ISO 17225-9:2021

Overview - ISO 17225-9:2021 (Solid biofuels - graded hog fuel & wood chips)

ISO 17225-9:2021 defines fuel specifications and quality classes for graded hog fuel and wood chips intended for industrial heat and power generation. It covers fuels produced from virgin wood, processing residues, used wood and blends (see ISO 17225-1 for raw‑material classification), and sets rules for particle size, property classes, sampling and declaration of quality. The standard is intended to support reliable trading, supplier–buyer communication and equipment compatibility for industrial biofuel use.

Key topics and technical requirements

• Scope and origins: Applies to hog fuel (irregular crushed pieces) and wood chips (sub‑rectangular chips ~5–50 mm) from specified raw materials (forest, processing by‑products, used wood, blends). Chemically treated used wood (1.3.2) is restricted to installations permitted to accept it.
• Property classes (I1–I4): Class I1 represents virgin and chemically untreated by‑products; I2–I4 allow progressively wider material origins including some chemically treated or used wood with corresponding restrictions and declarations.
• Particle size and fractions: Defined particle classes (P16, P31, P45, P63 and PL10–PL30+) with main/coarse/fines fractions determined by sieving (ISO 17827‑1). Fines classes (F02–F30+) set maximum percentages of <3.15 mm material.
• Physical and chemical properties: Requirements reference standard test methods for moisture (ISO 18134), ash (ISO 18122), calorific value (ISO 18125), elemental and minor elements (ISO 16948, ISO 16968, ISO 16994), bulk density and heavy extraneous material (ISO 19743).
• Contamination limits: Heavy metals and halogenated organic compounds in certain raw‑material classes must not exceed virgin wood or country‑typical levels. Producers must declare origin and chemical treatment status.
• Sampling, analysis and declaration: Sampling (ISO 18135 or ISO 21945), sample preparation (ISO 14780) and declared quality are mandatory; delivery lot averages must meet declared limits.

Practical applications and typical users

• Industrial users: Power plants, combined heat and power (CHP) facilities and large boilers using hog fuel or wood chips for thermal energy.
• Fuel suppliers and traders: Standardizes product descriptions for contracts, marketing and quality assurance.
• Equipment manufacturers and operators: Ensures feed, handling and combustion systems are compatible with defined particle sizes and contamination levels.
• Regulators and procurement teams: Supports permitting, environmental reporting and specification of acceptable feedstocks.

Related standards

• ISO 17225‑1 (general requirements and raw‑material classification)
• ISO 17827‑1 (particle size distribution)
• ISO 18135 / ISO 21945 (sampling)
• ISO 14780 (sample preparation)
• ISO 18134, ISO 18122, ISO 18125, ISO 16948, ISO 16968, ISO 16994, ISO 19743 (analytical methods and properties)

Using ISO 17225-9:2021 helps ensure consistent fuel quality, safer combustion, predictable emissions and smoother commercial transactions for industrial solid biofuels such as graded hog fuel and wood chips.