Effects of intensive forest management on net climate impact of energy biomass utilisation from final felling of Norway spruce

The main objective of this work was to study the effects of intensive forest management on net climate impact of energy biomass (logging residues and/or stumps and coarse roots) utilisation from final felling of Norway spruce (Picea abies L. Karst) grown on medium-fertile site under boreal conditions in Finland. We employed forest ecosystem model simulations and a life cycle assessment (LCA) tool to calculate net CO2 exchange for utilising biomass in biosystem and coal in fossil system. In the biosystem, baseline management (business as usual, BT) and management with maintaining 30% higher stocking in thinning than in the BT regime were used. In addition, nitrogen fertilisation and improved planting material both alone and as combined were used to enhance growth in order to assess effects of intensive management on net climate impact. Carbon neutrality of biomass utilisation under alternative management was compared with the utilisation of coal. We found that the carbon neutrality of biomass utilisation varied between 0.5 and 3.4 (i.e. from partial to full neutrality), depending on the management applied. Under intensified management, CO2 emissions associated with energy biomass utilisation could be offset by forest ecosystem carbon sequestration over the following 20 years. Under the BT regime, such compensation could not be fully achieved over the rotation, but the utilisation of biomass produced less emissions per unit of energy than the use of coal. From a climate change mitigation point of view, the intensive management of Norway spruce could increase the climate benefits of energy biomass utilisation.