ISO 17225-7:2021

Overview

ISO 17225-7:2021 - Solid biofuels - Fuel specifications and classes - Part 7: Graded non-woody briquettes defines fuel quality classes and technical specifications for non-woody briquettes made from herbaceous, fruit, aquatic biomass or their blends. It supports consistent trade, safe use and communication between producers, buyers and appliance manufacturers. Thermally treated briquettes (e.g. torrefied) are excluded.

Keywords: ISO 17225-7, non-woody briquettes, solid biofuels, fuel specifications, biomass briquettes, biofuel standards.

Key topics and requirements

The standard specifies classification, declaration and test methods for graded non-woody briquettes. Major technical requirements include:

• Covered raw materials: herbaceous biomass, fruit biomass, aquatic biomass, and biomass blends/mixtures (see ISO 17225‑1 for origin codes).
• Fuel quality classes: A1, A2 and B (A1 recommended for residential use; blending with woody biomass is recommended to reach A1 limits).
• Physical and chemical limits (selected, dry or as‑received units as stated in the standard):
  • Moisture: A1/A2 ≤ 12% (wet basis); B ≤ 15%.
  • Ash (dry basis): A1 ≤ 3%; A2 ≤ 6%; B ≤ 10%.
  • Particle density (as received): A1/A2 ≥ 0.9 g/cm3; B ≥ 0.6 g/cm3.
  • Net calorific value: ≥ 14.5 MJ/kg (≈4.0 kWh/kg).
  • Nitrogen (dry): A1/A2 ≤ 1.5%; B ≤ 2.0%.
  • Sulfur (dry): A1/A2 ≤ 0.20%; B ≤ 0.30%.
  • Chlorine (dry): A1 ≤ 0.10%; A2 ≤ 0.20%; B ≤ 0.30%.
  • Heavy metals (dry basis): limits for As, Cd, Cr, Cu, Pb, Hg, Ni, Zn are specified (e.g., As ≤ 1.0 mg/kg for A1/A2, ≤ 1.5 mg/kg for B; Hg ≤ 0.1 mg/kg).
• Additives: maximum 5% (mass) and type/amount must be stated (pressing aids, inhibitors, starch, oils etc.).
• Dimensions & shape: briquette geometry (diameter, length, width, height) must be declared.
• Informative properties: ash melting behaviour (SST, DT, HT, FT) and surface area should be stated where relevant because non-woody fuels often produce low‑melting, corrosive ashes.

Practical applications and users

ISO 17225-7 is intended for:

• Fuel producers and suppliers declaring product quality.
• Appliance manufacturers (stoves, boilers, room heaters) that require clear fuel specs for design and warranty.
• Heating system installers, facility managers and specifiers selecting briquettes for residential, small commercial, public building and industrial applications.
• Regulators and procurement teams ensuring safe combustion results and reduced corrosion, fouling or emissions.

Practical guidance in the standard emphasizes appropriate sampling, analysis and documentation so users can manage risks associated with high ash, chlorine and alkali contents typical of non-woody biomass.

Related standards

• ISO 17225-1:2021 (General requirements and origin codes)
• Sampling & analysis: ISO 18135, ISO 21945, ISO 14780, ISO 18134-1/2, ISO 18122, ISO 18125, ISO 16948, ISO 16968, ISO 16994, ISO 18847

Using ISO 17225-7 together with ISO 17225-1 and the referenced test standards ensures consistent, market-ready specifications for non-woody biomass briquettes.