Inclusão de enzimas digestivas no processo de digestão anaeróbia de dejeto bovino e grãos de milho em reatores semi- contínuos

Abstract

Brazil stands out as one of the largest producers of grains and cattle in the world, activities that generate large amounts of waste, which in turn, have high potential for the production of biogas. Thus, this study aimed to evaluate the production and quality of biogas produced in continuous biodigesters, during the processes of monodigestion and anaerobic co-digestion of bovine manure (BD) and industrial residues of corn grains (GM) with the presence or absence of digestive enzymes. The experiment was carried out in a completely randomized design, in a 2x2 factorial scheme (substrate x enzymes), with 4 replications, totaling 16 experimental units. The treatments were the inclusion of agro-industrial residues of corn grains (GM) in the bovine manure (DB), with the presence or absence of digestive enzymes, being: DB+E: 100% DB, with enzyme; DB: 100% DB, no enzyme; DB/GM+E: 70% DB and 30% GM, with enzyme; DB/GM: 70% DB and 30% GM, without enzyme. The efficiency of the treatments was evaluated by the reduction of total solids, volatile solids, pH, alkalinity, C/N ratio (carbon/nitrogen) and specific production of biogas and methane, in addition to the chemical composition (proteins, non-structural carbohydrates, ether extract, crude fiber, neutral detergent fiber and acid detergent fiber) from cattle manure and corn grains. In biogas, CH4, CO2, N2 and O2 contents were analyzed. The contents of nitrogen, phosphorus and potassium in the biofertilizers were analyzed. The application of enzymes, in DB monodigestion or DB/GM co- digestion, did not result in higher biogas and methane production. DB/GM co-digestion, independent of the addition of enzymes, promotes greater production of biogas and methane. Anaerobic digestion of substrates, without the inclusion of enzymes, was more efficient in reducing SV levels. The specific productions of biogas and methane were higher for the co- digestion processes, when there was no addition of enzymes. DB/GM co-digestion processes showed greater potential for biogas production, per kilogram of total and volatile solids added.