In this study, a comprehensive model for assessing environmental, economic, and social impacts of biofuels, which include both liquid biofuels and biopower (electricity generated from biomass), in California will be developed based on Life Cycle Assessment (LCA). The term 'Biofuel' in this study will represent both liquid biofuels and biopower as transportation fuels. Afterwards, the optimal and preferable pathways from various biomass feedstocks to liquid biofuels and biopower will be shown based on the model focusing on agricultural residues to analyze the availability, key issues, and uncertainties in them. The study also aims to investigate possible consequences of changes in biofuel pathways under different conditions such as locations or regulatory policies. This study will contribute to current knowledge in the following ways: 1) it develops an integrated model for assessing environmental, economic, and social impacts of biofuel pathways including geographic variability; 2) it identifies preferable biofuel pathways from the standpoint of feedstock, conversion technology and energy product; 3) it provides relevant information for decision-making on the part of industry, policy makers, and communities involved in biofuel siting and investments; and 4) it suggest useful frameworks for social LCA on biofuel and for consequential effects of changes in biofuel pathways.