Biogas: olive mill wastewater as complementary substrate of piggery effluent

ABSTRACT: he anaerobic digestion of a peculiar piggery effluent (PE), with a high organic content (93 g/L), was carry out using olive mill wastewater (OMW) as complementary substrate. From the different tested conditions–[100% PE],[70% PE+ 30% OMW],[50% PE+ 50% OMW],[20% PE+ 80% OMW]–units containing only PE and the lowest proportion of OMW in the mixture (30% OMW), provided the highest biogas volume of about 780 mL (70% CH4). Comparatively, identical quantities of each substrate ([50% PE+ 50% OMW]) generates some gas (320 mL, 60% CH4), understood as the result of an adaptation process by the microbial consortium, while the [20% PE+ 80% OMW] condition provided even less gas volume (120 mL, 6% CH4), probably due to the antimicrobial capacity of the phenolic compounds in OMW, confirming the negative influence of using so high OMW proportion.