Roundwood and bioenergy production from forestry : environmental impact assessment considering different logging systems

The aim of this paper is to analyse the environmental performances of three different extraction systems for forestry considering three different scenarios concerning the valorisation of forest residuals are analysed. The compared tree extraction systems are characterised by felling and processing performed with chainsaw and three different extraction methods: i) by farm tractor equipped with a winch; ii) by skidder and iii) by cable crane. The “Full Tree System” was adopted for all the felling sites; trees were felled and transported to roadside with branches and top intact. For wood chips produced from branches and tops, different scenarios were considered: heat and electricity generation and substitution of wood-chip production. To evaluate the environmental performance the Life Cycle Assessment (LCA) approach was applied. The selected functional unit (FU) is 1 m3 of roundwood; the system boundary involves all the operations carried out in forestry (felling, bunching, extraction, processing, chipping of forest residuals), the transport of the produced wood chips and all the related inputs and emissions. A comparison with previously carried out studies in similar geographic areas were performed. The study's outcomes show how, the environmental results among the different logging systems are not univocal and the best logging system depends on the considered impact category. Though cable yarder is recognised as an extraction method able of reducing the physical impacts on residual stand (wounding) and soil (disturbance and compaction), for 10 of the 12 impact categories evaluated in this study, achieves the worst performances. The logging systems in which the extraction is performed using the tractor and the skidder show the best performance for 6 of the 12 evaluated impact categories. Finally, regarding wood residues utilisation and the impact of particulate matter formation, the energetic valorisation of wood chips does not involve any benefit but involves a worsening of the environmental performances due to wood combustion emissions.