This paper presents an approach to perform geo-referenced estimations of forest wood residues availability for energy use based on forest inventory data integration into a GIS. Three different estimation methods are described. The first one evaluates biomass availability based on the application of biomass expansion factors to stem volume data of the forest inventories. The method accounts for forest dynamics and assigns management treatments in function of forest properties. The second method estimates available forest wood residues applying biomass production by tree, derived from field studies, to the inventoried tree species. The third method links inventory data with national statistics of final cuttings of commercial tree species. Useful biomass potential is then estimated based on ecological, logistic and economic constraints. The methods were tested in a case study in Northern Spain where optimal facilities location based on marginal delivery costs and resources competition between facilities were found. Results are presented for three different scenarios. Biomass resources estimations under the different methods result in significant differences. GIS maps of useful biomass availability estimations are presented giving an idea of the optimal locations for bioenergy facilities based on resource availability.