Avaliação da biodigestão anaeróbia de resíduos alimentares e aguapé para a produção de biogás

Abstract

Anaerobic biodigestion is a promising technology pertaining the conversion of biomass into energy, with the aim of producing biogas from the process. Therefore, its use as a technique for treating organic solid waste yields positive results, enabling the proper management and treatment of these materials. This study aimed to evaluate the performance of biodigestion using food waste as substrate and Eichhornia crassipes (water hyacinth) as cossubstrate, verifying the effects of codigestion in relation to the potential of biogas production and the level of methane generated. The research was divided into two phases. The first made use of three bench reactors to evaluate different proportions of cossubstrate's total volatile solids. One reactor was used as a control, containing only inoculum (sludge from a UASB reactor) and substrate (food waste), while the remaining two were fed with 15% and 20% of TVS of cossubstrate (water hyacinth) in relation to the substrate. In the second phase of the study, the proportion of the bench reactor with the best performance (20%) was replicated in the reactor on a pilot scale, in order to assess the biodigestion of food waste and water hyacinth on a scale closer to a real one. In both phases, the parameters pH, alkalinity, volatile fatty acids, solids, chemical demand for oxygen, carbon and nitrogen were analysed, in addition to verifying the composition of the biogas produced specifically the percentage of methane. For the bench reactors, the results showed the potential of anaerobic codigestion using water hyacinth, so that the biodigester with the highest amount of cossubstrate inserted, 20% of TVS, presents itself as the most efficient in terms of organic matter's removal, efficiency of the process and yield of methane content. In this context, the pilot scale reactor showed a relative decrease in performance in relation to these criteria, with results below those expected. Among the possible justifications, there are the accumulation of VFA, the presence of materials that are difficult to degrade and the pilot reactor follow-up period shorter than planned. Even so, this biodigester was successful regarding the conversion of organic matter into biogas, since the production of gas and methane had satisfactory numbers, promoting the proper use and treatment of food and lignocellulosic waste, in order to enable the application of the technique for energy use of the methane produced.