In the European Union, the share of renewable energy has increased significantly over the past few years. Among renewable energy options, bioenergy is considered to be the dominant energy source. Previous literature is inconclusive regarding the suitability of bioenergy to mitigate greenhouse gases. The goal of this paper is to address this research gap. Life Cycle Assessments (LCAs) of biomass systems for electricity generation were gathered via a systematic literature review and form the empirical basis of this study. A quantitative exploratory analysis and a Qualitative Comparative Analysis were carried out to identify the greenhouse gas mitigation potential of different biomass systems used for electricity generation. Significant variations in LCA results are due to the heterogeneity of these systems; therefore, the transferability of LCA results to similar systems must be investigated on a case-by-case basis. Results show that electricity from biomass can be an appropriate measure for greenhouse gas mitigation in the European Union. To mitigate greenhouse gases, it is recommended to promote the employment of (1) non-dedicated lignocellulosic biomass with thermochemical conversion, (2) dedicated lignocellulosic biomass with thermochemical conversion, and (3) dedicated lignocellulosic biomass with direct combustion. For a more holistic assessment, future research should focus not only on greenhouse gas emissions, but also on other environmental, economic, and social impact categories.