Biomass gasification systems may be relevant for decentralized power generation from recoverable agricultural and wood residues available in rural areas. Although they have many positive effects, these systems can also affect environment and human health. Indeed, during the process of biomass gasification, tars are produced and generally discharged in the local environment. This work deals with the analysis of the environmental impacts of a biomass gasifier power plant project. It compares the impacts of tar releases from the conversion of two biomasses: cotton stalks and rice husks, and that of two disposal modes (into water or on soil). The gate-to-gate environmental impacts are assessed through Life Cycle Assessment (LCA) approach. The results of this study indicate that the environmental impacts of electricity production from cotton stalks are higher than that of from rice husks. Results also show that the impact levels are high when tars are dumped into water comparatively to their discharge on soil. For environmental research, these results represent a significant step of a global environmental assessment of the studied systems.