Adaptação de lodo mesofílico à condição termofílica para fermentação escura de resíduos de frutas e verduras gerados na central de abastecimento do Ceará.

Abstract

The population growth observed in recent years involves several consequences, one of which stands out for this work: the increase in demand for energy and food products. The problem involving the increase in demand for energy is related to Brazil's dependence on non renewable and polluting energy sources, which drives the study and use of renewable energy sources, such as obtaining combustible gases (such as hydrogen gas) by the middle of dark fermentation. Furthermore, the increase in demand for food products is also characterized as a socio-environmental problem, since, when not consumed by the population, this waste is discarded, mainly, in Supply Centers, which makes it a cause of negative environmental impact. Therefore, the purpose of this research project is to evaluate the production of hydrogen gas (H2) from dark fermentation, in mesophilic and thermophilic conditions, of mixed culture with organic waste of fruits and vegetables. In the first stage of this research, the efficiency of three anaerobic inoculum pre-treatment methods (chloroform addition method, acid shock method, and heat shock method) was evaluated for inhibiting the methanogenic metabolic step of anaerobic digestion, with better performance attributed to thermal pretreatment, with accumulated production of 90 mL H2 and yield of 2,7 mol H2/mol Sucrose. In the second stage of this research, the effect of a stepwise increase in operating temperature (from 35ºC to 45ºC) on the production of hydrogen gas (H2) was evaluated, with better performance attributed to a temperature of 43ºC, with an accumulated production of 552 mL H2 and a yield of 4,9 mol H2/mol Sucrose. In the third stage of this research, the accumulated production and yield of hydrogen gas (H2) were evaluated in the dark selection of fruit and vegetable shortages at 30ºC and 43ºC, which was proven by highlighting the temperature of 43ºC as the most efficient for the production of hydrogen gas (H2), with an accumulated production of 265 mL H2 and a yield of 7.3 mol H2/mol Sucrose, while the temperature of 30ºC resulted in an accumulated production of 104 mL H2 and a yield of 3.1 mol H2/mol Sucrose. Finally, for future studies, it is suggested to use an operating temperature of 43ºC in high-rate reactors to produce hydrogen gas (H2) from fruit and vegetable waste.