Circular economy in biorefineries: Scale-up of anaerobic/aerobic membrane bioreactors for vinasse recycling

The increased ethanol production driven by the growing demand for biofuels have the generation of vinasse as a negative aspect. Aiming for vinasse recycling, this study compared the performance of aerobic (AeMBR) and anaerobic (AnMBR) membrane bioreactors as alternatives for water, energy, and fertilizer recovery. In terms of organic matter, the AnMBR demonstrated a better removal efficiency (RAnMBR: 97%, RAeMBR: 92%) with significant differences. Higher values of chemical oxygen demand (COD) in the AeMBR permeate were correlated with the higher production of soluble microbial products and external polymeric substances. The opposite was observed in terms of total nitrogen removal since AeMBR showed better efficiency (RAeMBR: 80%, RAnMBR: 56%). Due to the higher fouling rate, the AeMBR required a higher increase in transmembrane pressure to guarantee a constant permeate flux and more frequent interruptions for membrane cleaning and maintenance. It would be able to recover 527 m³/h of permeate to be used in cane washing procedures or as feedstock for fertilizer obtainment, the latter with the expectations of better reuse of vinasse nutrients and lower environmental impacts compared with fertigation practices. Their demand (water and fertilizer), aligned with economic aspects, should be considered when deciding on the best reuse alternative. The AnMBR presented a higher operational cost (0.515 US$/m³) compared with the AeMBR (0.441 US$/m³). Nevertheless, the system allowed to recover 6.1 Nm³-CH4/m³-vinasse, which represents an energy production potential of 26.1 kW/m³-vinasse. Overall, the systems would allow for the higher valorization of vinasse, with better use of wastes and contributing to less dependence on raw materials. [Display omitted] •Water reuse has the potential to reduce the uptake from primary sources by 30%.•Biorefineries can increase their electricity independence through energy recovery.•MBR permeate: sugarcane washing. MBR concentrate: fertilizers feedstock.•Organo-mineral fertilizer is a better alternative when fertilization is considered.•AnMBR has greater performance and allows for higher vinasse valorization.