Waste sawdust: problem or profit?
WASTE SAWDUST has been the curse of Australian sawmillers for over a century.
What to do with it? Remember the old Olivine burners? Those conical structures dotted around the countryside pumping out smoke from the burning wet sawdust inside. Well, now there’s a viable solution to convert waste sawdust into profitable fuel pellets.
The first step is to dry the material. It needs to be around 11% moisture content (m.c.) to convert into pellets. There are a couple of ways to do this. Use a drum drier or belt drier coupled to a waste wood burner. The boiler runs on a combination of the wet AND dried fuel to have an average m.c. boiler fuel of about 30%. (roughly 50/50 wet/dry by volume) Hot air from the boiler is then pumped through the drier driving off moisture from the wet biomass. The final m.c. is a function of the dwell time in the drier and drying temperature.
Both sawdust and wood chips can be dried. Drying systems start at around 500kg / hr and go up to 2000kg / hr. Dry product is removed pneumatically – or via conveyor screw – and stored ready for use. Dry wood chip is in demand from manufacturers with biomass boilers because the dry material burns cleaner than wet woodchip and therefore less emissions from the smoke stack. (And more revenue from dry chip sales)
Further processing can include converting the dried biomass into fuel pellets. Small pellet plants start at 120kg / hr and cost around $120,000 (for a complete system including shredder, silo, hammermill, pellet press, vibrating screen, storage silo and bagging line) and range up to several Tonnes / hr. However, in the sub 1000kg/ hr range there are 100, 200, 400, 500, 800 kg / hr complete turnkey systems available. With the growth of pellet heaters exploding consumers are now looking for local fuel pellet supplies close to where they live.
Nova N-Plus 1000kg per hour.
Die: Ring die and rollers from a Nova pellet press.