The northern zone of Costa Rica has extensive forestry and agro-industrial development, which generates a large number of lignocellulosic residues that do not have an economic value but could represent a vast energy potential. Therefore, the objective of this study was to determine the optimal size and location of an electricity generation plant from the forest and agro-industrial biomass. The researchers worked with two forest species residues (Gmelina arborea and Tectona grandis) and two agro-industrial residues (Anana comosus and Saccharum o cinarum), representing the most extensive cultivations in the region. The material was characterized, then GIS layers of the species cultivation areas were analyzed and related to the roads and protected areas to de ne the twelve potential points where the power plant should be installed. Later the optimal supply radius of the plant and the optimal site conditions were determined. The study determined that the tree species have an average caloric power of 19059.50 kJ/kg, signi cantly higher than the agro-industrial ones (16684.9 kJ/kg). It was determined that 1,056,527.67 tons of dry biomass are generated per year, 6.5% of the biomass is arboreal, and 79.97% comes from A. comosus. Also, it was determined that the optimal supply radius for the plant is 30 km. Longer distances make the project nancially unviable. Considering this, the annual energy potential of the twelve points was evaluated, which varied from 4.06 to 101.82 MW. Point eleven was determined the best positioned by the biomass source and optimal environmental conditions for establishing the power plant.