The objective of the present study is to discuss beneficial use of life cycle based assessment (LCA) for the decision-making on implementing local biomass projects. Focusing on a local biomass project in Miura City, Kanagawa Prefecture, we conducted document and interview surveys to clarify the introduction process of the project and examined when and how LCA can be used during the introduction process. The present study suggests that there are three possibilities in the production process to evaluate environmental and socio-economic impacts using LCA, namely, prospective, design and retrospective evaluations. In the Miura biomass project, although the planners did not conduct any evaluation of the project, they think that the prospective evaluation would have been beneficial because it can help get a consensus among the Congress and local stakeholders. The prospective evaluation using LCA can contribute to the design of a more effective project and the achievement of accountability in the earlier phases of local biomass projects by providing quantitative and objective information. Thus, the development of a practical method for the prospective evaluation of local biomass projects is required in the future.