Leaching of limonene fromorange wastes can be a lowenergy demanding method for removing the inhibition effects of the
wastes in the digestion process. The highest methane yield was obtained by pretreatment of the substrate at 20∘C for
10minwith orange peel waste and hexane ratio of 1 : 12 which results in three times higher methane yield compared to the
untreated wastes.