The bio-oil synthesis from a mixture of wastes (7 wt.% straw, 38 wt.% wood, and 45 wt.% grass) was carried out by direct liquefaction reaction using Raney Nickel as catalyst and tetralin as solvent. The green wastes were biologically degraded during 3 months. Longer the destructuration time; higher the yield into oil is. Biological pretreatment of green wastes promotes the liquefaction process. Among the components of degraded biomass, Humin, the major fraction (60-80 wt.%) that was favored by the biological treatment, yields to a bio oil extremely energetic with a HHV close to biopetroleum (40 MJ kg(-1)), contrariwise, Fulvic acids (2-12 wt.%), the minor fraction is refractory to liquefaction reaction. (C) 2014 Elsevier Ltd. All rights reserved.