The energy crisis resulted in increasing awareness that alternative sources of energy should be considered. During this time, Brazil implemented ethanol production from sugarcane as biofuel. However, during this process, large amounts of residues are generated, such as vinasse. This residue can be treated anaerobically to generate methane as a source of bioenergy with the use of sequencing batch reactors operated with immobilized biomass (AnSBBR). In this work, tests were conducted in an AnSBBR laboratory-scale reactor, and the main results regarding the kinetic model fitting and performance of substrate consumption (83 %), methane content in the biogas (77 %), applied organic load (5.54 g COD L(-1) day(-1)), methane productivity (973 N-mL CH4 L(-1) day(-1)), and yield (9.47 mol CH4 kg COD(-1)) show that AnSBBR is a promising technological alternative. After tests conducted in a laboratory-scale reactor, an industrial reactor was scaled and was also operated in a sequencing batch with immobilized biomass (AnSBBR) for the anaerobic treatment of vinasse with the goal of generating methane and environmental suitability to further disposal in soil. The calculations were performed based on data from a sugar and alcohol plant located in São Paulo, Brazil. This study proposes to the operation of the industrial scale reactor was the association of four AnSBBR (each one with a volume of 15849 m(3)) operating in parallel (with a feeding and discharge time of 4 h and a reaction time of 8 h), with the goal of adapting the treatment system from a discontinuous operation to a continuous operation. In this industrial scenario, the methane production was estimated at 1.65 × 10(6) mol CH4 day(-1), and the energy was approximately 17 MW, increasing the possible energy recovery contained in sugarcane from 93 to 96 %.

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The most common approach to deal with vinasse (sugarcane stillage) is fertigation, but this technique compromises soil structure and surrounding water bodies. A possible solution is to transport vinasse to local cheese whey producers and perform the co-digestion of these wastewaters together, reducing their organic load and generating bioenergy. Therefore, this study investigated the application of an AnSBBR (anaerobic sequencing batch biofilm reactor) operated in batch and fed-batch mode, co-digesting vinasse and whey at 30 °C. The effect of influent composition and feeding strategy was assessed. In all conditions, the system achieved high organic matter removal (approximately 83%). Increasing the percentage of vinasse from 0 to 100% in the influent resulted in a decrease in methane productivity (76.3 to 51.1 molCH m day) and yield (12.7 to 9.1 molCH kgCOD), but fed-batch mode operation improved reactor performance (73.0 molCH m day and 11.5 molCH kgCOD). From the kinetic metabolic model, it was possible to infer that, at the best condition, methane is produced in a similar way from the acetoclastic and hydrogenotrophic routes. A scheme of four parallel reactors with a volume of 16,950 m each was proposed in the scale-up estimation, with an energy recovery estimated in 28,745 MWh per month.

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This work studied the feasibility of biohydrogen production by co-digestion of vinasse/molasses in an AnSBBR operated with mechanical stirring (30°C and 200 rpm). Hydrogen production by co-digestion of vinasse/ sucrose was also studied to verify the performance of the process with a known co-substrate with easy degradation. The effects of influent composition (vinasse/sucrose and vinasse/molasses), influent concentration (3000 and 4000 mgCOD.L -1 ) and cycle time (3 and 4 h) on performance indicators were evaluated using stability, organic matter removal efficiency, molar hydrogen yield, productivity and biogas composition. The condition with vinasse/molasses in the influent that showed the best results was obtained with a 3-hour cycle time, influent concentration of 3000 mgCOD.L -1 and composition of 33% vinasse and 67% molasses. The molar productivity in this condition was 3.8 molH 2 .m -3 .d -1 with a hydrogen molar fraction of 16% (and a methane molar fraction of 14%). A first order kinetic model was fitted efficiently to the best conditions.