Most explanations of how biochar carbon credits work stop at the market: biomass is heated, an auditor checks the paperwork, a credit appears on a registry. That skips the part that decides whether the credit exists at all. A biochar credit is an accounting claim about a physical process, and almost every requirement in the crediting methodologies traces back to a specific decision inside the plant: what goes into the reactor, how hot it runs, what happens to the gas, and where the solid carbon ends up.
We build gasification and waste-to-energy systems and run the carbon credit side as a service, covering project certification, trading strategy and MRV. This is the chain as it looks from both ends.
What a Biochar Carbon Credit Actually Certifies
One credit represents one tonne of CO2 equivalent removed from the atmosphere and stored durably. The word removed is doing heavy lifting: this is not a tonne that was prevented from being emitted, it is a tonne that plants pulled out of the air and that a thermal process then locked into a solid instead of letting it decay back. If that distinction is new, carbon credits and carbon offsets are not the same instrument either.
The storage claim is long. The Puro Standard credits biochar at 200 years or more of storage with low reversal risk, which is why biochar sits in the durable carbon dioxide removal category rather than alongside forestry. The Integrity Council's framing is that decomposing plant matter is a carbon neutral cycle and biochar makes it carbon negative by interrupting it.
Step One: Pyrolysis Turns Loose Carbon Into Stable Carbon
What happens in the reactor
Biomass is heated in a sealed, oxygen starved chamber. Without oxygen it cannot burn, so instead of flames you get thermal decomposition. Between roughly 350 and 700 degrees Celsius the material breaks apart into three outputs: solid biochar, bio-oil, and syngas that can be burned to power the process itself. Our own five step process puts that syngas to work as dispatchable electricity and heat, with the biochar and the verified CO2 offsets coming off the same plant. The mechanics of that energy side are covered in our explainer on how waste-to-energy works.
Why H/Corg is the number that matters
Heat drives off the volatile fraction and rearranges what remains into stacked aromatic rings. Microbes that would happily eat fresh plant matter struggle with that structure, which is the entire basis of the permanence claim. The standard test for how far that conversion went is the ratio of hydrogen to organic carbon. Major standards certify at an H/Corg below 0.7, and below 0.4 is treated as highly stable. Lower means more condensed, more aromatic, harder to decompose.
That single lab number is not a quality badge. It feeds directly into the tonnage calculation, as the next section shows.
Gasification counts, torrefaction does not
A point that surprises many project developers: pyrolysis is not the only eligible route. Under Verra's VM0044, a range of thermochemical conversion processes qualify, including pyrolysis, gasification and biomass boilers, while torrefaction and hydrothermal carbonization are explicitly excluded. A gasification plant built primarily to make power and heat can therefore generate biochar credits from its char output, provided the rest of the requirements hold.
Step Two: Turning Tonnes of Biochar Into Tonnes of CO2
This is where most published explainers go quiet, and it is the part a developer needs.
Gross carbon stored. The tonnes of CO2e in the biochar are calculated from its organic carbon content, usually measured directly on a representative sample in a laboratory, with literature or IPCC default values used where lab access is limited. As a rough order of magnitude, one tonne of biochar corresponds to something like two to three tonnes of CO2, with the exact figure set by feedstock and pyrolysis conditions.
The permanence factor. Nobody credits the gross figure. The H/Corg ratio is converted into a persistence factor that models how much carbon is still there after a defined period. Verra derives the stable carbon content over a 100 year period from the 2019 Refinement to the IPCC Guidelines, with project specific factors from peer reviewed literature as an option. The European Biochar Certificate takes the most conservative widely used position, assuming 0.3 percent of the carbon is lost every year, which still leaves 74 percent stored after a century.
The deduction ledger. Everything the project itself emitted comes off: pre-treatment, conversion, auxiliary energy, processing and application, and transport where distances exceed the methodology threshold. Deducting process emissions and a permanence discount to arrive at net tCO2e is the core logic of the whole instrument.
A baseline of zero. Counterintuitively, protocols do not credit you for the emissions that would have happened if the residue had rotted or been burned. Baseline emissions are set to zero, a deliberately conservative convention that avoids counting the same carbon twice, once as avoided decay and once as stored solid.
The net result of those four moves is the number that becomes credits. It is always smaller than the carbon in the biochar, and a project that has not modelled the deductions before building has not modelled its revenue.
Step Three: The Chain From Feedstock to Issued Credit
The IETA business brief sets out the typical crediting sequence: eligible biomass is sourced and converted; the biochar is characterised for carbon content, stability, durability and contaminants; it is applied in an approved end use; net removals are quantified after lifecycle emissions and any buffers; monitoring and reporting run continuously; an independent third party verifies; credits are issued.
Two of those steps carry most of the practical burden.
Monitoring, reporting and verification. From first production you are logging feedstock origin, quantity and type, pyrolysis temperatures and residence times, yield and quality measurements, application records and process emissions. There is more on the audit machinery in our guide to how carbon credits are verified.
Additionality. VM0044 handles this with a standardised activity penetration test: the total waste biomass converted to biochar worldwide must remain at or below 5 percent of the total available. That is unusually mechanical compared with project by project additionality arguments, and it is one reason biochar documentation is comparatively tractable. Once credits are issued, selling biochar carbon credits is its own process.
