The productivity and cost of harvesting whole trees from early thinnings with a felling head designed for continuous cutting and accumulation

Abstract

The main problem with the utilization of untended stands for energy use is that small-diameter trees are expensive to harvest, and the value of the harvest fails to exceed the harvesting cost. Until now, the equation has appeared difficult to solve, but a wood harvesting innovation–the Risupeto II accumulating felling head–which works on a continuous basis, could provide a solution to the harvesting cost problem of young stands with a dense undergrowth. The novel accumulating felling head is attached to the boom of the crawler excavator, and trees are harvested at full-tree length. The crosscutting is done later during loading by a forwarder equipped with a grapple saw. The objectives of the present study were: 1) to define the productivity; 2) produce time consumption models for the Risupeto II harvesting unit in selective thinnings and 3) to determine the harvesting cost of whole trees from the early thinnings based on the above described two-machine configuration. Time study data from the 16 study plots consisted of 3,099 whole trees where the average tree volume varied between 14.2 and 52.0 dm3 resulting in 73 m3 of whole trees. The productivity varied between 11.2 and 26.6 m3/PMh on the time study plots indicating that felling-bunching productivity was relatively high compared to the latest studies with the Nordic harvesting technology in early thinning. According to the profitability analysis, the harvesting costs could be covered by the revenue from energy wood sales.