Legume as Vegetal Nitrogen Source with Olive Mill Wastewater for Methane Production Through Two-Stage Anaerobic Co-Digestion Process

Energy security benefits the development of biogas and is particularly evident in a context where the energy transition is advancing rapidly. Anaerobically susceptible substrates constitute the raw material to generate energy in a biogas way. To establish the raw mate-rial ratio in the feed is a key factor to make a viable process of Anaerobic Digestion (AD) achieving high biogas yields. This research performed different assays of AD separated in two stages increasing a profitable leguminous (Lupinus Albus) crop (L) and the Olive Mill Wastewater (OMW). The most elevated values of methane yield belonged to assays where the amount of L is higher in the fed mixture (532 L kg VS-1 and 522 L kg VS-1) and the Or-ganic Load Rate (OLR) evaluated is higher (510 L kg VS-1). Also, the presence of OMW in the fed mixture indicates the increase of Volatile Fatty Acids (VFA) concentration because significant differences were found in assays studied. Two kinetic models were fitted to Chemical Oxygen Demand (COD) removal data (Grau Second Order and Modified Stov-er-Kicannon).