Intensification of methane production from waste frying oil in a biogas-lift bioreactor

Abstract Biogas upgrading from anaerobic digestion of waste frying oils (WFO) was accessed in this study. For that, two bioreactors (Rb-biogas-lift bioreactor with gas and liquid recirculation, Rc-control reactor recirculation) were fed three times per week, a mixture WFO, glycerol volatile fatty acids (VFA). Rb produced 1.4 more biogas higher methane content (79%) than Rc (67%). Higher relative abundance hydrogenotrophic methanogens (34%–39%) observed Rb, when compared to (16%–21%). The Sprochaetia class, which includes some homoacetogens/syntrophic acetate oxidizing genera, also Rb. This work shows that recirculation applied the biogas-lift facilitated WFO degradation, most probably due selective enrichment methanogens. Recirculation CO2 present reverse homoacetogenesis (i.e. syntrophic oxidation) seem be main factors involved stimulation methanogenesis.