Banca de DEFESA: NADJANE LEITE DOS SANTOS TELLES

Hydrogen production from craft brewery wastewater by natural fermentation

Experimental design, inoculum, Energy.

Technological development and changes in people's habits have increased the global need for energy and have been a concern of modern society. The search for sustainable energy development is an important issue in order to avoid an energy crisis and minimize the environmental impacts that occur due to the use of fossil fuels for many years. Given this scenario, hydrogen appears as an alternative source of energy, since its combustion generates only oxygen and water, thus being considered a clean and renewable fuel. The biological production of hydrogen, through anaerobic digestion, appears as an alternative for the processing of craft brewery waste, making it possible to combine energy generation (biogas) with the environmental framework of this waste without interfering with its quality. In this sense, the objective of this study was to evaluate the production of hydrogen from beer residue as a carbon source, seeking to establish optimal experimental conditions, using an experimental design 2³, to evaluate the effect of the variables (Chemical Oxygen Demand - COD, type of inoculum and agitation) in two levels, resulting in 8 different experiments, carried out in duplicate, totaling 16 assays. The COD concentrations used were approximately 5 and 10 g. L^-1, inoculum from natural fermentation and an anaerobic sludge, some reactors were submitted to agitation at 120 rpm and others kept without agitation. The effects of the dependent variables on the production of H2 were examined by analysis of variance (ANOVA) and the accumulated production was adjusted by means of the modified Gompertz function using the average of the values obtained by the replicas of the reactors in each treatment of the experimental design. The coefficients of determination (R²) of all adjustments were from 0.9916 to 0.9975, indicating that the applied model satisfactorily describes the progress of the cumulative hydrogen production. The maximum potential for hydrogen production and the production rate were obtained in reactor 5 (COD of 5 g. L^-1, inoculum of natural fermentation and agitation of 120 rpm) in the values of 163.30 mL, and 0.52 mL /h, respectively.