Evaluating the production cost and quality of feedstock produced by a sawdust machine

The utilization of forest residues as a woody biomass feedstock for the production of bioenergy and bioproducts requires processing (i.e., comminution) to meet feedstock specifications, such as moisture content and particle size. The objective of this study was to determine the effect of small diameter processed hardwood (SH) and small and large diameter processed softwood (SS and LS) stems had on the productivity and cost of a track mounted sawdust machine that produced sawdust. In addition, moisture content, particle size distribution, bulk density, and the effect of knife wear were evaluated. The sawdust machine's 298-kW engine was capable of comminuting all material types except the LH stems. The machine's productivity ranged between 18.3 and 26.7 bone-dry metric ton (BDmT)/productive machine hour (PMH) at a cost of US $5.3 and US $3.6/BDmT, respectively. The moisture content of material used in the study ranged between 26 and 36%. The geometric mean particle lengths for SH, SS, and LS were 4.7, 5.3, and 4.4 mm, respectively. The machine could not process LH materials due to limited power. The bulk density of feedstock produced ranged between 234 and 281 kg/m³. Analysis indicated that knife wear did not have a significant effect on comminution productivity and feedstock quality while comminuting 60 green metric tons (GmT) of forest residues. The results from this study suggest that this sawdust machine can be useful in producing feedstock for new biomass conversion technologies that require small, uniform particles.