Liquid hot water (LHW) and alkaline pretreatments of giant reed biomass were compared in terms of digestibility, methane production, and cost-benefit efficiency for electricity generation via anaerobic digestion with a combined heat and power system. Compared to LHW pretreatment, alkaline pretreatment retained more of the dry matter in giant reed biomass solids due to less severe conditions. Under their optimal conditions, LHW pretreatment (190 degrees C, 15 min) and alkaline pretreatment (20 g/L of NaOH, 24 h) improved glucose yield from giant reed by more than 2-fold, while only the alkaline pretreatment significantly (p < 0.05) increased cumulative methane yield (by 63%) over that of untreated biomass (217 L/kg VS). LHW pretreatment obtained negative net electrical energy production due to high energy input. Alkaline pretreatment achieved 27% higher net electrical energy production than that of non-pretreatment (3859 kJ/kg initial total solids), but alkaline liquor reuse is needed for improved net benefit. (C) 2016 Elsevier Ltd. All rights reserved.