Cost and productivity for processing and sorting forest residues

Biomass conversion technologies such as biochar, torrefaction, and briquetting have the potentials to increase the economic value of forest residues, however requires high quality feedstocks. The goal of this study was to evaluate the cost associated with processing and sorting forest residues in order to reduce feedstock contamination and facilitate comminution operations in an effort to control particle size. Three harvest units selected were further divided into three sub-units. One of three treatments, no sorting, moderate sorting and intensive sorting, were carried out for each sub-unit by the sawlog processor. For the sorted treatment units, the processed tree tops were sorted into conifer and hardwood piles. The remaining slash, consisting of chunks, branches, etc., generated during sawlog processing were piled separately. The sorting treatments varied the intensity in which residues were processed and sorted. Results showed that the total operational costs (stump to truck) were similar between sorting and not-sorting. A standardized comparison showed a cost range of $97 to 106/MBF for sawlogs harvested. The productivity of the processor sorting the forest residue showed a gradual increment in cost of around $ 2/MBF from non- sorting to the intensive sorting. Our results show that a majority of the cost was in forwarding for all treatment therefore additional processing cost to sort forest residues did not have an impact on total cost between treatments. Analysis done to predict the tops to slash ratio showed that 19-25 % of the total forest residues generated were tree-tops.