An avoidance credit represents emissions that were prevented from happening, so the carbon never entered the atmosphere. A removal credit represents carbon that was taken out of the atmosphere and stored. Avoidance depends on proving what would have happened otherwise, which is why it attracts far more scrutiny and lower prices.
Two different claims wearing the same label
A carbon credit nominally represents one tonne of carbon dioxide equivalent. That single unit hides two claims that are not equivalent at all.
Avoidance. A tonne that was going to be emitted, and was not. A forest that was going to be cleared and was protected instead. A coal plant that was going to be built, and a solar plant built in its place. The atmosphere never receives the carbon.
Removal. A tonne that is already in the atmosphere, taken out and stored. A tree growing and holding carbon in wood. Biochar buried in soil. Carbon captured directly from air and injected underground.
Both are useful. Only one of them can be verified by looking at what is physically there.
The counterfactual problem
This is the heart of it, and it is not a technicality.
To value an avoidance credit you must know what would have happened without the project. That is unobservable by definition. The forest was not cleared, so there is no way to confirm it would have been. The claim rests on a modelled baseline, and the party constructing that baseline is usually the party who benefits from it being generous.
The predictable result has followed. Investigations of forest protection credits have repeatedly found that projects claimed to be preventing deforestation that was not actually going to occur, or was going to occur at a far lower rate. The credits were real certificates representing very little.
A removal credit does not have this problem in the same form. You can measure the carbon that is present. You can weigh biochar. You can measure a tree. The question shifts from “what would have happened” to “how much is there and how long will it stay”, and both of those are measurable rather than hypothetical.
This is why removal credits command higher prices. It is not fashion. It is that one claim can be checked against physical reality and the other cannot.
The second axis: durability
Removal is not one category. Within it, the question that determines price is how long the carbon stays stored.
A growing forest genuinely removes carbon. It also holds that carbon only while it stands. Fire, felling, disease and drought all release it again, and a twenty year commitment is short against a molecule that will otherwise remain in the atmosphere for centuries. This is the permanence problem, and it is why forestry removal, though real, sits below durable removal in price.
Biochar sits at the other end. Pyrolysis rearranges plant carbon into structures that soil organisms find very difficult to break down, so once it is in the ground there is no straightforward path back to the atmosphere. Geological storage is similar in principle: carbon placed somewhere it cannot easily return from.
So the hierarchy that has emerged in serious buying is roughly this. Avoidance sits at the bottom, discounted for the counterfactual problem. Forestry removal sits above it, real but reversible. Durable removal sits at the top, because it is both measurable and difficult to undo.
Why this decided our own design
We restore land, which produces forestry removal, and forestry removal carries the permanence discount described above. Rather than argue with that discount, we treat it as information.
Residue from the restoration is pyrolysed into biochar. That converts a portion of the same biological carbon into a durable form, and it does so with material that would otherwise decompose within a few years and return its carbon anyway. The forest is still there and still removing. The char is the part of the output that survives the durability question.
It also solves a practical problem. Biomass on remote or arid land is often uneconomic to transport to a buyer, and pyrolysis converts a haulage problem into a storable product while returning a soil amendment to exactly the ground that needed it.
What to ask before buying any credit
Four questions, in this order. They separate credits worth buying from certificates worth nothing.
Is this avoidance or removal. If avoidance, who constructed the baseline and what evidence supports the counterfactual. Treat a generous baseline as the default assumption until shown otherwise.
If removal, how durable. Ask for the expected storage duration and what physically could reverse it. A project that cannot answer this has not thought about it.
How was it measured. Not modelled, measured. Ask for the sampling method, the sample size and the uncertainty. A figure quoted without a method behind it carries no information, however precise it looks.
Who verified it, and are they independent of the seller. Self reported measurement is data. It is not verification, and any seller who blurs the two is telling you something about the rest of their claims.
Those are the same questions we expect to be asked about our own output, which is why our measurement method is published before the numbers are.
Related questions
- Why are avoidance credits criticised more than removal credits?
- Because an avoidance credit is a claim about something that did not happen. Establishing its value requires proving what would have occurred in the absence of the project, which cannot be observed and has to be modelled. Where that modelled baseline is generous, the credit represents less benefit than it claims, and this has been found repeatedly in forest protection projects.
- What does permanence mean in carbon credits?
- Permanence is how long the carbon stays out of the atmosphere. A forest holds carbon only while it stands, so fire, felling or drought can reverse the removal, which makes it impermanent. Carbon stored in a chemically stable form such as biochar, or injected into geological storage, is far more resistant to reversal and is described as durable.
- Are avoidance credits worthless?
- No. Preventing an emission is genuinely valuable, and some avoidance projects are well constructed and honestly baselined. The problem is that the quality of an avoidance credit cannot be verified by inspecting the credit itself, and buyers who have been embarrassed by low quality credits have responded by discounting the whole category.