This paper presents the results of an experimental methane fermentation study on untreated, NaOH and hydrothermal pretreated substrates of wheat straw. Experiments were conducted at 37 degrees C (mesophilic temperature). Substrates concentration were maintained at 4.45% VS (44.5 g VS/L). Untreated wheat straw substrate had resulted into specific methane and biogas production yields of 78.4 L/kg VSa and 188.4 L/kg VSa, respectively. The specific methane and biogas production yield of NaOH pretreated wheat straw substrate had resulted into 165.9 L/kg VSa and 353.2 L/kg VSa, respectively. Hydrothermal pretreated wheat straw substrate had resulted to yield specific methane and biogas production of 94.1 L/kg VSa and 205.7 L/kg VSa, respectively. NaOH pretreated substrate produced 87.5% higher biogas production and 111.6% higher methane production compared to the untreated wheat straw substrate. Hydrothermal pretreated substrate had resulted into an increase of 9.2% in biogas production and 20.0% in methane production compared to that of untreated wheat straw substrate. (C) 2012 Elsevier Ltd. All rights reserved,