Viabilidade econômica de exploração de um biodigestor na produção de energia na cidade de Varginha/MG – estudo de caso

Abstract

The general objective of this work is to analyze the economic feasibility of the energetic exploitation of biogas produced at the Sewage Treatment Station Santana de Varginha/MG on the generation of electric energy. The production of biogas in a UASB/RAFA (Ascendant Flow Anaerobic Reactor) type sewage treatment systems consists of primary and secondary treatment, using an extended aeration sewage treatment system (degradation of organic matter by means of the addition of oxygen), which generates biogas due to the bacteria responsible for the production of methane (CH4). The greater the amount of methane produced is, the greater the efficiency of the burn and, therefore, energetic exploitation, will be, be it for electric energy or for the use of the generated vapors for the Sewage Treatment Station. For each resident, it is expected that 0.054 kg of DBO (Oxygen Biochemical Demand) be generated in the municipality in question. The amount of organic load is equivalent to a population of 140,000 residents, given that, in addition to domestic sewage, the sewage treatment station receives industrial sewage, recently treated at the industries. It is estimated that the sewage treatment station produce 1,850 m3 of biogas per day using the RAFA/USB system. Of this amount, 1,295 m3 is methane. Conceptualizing researches conducted regarding sewage biogas, and relating them with this study, as well as using mathematical formulas, will give a clearer and more objective view to outline a more coherent perspective of biogas generation, according to the structural and dynamic traits of the sewage treatment station. To increase the energetic potential and satisfy the energetic dependency of the sewage treatment station, given that, at a sewage treatment station, the expenses concerning electric energy are high, and the alternative (use of biogas) collaborates with the reduction of the consumption of electricity derived from the network. Thus, in terms of energetic efficiency, there will be a significant increase, allowing the sewage treatment station self-sufficient in energy, given that the amount of energy demanded from the sewage treatment process is high.