Evaluation of work methods for production of solid biofuel from harvesting residues in commercial thinning of coniferous forests

Abstract

The scope of the study is the development and validation of a working method for the production of solid biofuel from harvesting residues in the commercial thinning before the final felling, including the elaboration of recommendations for arranging of harvesting residues and round-wood logs between the remaining trees. According to the study results, biofuel production in commercial thinning does not impair the productivity of the harvesting and forwarding, but it is necessary to take into account the possible additional working time consumption to move harvesting residues into strip-roads, if the ground bearing conditions would significantly deteriorate before forwarding. The recommended method of biofuel production from harvesting residues considers felling of trees growing on the strip-road at approximately 45-90 degree angles to the direction of movement of the harvester. After felling trees on the strip-roads, harvesting on harvesting sectors should be designed in perpendicular to the direction of movement of the harvester. The sector shall be divided into 2 zones. The first zone is up to 6 m from the longitudinal axis of the strip-roads. The trees in the 1st zone are felled in the direction of the strip-road, planning to leave the logging residues on the strip-roads, whereas in the 2nd the trees are felled from themselves and logging residues are piled between roundwood logs. Depending on the overgrowth of the strip-roads, using this method, the share of logging residues available for the biofuel production will be 30-50 % of the total quantity of logging residues. In total 424 m3 (120-160 m3 per method) of roundwood assortments were produced during the time studies, the estimated amount of harvesting residues produced during the trial is 18 m3 in average per method.