Leaching or solid-liquid extraction is an alternative pretreatment performed in roomtemperature. In this technique,the limonene in the orange peel waste is leached into a solvent that has contact with the peel [18]. This technique is widely
used to extract organic compounds from natural materials, where these compounds are present at low concentration.
To the best of our knowledge, this technique has not been employed for pretreatment of orange peel wastes.Therefore,
the objective of this work was to examine leaching technique for orange peel waste pretreatment with focus on biogas
production.