Where the Plant Decides the Credit
High technology and low technology facilities
Methodologies do not treat all producers alike. VM0044 classifies a facility as high technology only if it recovers or combusts the greenhouse gases produced during pyrolysis, uses at least 70 percent of the heat energy produced, has pollution controls meeting local, national or international emission thresholds, and measures and reports production temperature. Miss any of the four and the facility is low technology, which restricts it to soil applications and forces more conservative carbon values.
Read that list again as an engineering specification rather than a compliance list. It describes an integrated plant that captures its own waste heat and cleans its own off gas, which is the same design a waste-to-energy project would build for economic reasons anyway. The hardware choices behind it, from batch kilns through to continuous units, are compared in our sister company's guide to biochar production equipment.
Feedstock: waste only, and what that includes
Eligible feedstock must be purely biogenic waste biomass that would otherwise have decayed or been combusted for non-energy purposes. Purpose grown biomass is not allowed, because using productive land to grow biochar feedstock competes with food security and risks land use change.
Sewage sludge sits inside the eligible list: biosolids are permitted, subject to heavy metal and contaminant thresholds appropriate to the intended end use. For a municipality with a sludge disposal obligation, that is the whole business case in one sentence. The contaminant profile is what decides whether the resulting char can go to soil or only into non-soil applications such as cement or asphalt, and only high technology facilities may use the non-soil route at all.
Pre-treatment is not a detail
Feedstock arrives wet, inconsistent and variable, and the reactor does not care about your intentions. We have argued publicly that thermal pre-treatment is non-negotiable in gasification and pyrolysis, for moisture reduction, energy density and feedstock homogenization. In credit terms, homogeneous feedstock produces consistent H/Corg results batch after batch, and consistency is what an auditor is actually testing. Erratic input shows up as erratic char quality, which shows up as conservative assumptions and lost tonnes.
What the Credits Are Worth and Who Buys Them
Biochar is not a fringe pathway. It was 89.4 percent of the 116,800 tonnes of durable CDR delivered in Q2 2025, and by Q1 2026 it accounted for 93 percent of a record 2.3 million tonnes contracted, with Microsoft signing 1.24 million tonnes with Exomad Green in Bolivia and Google committing 100,000 tonnes with Varaha in India. Prices in 2026 run from about 100 to 210 euro per tonne, with roughly 130 euro as the Nasdaq and Puro benchmark average and European projects at the top of the band. Our note on what biochar credits sell for per tonne goes into the drivers behind that spread.
Where Biochar Credits Can and Cannot Be Used
Biochar credits are voluntary market instruments. Issuing bodies include Puro.earth, Verra, Isometric, Climate Action Reserve and Carbon Standards International, and several methodologies have earned CORSIA eligibility or a CCP label from the Integrity Council.
Compliance market eligibility is another matter and remains limited. It is most advanced in Japan, where biochar is covered by J-Credit methodology AG-004 and those credits can be used within the GX-ETS subject to limits, while forthcoming carbon removal provisions under the EU or UK emissions trading systems are considered unlikely to include biochar. Any supplier implying that a biochar credit will discharge an EU ETS obligation is describing a market that does not exist yet. That is one of several reasons to look hard at whether biochar carbon credits are reliable before signing an offtake.
FAQ
How many carbon credits does one tonne of biochar generate?
In the region of two to three tonnes of CO2e before deductions, though the figure is set by feedstock and pyrolysis conditions and confirmed by laboratory measurement of organic carbon content, not assumed. Process emissions and the permanence factor are then subtracted, so the issued number is always lower than the gross carbon stored.
How long does biochar have to store carbon to qualify as durable removal?
Durable removal is generally defined at 100 years or more, and the Puro Standard credits biochar at 200 years or more with low reversal risk. Crediting does not treat storage as permanent: a persistence factor derived from the H/Corg ratio models the carbon still present at the end of the accounting period.
Can biochar made from sewage sludge earn carbon credits?
Yes. Biosolids are an eligible feedstock under VM0044, provided they meet the relevant heavy metal and contaminant thresholds for the intended end use. Those thresholds, rather than the crediting rules, usually decide whether the char goes into soil or into non-soil applications such as construction materials.
Who receives the credits, the biochar producer or the buyer of the biochar?
Credits are awarded to the project developer, which is most commonly the producer, since their process is what converts the carbon into a durable form. Ownership can be conveyed to another party, such as the end user, through a documented agreement.
Do biochar carbon credits count towards compliance obligations?
Mostly not. They are voluntary market instruments. The clearest compliance route today is Japan's J-Credit methodology AG-004, usable within the GX-ETS subject to limits, and inclusion in forthcoming EU or UK ETS removal provisions is regarded as unlikely.
What makes one biochar credit better than another?
Three pillars: sustainably sourced or genuinely waste feedstock, transparent MRV covering feedstock through to final application, and evidenced permanence. Weak lifecycle assessment, unmonitored end use and leakage are the recurring failure modes, which is why buyers ask for feedstock origin, a full LCA and expected permanence before purchase.