Abstract The study was aimed to compare the methane potential from the silage of Sida hermaphrodita mixed with cattle manure pretreated by microwave (MW) thermohydrolysis with liquid hot water (LHW) pretreatment. It was illustrated that both pretreatment methods significantly improved degradation of the lignocellulosic structure and improved the methane production. The maximum methane production of MW pretreated biomass was 590 NL/kg VS at 150 °C and 15 min with an improvement of 39.1% to an untreated sample. In turn, LHW treatment provided the maximum methane production of 575 NL/kg VS with the same pretreatment conditions. The net energy output significantly higher than calculated for the control sample was achieved only for MW pretreatment at 150 °C and 15–30 min. In other variants, pretreatment step needed higher energy input than the net energy gain from methane production.