Bioenergy is expected to become one of the key energy resources for global sustainable development. However, bioenergy cannot be infinite, because the land area available for biomass production is limited and a certain amount of biomass must be reserved for food and materials. The purpose of this study is to evaluate global bioenergy potential: for this purpose, the authors developed a global land-use and energy model (GLUE) formulated using a SD (System Dynamics) technique. Through a simulation, the following results were obtained. (1) There will be a certain potential for energy crops harvested from surplus arable land in the developed regions of the world. However, care must be taken because the potential is sensitive to the global food supply and demand. (2) There will be a large bioenergy potential for biomass residues, such as cereal-harvesting residues, animal dung, roundwood felling residues, and timber scrap. The ultimate bioenergy potential, from all the biomass residues, will be 277 EJ/yr in A.D. 2100 in the world. (3) The mature-forest area in the developing regions decreases from 2.1 billion ha in 1990 to 0.8 billion ha in 2100, although it is assumed that the felling area is reforested completely after A.D. 2025. Thus, there will not be much room to obtain more fuelwood from forests in the developing regions.