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

Energy security fosters the development of biogas, particularly in the context of the rapid energy transition. Substrates suitable for anaerobic digestion serve as feedstocks to produce biogas. Determining the optimal feedstock ratio is a key factor for achieving viable anaerobic digestion (AD) processes with high methane yields. This study evaluated different two-stage AD assays using biomass from a leguminous crop (Lupinus Albus, lupin) and olive mill wastewater (OMW). The highest methane yields were obtained in assays with higher proportions of lupin in the feed mixture (532 L kg VS−1 and 522 L kg VS−1) and at a higher Organic Load Rate (OLR) evaluated (510 L kg VS−1). Moreover, the presence of OMW in the feedstock significantly increased the Volatile Fatty Acid (VFA) concentration, as observed in the assay.