Biocarvão e bacillus sp.: caracterização, mineralização de carbono orgânico e influência no solo.

Abstract

This study aimed to characterize and produce biochars using a "double drum" type furnace and a muffle furnace from different biomasses, and to evaluate the interaction of sewage sludge biochar with microorganisms belonging to the genus Bacillus sp. during the mineralization process and its effect on soil fertility. This work was divided into chapters as follows: the first chapter contains the introduction, objectives, and literature review; in the second chapter, the production of biochars from sewage sludge, poultry litter, rice straw, coconut fiber, and pineapple residue biomass was carried out using a muffle furnace and a double drum furnace, and their characterization, as well as that of their respective raw biomasses, was based on their physical and chemical characteristics through proximate analysis, following the ASTM: D1762-84 (2007) methodology; Fourier Transform Infrared Spectroscopy (FTIR); and X-ray diffraction. Statistical analyses were conducted using the SISVAR statistical software. Experiments were also conducted solely with sewage sludge biochar due to its high phosphorus and other nutrient content, aiming to evaluate carbon (C) mineralization when incorporated into the soil (Chapter III) and the soil's chemical characteristics after the incubation period, according to Teixeira et al. (2017) (Chapter IV). The experiments were conducted in the Irrigation and Salinity Laboratory (LIS) of the Federal University of Campina Grande (UFCG). The soil used was collected in the municipality of Lagoa Seca 3 PB, and the sludge was obtained from the Basic Sanitation Program Laboratory (PROSAB). The quantification of released CO2 was performed through the titration of 0.5 ml L-1 NaOH with a standardized 0.4 mol L-1 HCl solution over 104 days, in addition to evaluating the kinetics of carbon mineralization following two first-order equation models and two simultaneous reactions (MURWIRA et al., 1990; MOLINA et al., 1980, respectively), and finally the half-life analysis of mineralization (SPOSITO, 2008) (Chapter III). Generally, the highest carbon contents were observed in the raw plant-based biomasses (pineapple residue, coconut fiber, and rice straw) and in the biochars produced in both the muffle and double drum furnaces. The highest phosphorus (P) concentrations were observed in the sewage sludge and poultry litter biomasses, with the highest amount found in the sewage sludge biomass produced using the double drum furnace. The rice straw biochar had the highest moisture content, while the poultry litter had the lowest; the highest volatile content was found in the poultry litter biochar compared to the other biochars. The highest ash content was observed in the rice straw and coconut fiber biochars, with no statistical differences between them. The highest fixed carbon content xix was found in the rice straw biochar, in both production methods. Regardless of the biomass used in this study, a band at ≈3300 cm-1 was observed, attributed to (O-H) vibrations in the hydroxyl group present in cellulose (Chapter II). Overall, regardless of the doses of sewage sludge biochar and Bacillus sp. applied to the soil, the carbon mineralization rate was higher at the beginning of the incubation period, gradually decreasing (Chapter III). The maximum P value estimated by the regression equation model that fit the data was obtained with the application of a dose of 15 t ha-1 of biochar combined with 8.2 x 10^7 CFU ml-1 of Bacillus sp., with a variation of 418% observed for this variable compared to the control. The organic carbon (OC) values increased quadratically after the addition of sewage sludge biochar, with the highest estimated carbon value being 8.6 g kg-1 at a dose of 8.9 t ha-1 (Chapter IV).