Biomass has enormous potential globally, but it requires sustainable management and conversion into modern bioenergy that aligns with the Sustainable Development Goals (SDGs). This study assesses sustainable biomass potential for energy generation in South America, considering forestry, agriculture, agro-industrial, and municipal solid waste biomass. The Autoregressive Integrated Moving Average (ARIMA) time series forecasting model with data from the Food and Agriculture Organization Corporate Statistical Database (FAOSTAT) and the World Bank up to 2050 is used. In 2021, the total biomass theoretical potential amounts to 1214 million tonnes (Mt), projected to increase to 1371 Mt by 2050. The available technical potential for energy purposes ranges from 796 Mt in 2021 to 916 Mt by 2050, with approximately 66 % attributed to agricultural biomass, 10 % to agro-industrial biomass, 17 % to forestry biomass, and 7 % to municipal waste biomass. Notably, not all countries experience growth in bioenergy potential from 2021 to 2050. Increasing forestry biomass recoverability from 25 % to 75 % enhances the total technical potential by 7 % for 2050. Primary bioenergy potential, utilizing available biomass, ranges from 13,831–15,892 PJ between 2021 and 2050, equivalent to 1278 to 1444 Terawatt hour (TWhe) when considering biomass conversion to electric energy. The share of bioelectricity could be 24 % of the total electricity generation in 2021. Additionally, modern bioenergy could help achieve sustainable development goals and decarbonize the energy sector in the region. This assessment of modern bioenergy potential in South America is relevant for subsequent techno-economic and environmental evaluations towards global energy decarbonization by 2050.