Methodology and techniques for the appraisal of wood fuel balances in Sweden

The consumption of woody biomass for fuel has increased by 100% in 15 years. The current level is about 40 TWh per year and the total annual supply, excluding black liquor, is about 130 TWh per year. The rising demand for woody biomass for fuel purposes has made the need of a model for the calculation of the raw material base apparent. A model and a computer programme, “Biosims”, have been developed. Two different methods for woody biomass calculations are used in the model: 1) the regression estimate method, and 2) the ratio method. Both methods can be used at the stand level and at the regional level. The dry substance of woody biomass is calculated by using the biomass functions for the main domestic tree species (Pinus Silvestris, Picea Abies, Betula Pubescens, Betula Verrucosa). Volume of marketable timber is calculated by using the volume functions. Different assumptions, such as heat value and moisture content, can be programmed and various technical and ecological restrictions can be imposed. In the stand level method, diameter and height distributions are used for calculations. It is also possible to use the list of diameters for all trees in the stand or for utilized trees. The regional method works directly on a site represented by sample data and information from the National Forest Survey (NFS). These methods and the programme have been tested in several studies in Sweden. From the results of these studies it can be concluded that both methods provide satisfactory accuracy. The model can be used for energy planning at stand and at regional levels, and it can also be used by wood fuel producers as a tool for decision making.