Co-digestion of biofuel by-products: Enhanced biofilm formation maintains high organic matter removal when methanogenesis fails.

Ethanol and biodiesel industries generate large volumes of by-products, such as vinasse and glycerol, which are suitable for biogas exploitation. This paper assessed the applicability and process performance of the anaerobic structured-bed reactor (AnSTBR) for the mesophilic (30 °C) continuous (105 days) anaerobic co-digestion of sugarcane vinasse and distilled glycerol under increasing organic loading rates (OLR) (0.5–5.0 kgCOD m−3d−1). The highest methane yield (211 NmL g−1COD rem.) and volumetric production (668 NmL L−1d−1) occurred at an OLR of 3.5 kgCOD m−3d−1. The performance of the AnSTBR showed high removal efficiencies of total COD (77.1%), carbohydrates (81.9%), and glycerol content (99.7%). Biofilm growth enhancement within the reactor offset the impairment of methanogenesis activity at high organic loads. The prompt biodegradability of glycerol reinforced the importance of gradually increase the organic load to prevent the buildup of volatile acids and maintain a stable long-term co-digestion system. [Display omitted] • Anaerobic co-digestion of sugarcane vinasse and distilled glycerol was assessed. • Biomass retention patterns in the co-digestion system were investigated. • The high biodegradability of glycerol required a gradual increase in organic load. • High organic matter removal (∼80%) was reached regardless of methanogenesis. • Enhanced biofilm growth offset impaired methanogenesis at high organic loads. [ABSTRACT FROM AUTHOR]