Solid-state anaerobic digestion of spent wheat straw from horse stall

► Compared wheat straw (WS) and spent wheat straw (SWS) for biogas production. ► The methane yield of SWS was 50% higher than that of WS. ► Daily methane yield of SWS peaked several days earlier than that of WS. ► The cellulose degradation of SWS was 24.1% higher than that of WS. ► The hemicellulose degradation of SWS was 49.4% higher than that of WS.