Improvement of Sugarcane Stillage (Vinasse) Anaerobic Digestion with Cheese Whey as its Co-substrate: Achieving High Methane Productivity and Yield

This study investigated methane production in an anaerobic sequencing batch biofilm reactor (AnSBBR) by co-digesting sugarcane vinasse and cheese whey. The assessment was based on the influence of feed strategy, interaction between cycle time and influent concentration, applied volumetric organic load (OLR A ), and temperature over system stability and performance. The system showed flexibility with regard to the feed strategy, but the reduction of cycle time and influent concentration, at the same OLR A , resulted in lower methane productivity. Increasing organic load, up to the value of 15.27 gCOD L −1 day −1 , favored the process, increasing methane yield and productivity. Temperature reduction from 30 to 25 °C resulted in worse performance, although increasing it to 35 °C provided similar results to 30 °C. The best results were achieved at an OLR A of 15.27 gCOD L −1 day −1 , cycle time of 8 h, fed-batch operation, and temperature of 30 °C. The system achieved soluble COD removal efficiency of 89%, methane productivity of 208.5 molCH 4 m −3 day −1 and yield of 15.76 mmolCH 4 gCOD −1 . The kinetic model fit indicated methanogenesis preference for the hydrogenotrophic route. At the industrial scale estimative, considering a scenario with a sugarcane ethanol plant with ethanol production of 150,896 m 3 year −1 , it was estimated energy production of 25,544 MWh month −1 .