Abstract The study investigated the effect of co-ensiling of cover crops (CC) and barley straw (BS) on biogas production. Blends containing chopped CC and BS (mix ratios of 1:0, 2:1, 3:1, 6:1; 10:1 and 19:1 (w:w)) were prepared and stored for 4 months prior to the biogas batch assay. Results show that CC is feasible for producing biogas with reasonable CH4 yield (330 mL CH4 gVS−1) and has good storability. Using of co-ensiling blends showed advantages over CC as it elevated the hydrolysis rate (k) from 0.024 to 0.061 d−1 and decreased the lag phase (from 5 to 0.8 days) during the thermophilic (51 °C) batch test. Synergistic effects were observed from both CH4 yield and hemi-cellulose removal. The finding provided an alternative strategy for integrated straw management and CC utilization for improved biogas production.