The development of bioenergy with carbon capture and storage (BECCS) technologies require the simultaneous assessment of their environmental performance and economic viability. Within the BioNETzero project, an integrated methodology is being developed to enable the comparison of different technological pathways based on a common process inventory. The environmental and economic assessments are based on process simulation results and detailed mass and energy balances developed for the Polish demonstration case. A shared inventory framework provides the basis for calculating key performance indicators (KPIs) in both Life Cycle Assessment (LCA) and Techno-Economic Assessment (TEA), ensuring methodological consistency between the two approaches. This integrated framework enables the identification of the main factors influencing both the implementation costs and the environmental performance of BECCS technologies, while providing a better understanding of the interactions between economic and environmental aspects. The integrated assessment of environmental and economic KPIs provides a basis for comparing different BECCS scenarios and supports the evaluation of their implementation potential under Polish conditions.