Exergy Analysis of Biogas Production from Sugarcane Vinasse

The use of agro-industrial and urban organic waste to produce energy seems to be one of the most attractive options for the future of energy supply. Anaerobic digestion is a promising process for treating organic waste and producing biogas. Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide, and hydrogen sulfide, that can be used for electrical and thermal energy generation or as fuel. However, it is still necessary to improve the technology associated with its production, adapting it to an efficient, safe, and competitive scale. Various methodologies are used to support the decision on process parameters and operating conditions to find the most effective and sustainable ones. In this study, an exergy analysis was performed to determine the exergetic efficiency and exergy destruction in the biogas process produced from the anaerobic digestion of vinasse. The analysis was performed through mass, energy, and exergy balances using literature data and computer simulation and considering the use of a continuous stirred tank reactor. The results show that the exergy destroyed in the CSTR biodigester was 1338.9 kW, accounting for 57.2% of the overall exergy destruction in the process. The heat exchanger showed the highest exergy efficiency (99.95%), with only 5.77 kW of exergy being destroyed. The authors suggest for future works that it would be interesting to perform a life cycle assessment (LCA) and exergoeconomic analysis to evaluate the environmental and economic impacts associated with biogas production from the anaerobic digestion of sugarcane vinasse.