Biochar Specifications: How to Read a Biochar Spec Sheet
A biochar spec sheet is where most purchasing mistakes start. This guide explains every parameter on a certificate of analysis, how it is measured, the limits set by EBC, WBC, IBI and the EU fertiliser rules, which values matter for each application, and the red flags that should stop a deal.
Two biochars can look identical in the bag and behave completely differently in a field, a concrete mix or an electric arc furnace. What separates them is on the specification sheet - and, more importantly, on the certificate of analysis (CoA) from an independent laboratory behind it. This guide explains every parameter you are likely to see, what it tells you, how it is measured, and which values matter for the job you are buying for.
It is written for buyers, and it is just as useful for producers who want to know what a serious buyer will check.
Spec sheet versus certificate of analysis
- A spec sheet (or product datasheet) is the producer's description of what they normally make: typical values or ranges. It is a sales document.
- A certificate of analysis is a laboratory report on a specific, sampled batch. It names the lab, the sample, the date and the test methods.
Buy on the CoA, not the spec sheet. A good CoA is from an accredited laboratory, is less than 12 months old, and comes from the same production line and feedstock as the material you are buying. If a quality certificate such as EBC or WBC is in place, the certification body arranges independent sampling at least once a year.
If you are new to biochar
Ask for the CoA before you ask for a price. A producer who can send a recent lab report for the exact product within a day usually runs a controlled process. One who can only send a generic datasheet usually does not.
Carbon and stability
Organic carbon (Corg) and total carbon
Total carbon (Ctot) is all the carbon in the sample. Part of it can be inorganic carbon - carbonates that sit in the ash, especially in biochar from straw, manure or other high-ash feedstock. Organic carbon (Corg) is total carbon minus that inorganic share, and it is the number that counts for stability, carbon removal and most quality classes. A lab report that only shows total carbon can overstate the useful carbon of a high-ash biochar, so ask for Corg.
Fixed carbon, volatile matter, ash and moisture (proximate analysis)
Proximate analysis heats a sample in steps and reports four fractions that add up to 100%:
- Moisture - water driven off at around 105 °C.
- Volatile matter (VM) - what escapes when the dry char is heated without air. High VM means pyrolysis was incomplete or too cool.
- Ash - the mineral residue left after burning.
- Fixed carbon (FC) - what remains, calculated as 100 minus the other three.
Fixed carbon and organic carbon are related but not the same: fixed carbon comes from heating behaviour, organic carbon from elemental analysis. Steel and energy buyers think in fixed carbon; soil and carbon-removal buyers think in organic carbon and H/Corg. Methods matter too - EBC and IBI measure ash at different temperatures, so compare like with like.
H/Corg and O/Corg - how stable is the carbon?
The molar ratio of hydrogen to organic carbon (H/Corg) is the standard lab proxy for how condensed, and therefore how stable, the carbon is. The lower the ratio, the more of the carbon sits in stable aromatic rings. Biochar standards require it to stay below 0.7, and the strictest classes ask for below 0.4. The O/Corg ratio (oxygen to organic carbon) is a second, supporting check that EBC and WBC say should stay below 0.4. Carbon removal methodologies use H/Corg to decide how much of the carbon they credit (see our guide to biochar carbon credits).
If you are new to biochar
If a supplier cannot give you H/Corg, you do not know whether you are buying biochar or partly charred biomass. It is the single most useful number on the sheet.
