The use of energy crops (maize straw, wheat straw, barley straw etc.) as substrate for renewable energy production (e.g. biogas) is more efficient when it is degraded by different hydrolysis methods. However, fibers contained inside energy crops (e.g. cellulose and hemicellulose) are only hardly and slowly degraded by anaerobic bacteria. The slow degradation of these substances can decrease the methane yields of agricultural biogas plants.In the present study, we investigated the efficiency of combined pretreatment (different concentrations H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis. Testing different concentration of H2SO4, good results were obtained for maize whole crop when we used combined pretreatment (3% H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis (3.9 fold higher) and for Gavott Maize Straw when we used combined pretreatment (2% H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis (3.6 fold higher) comparing with untreated samples.