Co-Digestion of Sugarcane Biorefinery Byproducts in Upflow Anaerobic Sludge Blanket Reactors, in Series, with Application of High Organic Loading Rate

Abstract

Anaerobic digestion of products from the sugarcane industry is an interesting option for biogas production. In this work, the anaerobic digestion of vinasse and sugarcane molasses supplemented with filter cake was performed in a two-stage upflow anaerobic sludge blanket (UASB) reactors system (R1 and R2). A volumetric methane production (VMP) of up to 4.3 L CH4 (L d)−1 was obtained for R1 + R2, with the application of an organic loading rate (OLR) in R1 of up to 45.0 g total COD (L d)−1. However, for OLR values higher than those applied, a shock load was observed, and only after its reduction was it possible to obtain stability again in terms of the pH, alkalinity, and acidity values in the UASB reactors, R1 and R2, which highlights the robustness of these anaerobic systems. With the decrease in the OLR after the shock load, the genera Trichococcus and Methanosarcina prevailed over Bifidobacterium and Methanobacterium in the sludge of the UASB reactor (R1). The use of two-stage UASB reactors for the co-digestion of vinasse, molasses, and filter cake allowed the establishment of a maximum OLR for the operation of anaerobic reactors under stable conditions in terms of the production of biogas and quality effluent. This could help the sugar and energy industries to produce methane in a sustainable and optimized manner.