Physical and chemical properties
| Parameter | What it tells you | Typical units |
|---|---|---|
| Ash | Mineral content; high ash dilutes the carbon, adds alkalinity and can raise salinity | % of dry matter |
| Moisture / water content | How much water you pay freight on; dry biochar is dusty, very wet biochar can heat up | % of fresh mass |
| pH | Whether the biochar raises soil pH or affects cement setting | pH units (water or CaCl₂ extract) |
| Liming value | How much acidity the biochar neutralises, compared with lime | % CaCO₃ equivalent |
| Electrical conductivity (EC) / salt content | Soluble salts that can stress seedlings | mS/cm or g/kg |
| Bulk density | Volume per tonne - drives freight, storage and dosing | kg/m³ |
| Particle size distribution | Whether it handles, mixes and doses as intended | mm or µm, often as D10/D50/D90 |
| Specific surface area (BET) | Internal surface for adsorption - key for filtration, feed and remediation | m²/g |
| Water holding capacity | How much water the biochar itself can hold | % of dry weight |
| Nutrients (N, P, K, Ca, Mg) | What the biochar brings to the soil beyond carbon | % or g/kg of dry matter |
| Cation exchange capacity (CEC) | Ability to hold nutrients and bind metals | mEq/100 g |
Contaminants - what must stay low
- PAHs (polycyclic aromatic hydrocarbons) form during pyrolysis, especially when the gases are not cleanly separated from the char or when the process runs too cool. They are reported as the sum of 16 compounds (the US EPA list) and, increasingly, the sum of 8 (the EU food-safety EFSA list).
- Heavy metals - lead, cadmium, copper, nickel, mercury, zinc, chromium and arsenic - come from the feedstock, not the process. Clean wood gives clean biochar; contaminated waste wood or sludge does not.
- PCBs and dioxins/furans (PCDD/F) can form when the feedstock contains chlorine, for example from treated wood or plastics. Limits are tight, especially for feed and agriculture.
The standards side by side
Four sets of rules define what counts as good biochar. They are quality standards - they say what the material is and whether it is safe for a use. None of them, on its own, makes a carbon credit.
- European Biochar Certificate (EBC), run by Carbon Standards International (CSI). Version 10.5 (September 2025) has six classes, from strictest to most permissive: EBC-FeedPlus, EBC-AgroOrganic, EBC-Agro, EBC-Urban, EBC-Materials and EBC-Basic. EBC-Basic defines the minimum for a material to count as biochar at all. The former EBC-Feed class is being phased out: batches can still be certified under it until 31 December 2026. If you see EBC-ConsumerMaterials or EBC-BasicMaterials on an older certificate, those are the previous names of EBC-Materials and EBC-Basic.
- World Biochar Certificate (WBC), also run by CSI, for use outside the EU and EFTA. It drops the EU-specific legal requirements and has three classes: WBC-Premium, WBC-Agro and WBC-Material.
- IBI Biochar Standards (version 2.1, 2015) from the International Biochar Initiative, used mainly in North America. IBI and CSI announced in 2024 that the IBI standard will merge with the WBC.
- EU Fertilising Products Regulation, CMC 14 - the legal requirements for biochar ("pyrolysis and gasification materials") used in a CE-marked EU fertilising product, in force since July 2022. It also requires the material to be registered under REACH.
Carbon and stability
| EBC 10.5 | WBC 1.1 | IBI 2.1 | EU CMC 14 | |
|---|---|---|---|---|
| Minimum organic carbon | None - must be declared | None - must be declared | 10% (Class 1 ≥60%, Class 2 30-60%, Class 3 10-30%) | None |
| H/Corg (molar) | Below 0.7; below 0.4 for FeedPlus | Below 0.7; below 0.4 for Premium | 0.7 maximum | Below 0.7 |
| O/Corg (molar) | Should be below 0.4 | Should be below 0.4 | - | - |
Ash-rich biochars get special treatment. CMC 14 tests H/Corg on the ash-free fraction when organic carbon is below 50%, and since July 2026 CSI no longer applies the 0.7 limit to EBC biochars with less than 50% organic carbon and a solid-state electrical conductivity of at least 0.1 mS/cm. National rules can be stricter: Germany, for example, requires at least 80% carbon for biochar made from untreated wood.
