Productivity and Profitability of Forest Machines in the Harvesting of Normal and Overgrown Willow Plantations

Abstract

Forage harvesters used in Short Rotation Willow Coppice (SRWC) plantations in Sweden suffer from an inability to efficiently harvest stems thicker than 6 – 7 cm at stump height. An alternative, when harvesting in such plantations, might be to use forest machines fitted with accumulating felling heads. This study aimed to measure the time consumption and to compare the costs of two forest machine systems in a normal (N) and an overgrown (O) SRWC, where the respective biomass densities were 36 and 56 Oven-Dry tones (OD t) per ha. The first machine system included a harvester and a forwarder and the second consisted of a harwarder (one-machine system).When harvesting and forwarding the biomass for 250 m, the productivity of the two and one-machine system was on average 2.3 (sd = 0.6) and 0.9 (sd = 0.2) OD t/Productive Work hour, respectively. Biomass density or stem sizes had a marginal effect on the time consumption per hectare for the two-machine system, but were significant for the one-machine system. The productivity for the two-machine and one-machine system in the O area, compared to the N area, was 40%and 36%higher, respectively. The net income was positive when using the harvester–forwarder system but it was negative for the harwarder. Increases in biomass density or stem sizes increased the profitability of themachine systems studied. Thus, if dealing with more overgrown plantations than those studied, forest machines, and especially a harvester-forwarder system, may offer an efficient and economical alternative to conventional forage harvesters.