Not all stored carbon stays stored. Biochar permanence — carbon held in soil for 100 years and beyond — is what separates a durable carbon removal from a credit that can quietly come undone, and it changes what the project has to prove.
Every carbon credit is a claim about the future as much as about the past. It says a tonne of CO₂e was removed or avoided, and that it will stay that way. Biochar permanence is the reason the second half of that claim is unusually easy to defend: pyrolysis converts biomass into a stable form of carbon that remains in soil for centuries, and no decision taken in the following season reverses the chemistry.
That single property reorganises everything downstream — what the credit is worth defending, what a buyer is actually purchasing, and where the measurement effort has to go.
What biochar permanence actually means
Left alone, crop residue and other biomass return their carbon to the atmosphere within a season or two as they decompose or are burned. Pyrolysis interrupts that. What comes out is a stable carbon structure that stays locked in soil for 100 years and beyond, while also enriching soil fertility, helping retain moisture and reducing greenhouse gas emissions from agriculture.
The yield is what makes it material at project scale: roughly 2.5–3 tonnes of CO₂e per tonne of biochar produced. Permanence and yield are separate numbers doing separate jobs. Yield sets how many credits a batch can generate. Permanence sets how long the claim behind them holds — and, in practice, how much scrutiny it can withstand.
Durability is not a promise to maintain something for a century. It is a property of the material, fixed the moment the batch cools.
Storage that can reverse, and storage that cannot
Set biochar beside the other pathways in a nature-based portfolio and the difference is structural rather than a matter of degree.
- Agroforestry sequesters 5–15 t CO₂e per hectare per year into living biomass. Real carbon, and measurable tree by tree — but it is standing in wood, and it stays sequestered only while the trees stand.
- Mangrove blue carbon is denser still, 3–5× a typical forest, with soil carbon stable for 1,000 years and more. That soil store is exceptionally durable, but it depends on the coastline staying intact and unconverted.
- Rice methane pathways — AWD and DSR — are avoidance rather than removal. AWD can cut greenhouse gas emissions by up to 50%, and the Gold Standard DREAM methodology quantifies up to 48% methane avoided per season. The benefit is genuine, and it is renewed each season, because the practice has to be repeated each season to earn it again.
Biochar sits at a different point on that spectrum. Once a batch has been produced and applied, the following year’s cropping decisions, land tenure and weather add nothing to the carbon already fixed in it and take nothing away. That is what durable carbon removal buys: a claim that does not need the field to behave for a century.
Why durable carbon removal is bought differently
Biochar is a removal rather than an avoidance, a distinction covered in what a biochar dMRV system must capture. Permanence is the second axis, and it is the one a buyer tends to ask about immediately after the first.
The reason is arithmetic on the buyer’s own side. An emission released today sits in the atmosphere on a timescale of centuries. Offsetting it with storage that lasts a few seasons does not close the account, it defers it, and the liability returns when the storage does. Storage measured in centuries matches the timescale of the emission it is set against, which is why durability, and not only volume, belongs in the purchase decision.
For a project developer that cuts both ways. A durable removal is the stronger asset, and it is held to the stronger standard of proof, because there is no annual re-measurement cycle in which an over-claim would surface and correct itself.
Permanence is settled in the kiln, not in the paperwork
Nothing recorded after the fact makes a batch more permanent. Durability is fixed by the material and the conditions it was produced under, which leaves the MRV system one job: to establish credibly that a specific quantity was made, and applied.
That is where durable removals are actually lost. Not to reversal, but to records that cannot carry the claim. A batch with no logged feedstock cannot be tied to its yield. An output with no application record cannot be shown to have been stored rather than sold on. The carbon is in the ground either way; the credit is not.
What has to last as long as the carbon does
A hundred-year claim is audited years after the batch is cold, often by people who were not there and cannot re-run the production. The evidence has to outlive the phone it was captured on, the staff member who captured it, and the season it belonged to.
- Captured at the event, not afterwards — feedstock and production parameters logged as the batch runs, rather than reconstructed from memory later.
- Location-stamped — GPS attached automatically, so every record carries traceability a verifier can check independently.
- Offline by default — production happens where the biomass is, which is rarely where the connectivity is. Records are written on the device and sync when there is a signal.
- Held securely for the long term — backed up in cloud storage under our ISO/IEC 27001:2022 certified information security management system, because a durable claim needs durable custody of its evidence.
- Visible while the project runs — reporting and trend dashboards, so gaps surface during production rather than at verification, when they can no longer be filled.
Questions worth settling before you claim durability
Four decisions determine whether a permanence claim survives contact with a verifier, and all four are cheaper to make before the first batch than after the hundredth:
What is credited, and over what horizon
The methodology sets the storage horizon the credit is issued against. Establish it first, because it determines which evidence is worth collecting at all.
How output quantity is established
The sequestration estimate is calculated from biochar out. Who weighs it, and how, is the foundation under every tonne claimed.
Where the biochar went
Application location, captured at the point of spreading. Storage with no recorded destination is an assertion rather than a record.
Who can produce the record in year five
Custody, backup and access. A durable removal that cannot be evidenced later is indistinguishable from one that never happened.
Answer those four and biochar permanence stops being a line in a pitch deck and becomes what it ought to be: the most defensible part of the project.
Related reading
The Biochar dMRV app page covers the platform and the field capture in detail, and DMRV methods sets biochar alongside the other pathways we measure.
- Biochar carbon credits: what a dMRV system must capture
- Mangrove blue carbon credits: the densest carbon on the coast
- Agroforestry carbon credits: what farmers earn, and how it is verified
- Why agricultural carbon data fails audit
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