What does a lab check in a biochar sample for carbon credits?
Under Verra VM0044 v1.2 the lab gives you the two numbers that decide credits: organic carbon content on a dry weight basis, and the H:Corg ratio. Biochar for soil must also pass IBI, EBC or national contaminant limits. Only a lab accredited or approved by a national agency counts.
The tests and how often
- Organic carbon content: by IBI Biochar Testing Guidelines or EBC production guidelines, at least once a year and again after any material change in feedstock or production settings.
- H:Corg: every batch, for biochar going to soil.
- Moisture: checked for every batch, so biochar mass can be stated on a dry weight basis.
- Contaminants: heavy metals and organic contaminants against IBI, EBC or national limits, for soil use. If mineral additives such as lime or ash exceed 10% of the mass, lab tests must show the final product still meets those limits.
When you cannot test to standard
A low technology kiln that cannot sample organic carbon to the required standard uses the methodology's conservative defaults instead, for example 0.77 for wood and 0.74 for nut shells made by pyrolysis. Mixed feedstocks take the lowest relevant default.
Mistakes that cost credits
- Testing once a year when the feedstock changed mid-season.
- Lab reports with no batch number, so the verifier cannot tie a result to a tonne.
- Using a lab without accreditation or national approval.
What Senseible does here
On a Senseible project each batch holds its lab result, kiln sensor temperature logs and geotagged photos together, and the field app can record the lab sample and accreditation numbers for each batch.
Last reviewed 2026-11-02.