Pellet Moisture Content: Why 8–10% Matters in Contracts
Pellet moisture content drives calorific value, durability, storage safety and price. Where the limits sit and how to write moisture clauses into contracts.
Moisture is the one parameter that changes after the pellet leaves the factory. That makes it the most disputed line in any pellet contract.
The physics
Water in fuel absorbs energy to evaporate before combustion begins. Going from 8 % to 12 % moisture cuts usable energy per tonne by roughly 6–7 % and lowers flame temperature, which raises unburnt carbon in the ash.
Standard limits
- ENplus A1 / A2: ≤ 10 % as received
- ISO 17225-4 industrial: ≤ 12 % typical
- Factory gate target for good producers: 6–8 %
What raises moisture in transit
Uncovered truck beds, condensation in unventilated containers, rain during barge transfer, and floor storage without a vapour barrier. Pellets are hygroscopic — they pull moisture out of humid air continuously.
Structural consequence
Above roughly 15 % moisture the lignin bond softens and pellets swell then crumble. That damage is irreversible; drying wet pellets does not restore them.
Contract language
Specify: maximum moisture, the testing standard (EN ISO 18134), the determination point, the sampling method, and a price adjustment or rejection threshold. Ambiguity here is how claims turn into arbitration.
Our contracts default to ≤ 8 % at load port with independent inspection, and we publish the certificate before vessel departure.
Pellet Industries ships ENplus A1 and industrial biomass pellets worldwide in 15 kg bags, big-bags, and bulk vessel loads.
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