbon benefit is instant, so including them in a portfolio does make sense.

A little more detail on both of these ...

Always support high-quality projects that take permanence into account

The big issue is when projects are non-permanent, and when they don’t make any effort to ensure that the project brings as permanent and durable carbon benefit as possible – this is a sure-fire indicator of low-quality.

In high-quality projects the impermanence will have been taken into account when issuing carbon credits and systems will be in place to reduce the risk of reversal.

The Gold Standard (a renowned carbon offset certification organisation), for instance, accounts for impermanence in land-based projects by asking the project developer to place 20% of the carbon credits issued to them into a ‘compliance buffer’ which is centrally held by the Gold Standard – the ‘Gold Standard Buffer’.

This acts as an insurance policy to account for any loss of carbon storage e.g. if a forest fire occurs in a forestry project. The Gold Standard also requires regular monitoring and reporting on projects to ensure that performance is as expected, and projects which underperform go through a compliance process to get them back on track – providing assurance to carbon buyers that the project will provide the expected carbon benefits.

Plus, project developers can actively reduce the risks of impermanence in the process of developing and managing the project. Keeping with the example of a carbon forestry project, this would include:

  • Careful management of young saplings to protect them from disease, animal damage, wildfires etc and to ensure they can access the water, nutrients, sunlight etc needed to thrive – it’s crucial that the trees that are planted reach maturity.
  • Robust and regular monitoring of the project area to improve forest management and reduce the risk of natural disasters wiping out the forest.
  • Working with the landowner to minimise the possibility that the land the trees are planted on could change ownership or land use in the years and decades to come, to avoid the trees being cut down or damaged once mature.

A great example of this is the Ackron Mixed forest – learn more about how the project is managed and monitored in our deep dive on afforestation as a carbon offset project type.

The planned duration of a project is also an important component: often known as the project lifetime.

For instance, if a project developer has planned a 10 year carbon forestry project we can be confident that the forest will be there for 10 years because the developer has a responsibility to ensure that’s the case, but we have no clue if the forest will still exist once that 10 years is up (at Lune, we’d therefore calculate this as a permanence of 10 years, because we can’t predict what happens after that point). But, if a project has a 50 year or 100 year lifetime, then we can be much more confident of the permanence of the carbon removal.

So, when you’re evaluating carbon offset projects based on permanence, you should be looking for:

  • Evidence of long-lived (permanent) carbon storage, or…
  • Evidence of impermanence being taken into account and mitigated – a high-quality project should be open and transparent about this, and make reference to the organisation which has certified them, and…
  • The lifetime of the project – the longer the commitment of the developer, the better.
Opt for a portfolio approach to balance cost and impact

Carbon credits in permanent carbon removal projects are also currently significantly more expensive than non-permanent ones.

That’s because permanent carbon removal relies on new technologies and methodologies (Direct Air Capture, biochar, seaweed farming etc) which are still being researched, developed, and scaled up. They have huge potential as ways to remove and store large amounts of carbon in the future – but they require large amounts of investment to get there.

In contrast, non-permanent projects such as forestry projects don’t require the same level of technology, and so carbon credits in these projects are currently much more affordable. Plus, these projects are well-established and relatively easy to set up, so they provide carbon benefits right now.

Whilst we’d recommend that businesses do support those early-stage, permanent carbon removal projects with a high potential impact where possible, we also know that cost is inevitably a factor in business offsetting. Plus, funding projects which can immediately remove CO2 from the atmosphere has immediate positive impacts and ‘buys’ time to develop those high-potential permanent removal technologies. 

That’s why we often recommend that businesses take a portfolio approach – building a portfolio of different project types across emissions reduction and carbon removal, short and long-lived storage. This balances out having immediate impact now with funding future high-impact removals, as well as balancing out overall cost. 

The Oxford Principles for Offsetting offer a framework for this kind of portfolio approach to offsetting – how to build a high impact portfolio, as well as how to adapt that portfolio over time to maintain impact and support the development of the carbon market. As an example, here's what global design company IDEO's carbon offsetting portfolio with Lune currently looks like, aligned with the Oxford Offsetting Principles:


Our advice on evaluating carbon offset projects

Choosing the right projects to support is crucial to any carbon offsetting activity, and as you can see from this explainer on permanence, that isn’t a simple process.

If projects aren’t high-quality they may not actually be making any real difference (even doing more harm than good in some cases) – and, for businesses, that leaves us open to allegations of greenwashing. 

One of the key benefits of working with a sustainability partner you trust is that the stress of evaluating projects for quality is taken away from you.

For instance, at Lune we have an established methodology for evaluating project quality, and our library of hand-picked carbon offset projects contains only the projects we’ve identified as being the highest quality. Plus, we also enable businesses to easily create a portfolio based on the Oxford Offsetting Principles, so purchases are aligned with expert research too. 


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