6mm vs 8mm Pellets: Which Diameter Fits Your Burner
Choosing between 6mm and 8mm pellets: feed auger compatibility, combustion behaviour, fines generation, availability, and price differences explained.
Diameter is the first thing a pellet buyer specifies and the easiest thing to get wrong. The rule of thumb: 6 mm for anything domestic, 8 mm for anything industrial — but the reasoning matters when your equipment sits near the boundary.
Feed system
Small stove augers and pneumatic delivery hoses are engineered for 6 mm. Feeding 8 mm through them raises bridging and jamming risk. Industrial screw conveyors and chain drags handle 8 mm without issue and actually suffer less abrasion.
Combustion
- 6 mm: faster ignition, quicker load response, suits modulating domestic boilers
- 8 mm: slower, steadier burn, suits large grate and fluidised-bed units
- Both deliver the same calorific value per kg at equal moisture
Fines and handling
Per tonne handled, 8 mm generates fewer fines than 6 mm because there is less surface area to abrade. Over a 20,000 t cargo with four transfer points, that difference is measurable at discharge.
Price and availability
8 mm is typically slightly cheaper per tonne: the die wears more slowly, throughput per mill hour is higher, and the grades that use 8 mm allow broader feedstock. 6 mm A1 carries the premium.
Still unsure
Check the boiler manual for the stated fuel standard. If it cites ENplus A1 6 mm, do not substitute. If it cites ISO 17225-4 or simply "wood pellets 6–8 mm", 8 mm is the economic choice.
Pellet Industries ships ENplus A1 and industrial biomass pellets worldwide in 15 kg bags, big-bags, and bulk vessel loads.
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