Salix that was steam exploded at different conditions of temperature and time was anaerobically digested in a series of batch tests. Steam explosion proved to be favorable to increase the methane yields up to 50%, with best results obtained for temperatures starting at 210 degrees C. Batch studies for mixtures of cow manure and steam exploded Salix were performed, with C/N ratios varying from 31 to 56, related to volatile solids (VS) contents from 20 up to 80% of each of the substrates. Methane yields reached 230 mL CH4/g VS for the mixtures containing 30% and 40% VS of Salix over the total mixture's VS content (35 and 39 C/N ratio, respectively). A fraction up to 40% in VS from pre-treated Salix provided good methane yields with a faster digestion process. (C) 2011 Elsevier Ltd. All rights reserved.