Overview - EN ISO 17225-2:2021 (Graded wood pellets)
EN ISO 17225-2:2021 (CEN adoption of ISO 17225-2:2021) is the international/European standard that defines fuel specifications and quality classes for graded wood pellets used as solid biofuels. It applies to pellets produced from:
- forest, plantation and other virgin wood (1.1),
- by‑products and residues from the wood‑processing industry (1.2), and
- chemically untreated used wood (1.3.1).
Thermally treated biomass pellets (e.g., torrefied pellets) are explicitly excluded. The document supersedes the 2014 edition and aligns classification principles for trading, appliance compatibility and regulatory reporting.
Key topics and technical requirements
This standard focuses on measurable pellet quality attributes and the procedures to determine them. Main technical topics include:
- Fuel quality classes (e.g., A1, A2, I1, I2): defined to match end‑use requirements (A‑classes for higher‑quality residential/commercial use; I‑classes for industrial use).
- Physical properties: pellet diameter, length, bulk density, particle density (informative), coarse pellet fines (informative), and mechanical durability.
- Chemical and combustion properties: moisture, ash content, calorific value, elemental contents (C, H, N, S, Cl), and ash melting behaviour (now normative with threshold DT values).
- Sampling, sample preparation and test methods: references to established ISO test methods (e.g., ISO 18135 sampling, ISO 14780 sample preparation, ISO 18134 moisture, ISO 18125 ash, ISO 18125/18122 calorific/ash tests, ISO 21404 ash melting).
- Specification tables: class limits are provided in tabular form (refer to the standard for numerical thresholds).
Applications and who uses the standard
EN ISO 17225-2:2021 is practical for:
- Pellet manufacturers - to certify product quality and meet buyer specifications.
- Fuel traders and procurement teams - to specify, compare and procure graded wood pellets with confidence.
- Heating appliance and boiler manufacturers - to design and recommend compatible pellet quality classes for stoves, burners and boilers.
- Test laboratories and conformity assessors - to perform standardized sampling and analytical testing.
- Regulators and project owners - for permitting, reporting and ensuring safe, low‑emission operation in residential, commercial and industrial installations.
Practical benefits include improved market transparency, reduced installation/operator problems, and better alignment between pellet quality and appliance performance.
Related standards
For exact class limits, test procedures and normative tables, consult the full EN ISO 17225-2:2021 publication.