Avaliação da viabilidade da bioconversão do bagaço de cana-de-açúcar em metano por meio da digestão anaeróbia.

Abstract

Sugarcane is a renewable energy source and abundant in Brazil. It is used to produce sugar and ethanol and in its process there is a big production of waste as vinasse, marc and others. These residues can be used for energy purposes by direct combustion. An alternative is anaerobic digestion, a process where bacterial mass performs the conversion of bagasse into biogas and then in bioenergy. To facilitate the digestion of sugarcane bagasse is necessary that its main constituents (cellulose, hemicellulose and lignin) be disaggregated. For that it is generally used a thermal process, the steam explosion. In this study it was used sugarcane bagasse pre-treated with steam explosion to evaluate their conversion into methane by anaerobic digestion in reactors with feeding regime in sequential batch. Furthermore, it was conducted in two phases, which were used reactors unit. In the first phase a reactor was operated r with industrial sludge, another with bovine rumen and the third with the addition of industrial sludge and industrial enzymes (cellulase and xylanase), all at constant humidity and mesophilic conditions. In this phase the biggest efficiency in terms of removal of volatile solids was obtained in the reactor with enzyme (R3), followed by the reactor with rumen (R2) and by the reactor only with sludge (R1). In the second phase a control reactor (R1)was operated , a second reactor with addition of enzymes only in feed (R2) a third (R3) fed with bagasse already hydrolyzed in a dedicated enzymatic hydrolysis reactor and a forth with addition of enzymes and sludge recirculation (R4), all at the same temperature and humidity. In this last stage the efficiency was low for R1, R2, R3 and R4, . Even at this stage characterization was performed of the bagasse and the digested slurry in the reactors. It was found that the composition of the slurry was not very different from that of the bagasse . As alternatives for disposal of the discarded material, the possibility of drying on the natural beds was analyzed both in the open air and on beds covered with plastic. The experimental research showed that drying would require a very large area to the beds, because the productivity was low. Based on the results presented here, it becomes clear that for the anaerobic digestion to become the best way of using the sugarcane bagasse, generated in the sugar industry, many mechanisms have yet to be properly studied.