PAHs and other organic contaminants (mg/kg dry matter)
| Sum of 16 EPA PAHs | Sum of 8 EFSA PAHs | PCBs | Dioxins/furans (PCDD/F) | |
|---|---|---|---|---|
| EBC-FeedPlus, AgroOrganic, Agro | 6.0 (±2.4 analytical tolerance) | 1.0 | 0.2 | 20 ng/kg I-TEQ |
| EBC-Urban, EBC-Materials | Declared | 1.0 | 0.2 | 20 ng/kg I-TEQ |
| EBC-Basic | Declared | 4.0 | 0.2 | 20 ng/kg I-TEQ |
| WBC-Premium | 6.0 (±2.4) | 1.0 | 0.2 | 20 ng/kg I-TEQ |
| WBC-Agro / WBC-Material | Declared | 1.0 / 4.0 | 0.2 | 20 ng/kg I-TEQ |
| IBI 2.1 | 6-300 (range, see below) | - | 0.2-1 | 17 ng/kg WHO-TEQ |
| EU CMC 14 | 6 | - | 0.8 (six indicator PCBs) | 20 ng/kg WHO-TEQ |
Under EBC 10.5, PCBs and dioxins only have to be tested when the 8 EFSA PAH sum is above 1 mg/kg. Two further PAHs (benzo[e]pyrene and benzo[j]fluoranthene) must each stay below 1 mg/kg in every EBC class. Feed-grade biochar (EBC-FeedPlus) has its own, much tighter dioxin and PCB limits based on EU feed law. Switzerland applies 4 ± 2 mg/kg for the 16 EPA PAHs to agricultural and feed classes sold there. IBI gives ranges rather than single limits: the biochar must meet the limit of the country where it is used, and the upper end of the range applies where there is none.
Heavy metals (mg/kg dry matter)
| Metal | EBC-FeedPlus* | EBC-AgroOrganic | EBC-Agro, Urban, Materials | WBC-Premium | WBC-Agro |
|---|---|---|---|---|---|
| Lead (Pb) | 5 | 45 | 120 | 120 | 300 |
| Cadmium (Cd) | 0.5 | 0.7 | 1.5 | 1.5 | 5 |
| Copper (Cu) | 70 | 70 | 100 | 140 | 200 |
| Nickel (Ni) | 25 | 25 | 50 | 50 | 100 |
| Mercury (Hg) | 0.1 | 0.4 | 1 | 1 | 2 |
| Zinc (Zn) | 200 | 200 | 400 | 420 | 1,000 |
| Chromium (Cr) | 70 | 70 | 90 | 100 | 200 |
| Arsenic (As) | 2 | 13 | 13 | 13 | 20 |
* EBC-FeedPlus values are at 88% dry matter, as in EU feed law. EBC-Basic and WBC-Material only require heavy metals to be declared. For copper and zinc, EBC allows higher values when the product is sold as a micronutrient fertiliser. CMC 14 sets no metal limits of its own; the limits for the final fertilising product come from the product categories of the EU regulation. IBI's ranges run from, for example, 121-300 mg/kg for lead and 1.4-39 mg/kg for cadmium.
How the numbers are measured
Two labs can report different values for the same biochar simply because they used different methods. These are the methods behind the European certificates (EBC 10.5, Annex 1):
| Parameter | Method |
|---|---|
| Carbon, hydrogen, nitrogen | ISO 29541 / DIN 51732 |
| Ash (at 550 °C) | ISO 1171 / DIN 51719 |
| Water content | ISO 589 / DIN 51718 |
| Carbonate (inorganic carbon) | ISO 925 / DIN 51726 |
| Volatile matter | ISO 562 / DIN 51720 |
| PAHs | DIN EN 17503 (toluene extraction) |
| pH | DIN ISO 10390 (in CaCl₂) |
| Specific surface area | DIN ISO 9277 (BET) |
| Bulk density | ISO 17828 |
IBI uses ASTM D1762-84 for moisture and ash (ash at a higher temperature than EBC) and US EPA methods for contaminants. In North America, the new ANSI/ASABE/USBI S668 standard (approved November 2025) brings biochar test methods together in one place.
