Characterisation of sawdust-like wood materials

The aim of this study was to examine the chemical and morphological properties of sawdust-type wood materials and compare them with conventional wood chips. Wood sawdust and chip screenings were air-dried and fractionated. Fibre dimensions, inorganics, bark, extractives and lignin were determined for the different fractions. Wood chips were also studied similarly for reference purposes. Carbohydrate content was further determined from the smallest size fractions and the largest size and weight fractions. We found that the particle size of sawdust-like wood material was not uniform and the distribution was concentrated in the smallest fractions containing short fibres and narrow cell walls. On the other hand, fibre width was almost intact resulting in larger lumina than corresponding chips. Bark particles, sand and grit were accumulated in small fractions, chip screenings containing more inorganics, extractives, lignin and bark than sawdust. Finally, the fractionation process did not affect the wood fibre chemistry, only small differences were observed when comparing the carbohydrate content between the different fractions in the same wood raw material. We suggest that sawdust-like wood materials are valuable sources for producing different chemical and mechanical pulps which can be used in paper formulations based in mixtures of short and long fibres.