Estudo dos processos envolvidos na compostagem de tabaco de cigarro contrabandeado em reator facultativo por meio de técnicas convencionais, cromatográficas, espectroscópicas e de microscopia

Abstract

Composting in facultative reactors has emerged as an efficient and low-cost technology for treating organic solid waste, such as food scraps and contraband cigarette tobacco. Given this context, the present study aimed to investigate the mechanisms involved in facultative reactor composting of contraband cigarette tobacco mixed with food waste, using conventional, spectroscopic, chromatographic, and microscopic techniques. Process monitoring was conducted through temperature, pH, moisture, and C/N ratio tracking, as well as respirometric analyses, seed germination index (SGI), chromatography, and Scanning Electron Microscopy (SEM). Compost maturity and stability were assessed by spectroscopic techniques (UV/Vis and FTIR). Compost quality was determined through analyses of heavy metals, total phenols, and NPK nutrients, in addition to its potential use for seedling production. The results showed that facultative reactor composting effectively controlled moisture, promoting exposure of the compost to thermophilic temperatures. The low initial C/N ratio of 18 allowed for the treatment of large amounts of waste. Respirometric analyses indicated a reduction in the metabolic activity of decomposer microorganisms over time, while the SGI revealed a non-toxic compost after 130 days. SEM and chromatography demonstrated that the primary process occurring at the top of the reactor is aerobic, anaerobic at the bottom, and facultative in the middle. A decrease in the E4/E6 ratio and an increase in peaks and bands in FTIR spectra, characteristic of aromatic groups, indicated compost stability and maturity after 130 days. The final compost presented NPK concentrations of 18.49 for reactor 2 and 25.26 for reactor 3, values beneficial for plant development. Concentrations of potentially toxic metals, such as Co, Ni, Cu, Mn, Fe, Cd, Pb, and Cr, were below the permissible limit for organic compounds, and a 93.67% reduction in total phenols demonstrated the efficiency of the process. During composting, pathogens Escherichia coli and Salmonella spp. were not eliminated, indicating the need for a liming step. At proportions of 70%, 25%, and 80%, the compost promoted the growth of tomato, cucumber, and bracatinga seedlings, respectively. In conclusion, the facultative reactor operates with three distinct degradation zones (aerobic at the top, anaerobic at the bottom, and facultative in the middle), and composting of contraband tobacco produced stable, non-toxic, nutrient-rich compounds suitable for agricultural use.