Energy issues nowadays are one of the critical priorities for the United States. There is a strong desire and tremendous efforts employed towards replacing fossil fuels with sustainable alternative sources of energy. In this study, hydrothermal liquefaction with ethanol and water as co-solvents was applied on giant miscanthus (Miscanthus giganteus) perennial biomass feedstock. Four temperatures and six ethanol ratios were chosen for the study. The optimum combination of temperature and water/ethanol ratio was 280 degrees C and 50%, respectively. The effect of time, biomass to solvent ratio and catalyst type was studied as well. The best liquefaction results without applying catalysts (53% oil yield and 8% solid residue) were obtained after 15 min. When zinc chloride was used as catalyst, more than 52% of oil yield with 1% solid residue was obtained after 5 min. The crude bio-oil chemical composition was identified by using gas chromatography/mass spectrometry (GC/MS). (C) 2014 Elsevier Ltd. All rights reserved.