Currently, developing new or more efficient ways of producing bioenergy has caused governments from around the world to formulate compromises. These compromises translate, on a national scale, into government policies and strategies that aim to decarbonize the energy matrix of each country. The first step for efficient development is the quantification and energy-potential characterization of the available biomass. Using this framework, this study establishes the energy potential of the residual biomass produced by agricultural, agro-industrial, and forestry processes in Colombia, with gasification being the selected transformation technology. For this purpose, data from primary and secondary sources were analyzed. Next, some biomasses were prioritized according to their availability and physicochemical properties. Then, the theoretical energy potential of the total biomass produced in these productive sectors was estimated by using its physicochemical properties. The technical biomass–energy potential of the country (204.8–235.3 PJ) was estimated by considering the current level of unused biomass and evaluating the logistics and conditioning requirements of the gasification process, while accounting for the peaks and off-peaks of production in the country. Thus, if all the biomasses were processed in a gasification plant (22.2–24.0% efficiency), as proposed in this study, then the installed capacity—if the plant-use factor was 85%—would range between 1696.7–2111.3 MW. The results of the present research were validated by representatives of unions, companies, and government entities.