Introduction // Photosynthesis, the Ultimate Beginning for Biorefineries // Features of First Generation Biorefineries // Cellulose, the Predominant Constituent of Biomass // Enzymatic and non-Biological Degradation of Cellulose // Hemicelluloses and Lignin, Other Key Constituents of Biomass // Pretreatments of Lignocellulosic Biomass // Biochemical Conversion of Biomass // Thermochemical Conversion of Lignocellulosic Biomass // Perspectives