Avaliação da produção de biometano em biodigestores com sobras e restos de alimentos por meio de recirculação e inoculação de consórcio microbiológico

Abstract

The increasing energy demand, the growing volume of waste, the challenges in its proper management, and consequently its inadequate final disposal have necessitated the search for sustainable solutions. Accordingly, this study aimed to evaluate the generation of biogas and biomethane produced through anaerobic digestion of food waste in reactors with different recirculation configurations, varying organic loads, and utilizing a hydrolytic microbial consortium. In an initial phase, two 1.3 m3 reactors were operated semi-continuously: reactor 01 with recirculation at four bottom points and reactor 02 with a single bottom point. Subsequent phases assessed the effect of varying organic load (1% and 5% volatile solids – VS) and bioaugmentation with a hydrolytic microbial consortium (Bacillus subtilis [KJ870046.1] and Alcaligenes faecalis [CP013119.1]). Subsequently, the potential use of the digestate as biofertilizer was evaluated. Various physicochemical parameters were monitored over 90 days. Reactor 01 demonstrated higher efficiency in organic matter degradation, with lower solid concentrations and 60% volatile solids (VS) removal, compared to 8% in reactor 02, in addition to producing more biogas (35.80 Nm3) and biomethane (67.17%) than reactor 02 (26.73 Nm3 biogas and 64.57% biomethane). In the subsequent phases, the microbiological reactor with 1% VS (RM1) and the control reactor with 5% VS (RC5) showed higher efficiency in organic matter degradation with 71% VS removal, compared to 50% for RC1 and 49% for RM5. However, the microbiological reactors produced higher accumulated biogas volumes (22.74 Nm3 for RM5 and 21.22 Nm3 for RM1) relative to the control reactors (17.33 Nm3 for RC5 and 13.37 Nm3 for RC1). In evaluating the potential use of digestates as biofertilizers, the biodigesters with four-point bottom recirculation (R1 and RM1) exhibited greater stabilization than the digestate from the biodigester with single-point bottom recirculation (R2), displaying lower C/N ratios (0.79 and 1.25 for R1 and RM1, respectively, versus 1.63 for R2) and lower sodium concentrations (0.26 and 0.21 g/Kg for R1 and RM1, respectively, versus 0.30 g/Kg for R2). All evaluated digestates presented micronutrient concentrations below the maximum limits established for biofertilizers and macronutrient values below the reference values stipulated by Brazilian and European legislation. It is

concluded that four-point bottom pumping recirculation proved more efficient than single- point recirculation, that the bioaugmentation strategy with the hydrolytic microbial

consortium was effective for both biogas and biomethane production and organic matter degradation in the biodigesters, and that, generally, all digestates showed potential for use as complementary mineral fertilizer, contributing to the system's circular economy and aiding in environmental sustainability.