Considering the actual state of global needs for all forms of energy, assessing the potential of organic wastes that could be processed to obtain biogas, is one of the main tasks for region’s successful socio-economical development. Using currently available data in integrated deterministic modeling approach allows assessing of total biomass availability. Based on literature and on feedback from farmers (their current local practices) and current uses of by-products local models were developed to evaluate the use of agricultural and waste products and to calculate the feedstock availability for biogas production in each region. To evaluate the biomass potential, different data sources were used, e.g., EUROSTAT data were used for assessment of land use, agricultural production yields, population and tourism potential, as well as national statistics were used for evaluation of agricultural wastes (from primary production and secondary production), sewage sludge and food-processing wastes. Finally, the biomass availability was calculated at regional level, indicating the regions with low, medium and high potential. The conceptual approach of combining the benefits of relational database and GIS modeling was tested in two eastern European countries – in Latvia and Romania. This methodology was applied for biomass potential studies in the frame of European Commission IEE project “BiG>East”, assessing the theoretical biomass potential in six southern and eastern European countries. Existing methodology could be further developed in order to evaluate the technical feasibility of selected biomass; however, this is a task of future research.