Digestão anaeróbia em duas fases de resíduos de mortalidade suína e redução de amônia livre utilizando processo com membrana

Abstract

Swine mortality residues (SMR) represent a growing environmental and sanitary challenge in commercial farms, driven by the intensification and concentration of production. Anaerobic digestion (AD) is an established technology for the treatment and valorization of agricultural waste, allowing for energy recovery in the form of biogas. However, substrates such as swine carcasses have a high protein and lipid content, the degradation of which generates ammonia and fatty acids that, in high concentrations, can inhibit microbial activity. In this context, the use of gas-permeable membranes (GPM) emerges as a promising alternative to mitigate the effects of ammonia inhibition, promoting greater process stability. Therefore, this thesis evaluated the use of two-stage anaerobic digestion (TSAD) and GPM as complementary strategies for the treatment and utilization of SMR. In this sense, two sets of experiments were conducted. The first one evaluated the potential of TSAD in the production of H2 and CH4, comparing it to single-stage digestion (CH4), through batch tests. Separating the stages increased methane production by 55%, favoring energy recovery and improving the degradation kinetics of the carcasses, as confirmed by the modified Gompertz model. The second experiment evaluated the use of GPM in ammonia recovery and mitigation of nitrogen inhibition. Two semi-continuous reactors were operated with swine manure supplemented with urea, simulating nitrogen load increases. One of the reactors was equipped with GPM for in-situ removal of free ammonia (FA). The activation of GPM allowed for continuous ammonia recovery and restored methane production when FA levels exceeded 500 mgN L-1 . Microbiological analysis indicated changes in the methanogenic community, with a predominance of more tolerant groups, such as Methanosarcina. Overall, the results indicate that TSAD and the use of GPM are effective and complementary strategies for the treatment of nitrogenous substrates, increasing the operational robustness, energy efficiency, and environmental viability of AD applied to SMR.