Waste saw­dust: prob­lem or profit?

Australian Forests and Timber - - RECYCLING - By Tony Es­plin

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.

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