Researchers have quantified the productivity and costs of mechanised coppice harvesting.
Coppice forests are often harvested using motor-manual systems. This is due to the poor form of trees (including multiple stems) and often tree size is small. However, increased labour costs and safety risks have necessitated the investigation of mechanised systems in the coppice forests, which are often used for biomass production. The feller bunchers designed for harvesting species such as beech, chestnut and oak, need to be more robust than the felling machines used for conventional pine and birch thinning in the Nordic countries.
The research was carried out in Italy, which is home to several manufacturers of feller-bunchers that claim to design heads specifically for this difficult coppice harvesting. Three different feller bunchers were tested, and each had a different felling attachment, namely a single-action shear, a double shear and disc saw. Trials were carried out in oak coppice, chestnut coppice, locust coppice, poplar coppice and single-stem short rotation coppice. The harvested volumes per hectare ranged from 57 to 130 dry tonnes per hectare (more than 130 to 300 m3 per hectare).
The productivity of the feller bunchers ranged from approximately 4.5 to 16 m3 per hour in multi-stem coppiced stands, and 39.4 m3 per hour in the single-stem stand. Even though the productivity levels in the coppice stands are lower than the single-stem stand and other productivity figures available for softwood thinning, they were still found to be acceptable considering the alternative harvesting methods. Costs ranged from Euro 1.47 to Euro 14.17 per m3. The shear heads produced poor cuts, with the single-action shears performing the worst. The disc saw achieved very low cuts and little damage. The research was titled “Mechanized coppice harvesting with new small-scale feller-bunchers: Results from harvesting trials with newly manufactured felling heads in Italy”. The research is currently in press in the Biomass and Bioenergy journal, and the authors are J Schweier, R Spinelli, N Magagnotti and G Becker. Source: http://www.sciencedirect.com/science/article/pii/S096195341400511X