Laboratory-scale production of biofuel pellets from electron beam treated Scots pine (Pinus silvestris L.) sawdust

The effect of electron beam (EB) treatment on pine sawdust used as raw material for fuel pellets was studied. Dry sawdust was EB treated at different dosage levels up to 100 kGy. The effect of EB treatment on fatty and resin acid composition was studied for different dosage levels and compared to untreated sawdust. Pellets were pressed in a laboratory single pellet press unit according to a D-optimal, response surface modeling (RSM) experimental design, where sawdust moisture content and die temperature were varied independently for EB treatment dosages of 0, 18.2 and 48.9 kGy. The responses of the designed experiment were density and strength for the produced pellets. The results showed that the free fatty and resin acid content in the sawdust initially decreased with increasing EB doses but at the highest EB doses it increased. The total content of extractives however initially increased and then decreased with increasing EB dose. Pellets made of EB treated sawdust had a significantly (at 95% confidence level) higher density and compressive strength than pellets made from untreated sawdust. EB treated sawdust behaved similarly to stored (mature) sawdust as a pellet raw material. Thus, EB treatment opens the possibility for controlled ageing (maturation) of pellet raw materials.