Wheat straw (WS) was pretreated with four concentrations of H2O2 (1%, 2%, 3%, and 4%) and was anaerobically codigested with dairy cattle manure (CM) at various ratios from 100:0 to 0:100. Wet-state H2O2 pretreatment effectively enhanced the biodegradability and methane yield of the WS. The optimal concentration of H2O2 for treating WS was 3%. The methane yield was higher with the codigestion of CM and H2O2-treated WS than with untreated WS and higher than with H2O2-treated WS alone or CM alone. A 40: 60 ratio of H2O2-treated WS mixed with CM produced the highest yield of methane (320.8 mL g volatile solid (VS)(-1)). Results of high-throughput sequencing indicated that the methanogenic community shifted during the codigestion from the acetoclastic methanogens, Methanosarcina, to the hydrogenotrophic methanogens, Methanosphaera and Methanoculleus. (C) 2015 Elsevier Ltd. All rights reserved.