Contaminants and Quality
Hub for environmental contaminants and product-quality framing of biochar: PAHs, heavy metals/ash, PFAS—including whole-process transfer/destruction and soil immobilization—and the testing stack (EBC / IBI / ANSI S668). Not a carbon-credit methodology. Report context: 2026-09-16.
Companion chapters (2026-09-16): PAHs · Heavy Metals and Ash · PFAS · Testing EBC IBI S668. This note is the spine—risk map, standards roles, and practice takeaway.
Related notes: Properties · Production · Biochar Quality from Process · Product Standards EBC IBI · standardizes biochar lab testing · MRV Stack · Risks and Controversies · Production Hub · Key Sources
1. Why quality control matters
Biochar’s climate and soil value collapses if products introduce PAHs, heavy metals, dioxins/PCBs, or PFAS into soils, feed, or materials beyond regulatory and certification limits. Consensus in the science report and EBC practice: clean process design + batch testing against recognized limits (EBC; IBI; science report §3.4). Market-side safeguards also appear in MRV Stack and Risks and Controversies.
2. Contaminant map
| Class | Primary driver | Deep chapter |
|---|---|---|
| PAHs | Vapor condensation / process design (feedstock secondary) | PAHs |
| Heavy metals & ash | Feedstock load + mass-loss concentration; Hg volatilizes | Heavy Metals and Ash |
| PCBs / PCDD/F | Contaminated feeds + vapor pathway; EBC triggers on high PAH | PAHs · Testing EBC IBI S668 |
| PFAS | Biosolids, coated paper/compost, and impacted wastes; distinguish char removal, phase transfer, and destruction | PFAS |
| Salts / EC | Manure/ash-rich chars | Heavy Metals and Ash · Properties |
3. Standards layers (do not confuse)
| Layer | Examples | Role |
|---|---|---|
| Product standards | EBC / IBI | Pass/fail material classes, H/C_org, contaminant limits |
| Test methods (U.S.) | standardizes biochar lab testing · PDF | How to measure (incl. PFAS EPA 1633A)—not pass/fail by itself |
| Carbon methodologies | Verra / Puro / Isometric / CSI | May require EBC/IBI or equivalent characterization |
| Farm practice | NRCS soil carbon amendment in US ag | Eligibility, not tradable credits |
CSI Global Biochar C-Sink requires EBC- or WBC-certified biochar—see CSI Global Biochar C-Sink. Detail: Testing EBC IBI S668 · Product Standards EBC IBI.
4. Elemental-ratio quality gates (reminder)
- H/C_org ≤ 0.7 (EBC/IBI/IUPAC biochar definition); FeedPlus / manure < 0.4 (EBC 10.5E; IUPAC biochar terminology · DOI)
- O/C_org often / should be ≤ 0.4 (Properties · H-Corg and O-Corg)
These are quality/definition gates; permanence factors are separate (Permanence).
5. Headline EBC contaminant numbers (v10.5E)
From EBC Guidelines 10.5E (14 Aug 2025):
| Parameter | FeedPlus / Agro / AgroOrganic (indicative) | Notes |
|---|---|---|
| Σ16 EPA PAH | 6.0 ± 2.4 mg kg⁻¹ DM | Analytical accuracy caveat in EBC text |
| Σ8 EFSA PAH | 1.0 mg kg⁻¹ DM (also Urban/Materials) | Basic allows 4 mg kg⁻¹ Σ8 |
| Heavy metals | Class-specific Table 2 (Pb, Cd, Cu, Ni, Hg, Zn, Cr, As) | Basic: declaration only |
| PCB / PCDD/F | Triggered if Σ8 EFSA PAH > 1 mg kg⁻¹ | Limits 0.2 mg kg⁻¹ PCB; 20 ng kg⁻¹ I-TEQ PCDD/F |
Full discussion: PAHs · Heavy Metals and Ash · Testing EBC IBI S668.
6. Practice takeaway
- Design reactors for vapor–char separation before cooling; then test every batch.
- Match certification class to end use (feed ≠ materials ≠ basic industrial).
- For biosolids, coated-paper/compost, or impacted-waste routes, budget metals + PFAS analytics and whole-train sampling up front (PFAS).
- Use S668/EPA methods in North America; EBC-endorsed labs for EBC PAH methods (matrix matters).
Primary links
- EBC Guidelines PDF · EBC home
- IBI Biochar Standards
- ANSI S668 PDF · standardizes biochar lab testing
- Bilias et al. 2024 IUPAC · IUPAC biochar terminology