ISO 17225-2 defines industrial wood pellet grades A1, A2, and B — but in practice, most transactions reference a subset of parameters that matter to the specific buyer. This guide walks through each key parameter, what it means commercially, and what to negotiate.
Wood pellets are the most standardized of all traded biomass fuels. ISO 17225-2 defines three industrial grades (A1, A2, B) and two residential grades (I1, I2) by a set of physical and chemical parameters. In practice, most international utility and co-firing plant contracts reference a subset of these parameters — the ones that actually affect boiler performance, operations cost, and regulatory compliance.
The Parameters That Actually Get Negotiated
| Parameter | Why Buyers Care | Typical Range (Malaysian rubber wood) | Hard Limit |
|---|---|---|---|
| GCV (ADB) | Core energy content — determines price/GJ | 17.5–19.5 MJ/kg | ≥16.5 MJ/kg ISO A2 |
| Moisture (ARB) | Reduces as-received energy; shipping cost/GJ | 8–12% | ≤10% (A1), ≤12% (A2) |
| Ash (%) | Boiler maintenance, slagging, disposal cost | 0.8–2.5% | ≤1.5% (A1), ≤3.0% (A2) |
| Chlorine (%) | Superheater corrosion — critical for high-temp boilers | <0.05% | ≤0.02% (A1), ≤0.03% (A2) |
| Sulphur (%) | SO₂ emissions, environmental compliance | <0.04% | ≤0.04% (all grades) |
| Mechanical durability | Pellet breakage during handling/shipping | >97% | ≥97.5% (A1) |
| Bulk density | Shipping economics (GJ/container) | 580–650 kg/m³ | ≥600 kg/m³ (A1) |
Basis Risk: ADB vs ARB
The single most common source of commercial dispute in biomass contracts is misalignment between ADB (Air Dried Basis — the lab-certified number) and ARB (As Received Basis — the field condition). A pellet certified at 10% moisture ADB may arrive at 13–16% ARB after ocean shipping in humid conditions. Always specify which basis applies at inspection, at load port, and at discharge port. FuelCore recommends using ARB at discharge port as the commercial basis for energy-content-linked price adjustments.