Two-stage anaerobic digestion of food waste was performed using four different inoculum pre-treatment methods to enrich hydrogen (H-2) producing bacteria from sludge. The pre-treatments used in this study included heat shock, alkaline treatment, aeration, and a novel pretreatment using waste frying oil (WFO). Alkaline pretreatment and aeration did not completely inhibit methanogens in the first stage while no methane (CH4) was detected in the reactors cultivated either with heat shock or WFO-pretreated inocula. The highest H-2 and CH4 yields (76.1 and 598.2 mL/gVS, respectively) were obtained using the inoculum pretreated with WFO. The highest total energy yield (21.96 kJ/gVS) and total organic carbon (TOC) removal efficiencies (95.77%) were obtained using inoculum pretreatment with WFO. The total energy yield trend obtained using the different pretreatments was as follows: WFO > alkaline > heat > aeration > control. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.