Potencialização da produção de biogás e metano com adição de carvão ativado granular na digestão anaeróbia semisseca de dejeto suíno

Abstract

Pig farming is an important agricultural activity responsible for one of the largest supplies of animal protein in the world. However, there is a lack of infrastructure for the management of swine waste, deposited in anaerobic ponds or released directly into the environment, being responsible for a high emission of greenhouse gases (GHG). Thus, energy recovery from the anaerobic digestion (AD) of swine manure through bioprocesses that are capable of converting this organic waste into a biogas rich in methane (CH4), producing fertilizers and reducing environmental pollution stands out. However, the AD of this complex organic matter suffers interference, caused by its high solids content, making it difficult for microorganisms to convert the substrate during the hydrolysis and methanogenesis steps. Therefore, this biological process was improved from the thermo-alkaline pretreatment of swine manure, aiming to improve the bioavailability of the substrate, and the addition of the conductive material granular activated carbon (GAC), in order to assist in the syntrophic activity of microorganisms. The objective of this work was to kinetically evaluate the increase in biomethane production with the addition of different concentrations of GAC in the semi-dry anaerobic digestion of swine manure using a microbial consortium from brewery sludge as the source of inoculation. The experiment was carried out in batch, with 300 mL reactors and a useful volume of 70 mL, with a total solids content around 10%, inoculated with anaerobic sludge at a substrate/inoculum ratio equal to 1, at a mesophilic temperature of 37ºC under agitation orbital of 150 rpm for 90 days. The results showed that the biogas yield of the reactor that contained 10 g/L of CAG was 360.8 mL/gSV, approximately 31% higher than the reactors with the other concentrations of conductive material, and the biomethane yield was 190.2 mL/gSV, on average 22% higher than the reactors with 20 and 30 g/L of GAC added. Each reactor obtained an adequate kinetic model to describe the respective biogas production curve, making it possible to mathematically evaluate the bioprocess. Therefore, the addition of granular activated carbon in the anaerobic digestion of swine manure under semi-dry conditions is a sustainable biotechnological alternative for the destination of this potentially toxic residue for the environment.