Avaliação do potencial metanogênico na codigestão do pó de tabaco com dejeto suíno

Abstract

Anaerobic digestion (AD) is a biochemical treatment that makes it possible to produce energy from biogas and decrease the final disposal volume of different organic wastes. In this work, swine manure (SM) and tobacco powder were used, both produced in large volume and harmful to the environment when improperly disposed of. The differences in physicochemical properties amongst these residues are significant. The tobacco powder has a high cellulose content which can retard its degradability rate if used as a monosubstrate. In addition its concentration of organic carbon in relation to the concentration of nitrogen is high and it has little humidity. In contrast, SM have high water content and low organic carbon concentration. These differences prompt the development of anaerobic codigestion studies as an alternative to balance the nutrient/carbon/water ratio, improving process efficiency and; the use of tobacco powder as a potentiator of the AD process. This research aimed to identify the best biochemical condition to produce biogas and methane amongst different mixtures of tobacco powder and SM. The study was carried out on a laboratory scale in four phases on a batch scale at 35 °C using 1000 mL glass reactors with a workload of 500 mL. Inoculum and substrates were added in compliance with the requirements of the German standard VDI 4630 (2006). In Phase I, anaerobic sludge activity was tested by using microcrystalline cellulose as a reference substrate. In Phase II, preliminary tests were performed with this sludge and residues (tobacco powder and SM) to prepare a new inoculum for Phases III and IV AD and to identify the formulation that has the best BPB and MBP in Phase III, a test for the anaerobic activity of the digestate was performed (inoculum for the next phase), where the Phase I method was replicated. In Phase IV, this new inoculum was tested to identify the formulation that presented the best BPB and MBP. Based on the volatile solids mass of the residues in Phases II and IV, different tobacco powder dust:SM mixing ratios (1:1, 2:1, 3:1, 4:1, 5:1, and 6:1) were used. Simultaneously, tobacco powder and SM were digested as monosubstrates and comparative controls. The results indicate that the best BPB and MBP among different tobacco powder and SM mixtures presented a 6:1 ratio (tobacco powder:SM) during Phase IV and generated 683.30 m³ Biogas/tVS and 339.61m³ Methane/tVS, respectively. In general, the addition of tobacco powder, in terms of VS, provided a higher synergistic effect between the substrates favoring the production of biogas and methane.