Which parameters matter for each application
The right biochar for a steel plant is the wrong one for a greenhouse. Each of our buying guides has a full parameter table with targets and red flags; the short version:
| Application | Parameters that decide the purchase | Typical targets (from our buying guides) |
|---|---|---|
| Agriculture and soil amendment | H/Corg, PAH, heavy metals, EC, pH, particle size | H/Corg below 0.7; EC below 4 mS/cm for horticulture; pH 7-10 |
| Met-coal for steel | Fixed carbon, volatile matter, ash, sulphur, phosphorus, particle size | Fixed carbon 85-95%; ash below 6-10%; sulphur below 0.10%; phosphorus below 0.03% |
| Construction | Particle size, moisture, bulk density, water absorption, chlorides and sulphates | Moisture below 5% for concrete filler and below 2% for asphalt; tight particle size |
| Mine reclamation | pH and alkalinity, CEC, surface area, leachable metals | pH 8.5-10.5 for acid mine drainage; CEC above 50 mEq/100 g |
| Activated carbon | BET surface area, iodine number, ash, hardness | BET 800-1,400 m²/g for water treatment; iodine number 900-1,200 mg/g |
| Animal feed and bedding | PAH, dioxins, heavy metals, microbiology, particle size | EBC-FeedPlus limits for feed grade; dioxins below EU feed limits |
How to read a certificate of analysis
- Check the basis. Values are reported on dry matter (DM), fresh matter or dry ash-free basis. Comparing a 75% carbon figure on dry ash-free basis with 65% on dry matter is comparing nothing.
- Check the methods. The report should name the test standard for each parameter. Different ash or volatile matter methods give different numbers.
- Check the date and the batch. Older than 12 months, a different plant or a different feedstock - ask for a new one.
- Check the lab. It should be accredited for the methods it reports, and independent of the producer.
- Check the full contaminant panel. A CoA that reports carbon and ash but no PAHs or heavy metals is incomplete for any soil, feed or construction use.
Red flags
- Total carbon reported, but no organic carbon or H/Corg.
- No PAH result, or PAHs reported as a single number without the method.
- Volatile matter above about 20-30% for a product sold as biochar - a sign of incomplete pyrolysis.
- Ash above about 30-40% with no explanation - unusual unless the feedstock is manure, sludge or straw.
- The same CoA sent for several different products.
- A spec sheet with only "typical" values and no lab report behind it.
Questions to ask a supplier
- Can you send a certificate of analysis for this exact product, under 12 months old, from an independent accredited lab?
- What is the feedstock, and is it the same for every batch?
- What are the organic carbon content and H/Corg ratio?
- What are the PAH (16 EPA and 8 EFSA) and heavy metal results?
- On what basis (dry matter, fresh matter) are the values reported, and with which test methods?
- How much do the key parameters vary between batches?
- Is the product certified under EBC, WBC or another quality scheme - and if not, is it needed for my use?
- What particle size and moisture do you deliver, and can you hold them in a contract specification?
Next steps
BiocharLink lists producers from around the world, with their specifications and certifications. Compare suppliers on the biochar marketplace, go deeper with the buying guide for your application, or, if you produce biochar, list it for buyers. Interested in the carbon side? Read our guide to biochar carbon credits.
Thresholds as of October 2026. Sources: Carbon Standards International, European Biochar Certificate Standard 10.5E (15 September 2025) and "Exemption from H/Corg criterion for ash-rich biochars" (July 2026); World Biochar Certificate guidelines v1.1 (December 2024); International Biochar Initiative, Biochar Standards v2.1 (2015); Commission Delegated Regulation (EU) 2021/2088 (CMC 14); ANSI/ASABE/USBI S668 (2025).