Influência do inóculo na produção de hidrogênio a partir de resíduo de cervejaria artesanal

Abstract

Technological development and changes in people's habits have increased the global need for energy and have been a concern for modern society. The search for the development of sustainable energy is an important issue in order to avoid an energy crisis and minimize the environmental impacts that have occurred due to the use of fossil fuels for many years. Given this scenario, hydrogen emerges as an alternative source of energy, as its combustion only generates water vapor, without harming the environment or contributing to the greenhouse effect, thus being considered a 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 the generation of energy (hydrogen) 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 collected from the fermentation tank as a carbon source, seeking to evaluate the effects of Chemical Oxygen Demand – COD (5 and 10 g. L-1 ), type of inoculum (Natural fermentation and anaerobic sludge) and agitation (without agitation and 120 rpm). The effects of the dependent variables on H2 production were examined by analysis of variance (ANOVA) and the accumulated production was adjusted using the modified Gompertz function using the average of the values obtained by the reactor replicates in each treatment of the experimental design. he linear effect of COD and type of inoculum; the effect of the interaction of COD and inoculum type and the interaction of inoculum type and agitation were highly significant on maximum hydrogen production, indicating that these terms had a great impact on the response variable. The effect of agitation and the interaction between COD and agitation had little impact on hydrogen production. The coefficients of determination (R2) of all adjustments ranged from 0,9916 to 0,9975, indicating that the applied model satisfactorily describes the progress of cumulative hydrogen production. The maximum hydrogen production potential and production rate were obtained under the conditions (COD of 5 g. L-1 , natural fermentation inoculum and agitation of 120 rpm) at values of 163,30 mL and 0,52 mL. h-1 , respectively. The main metabolites produced were methanol, ethanol, acetic acid, propionic acid, butyric acid and valeric acid. Genetic sequencing analysis revealed that the species Enterobacter sp. was the one that showed the greatest similarity in the reactor inoculated with natural fermentation with the highest hydrogen production and the uncultured bacteria were the ones that showed the greatest similarity with the reactor inoculated with ETE sludge with the lowest H2 production.