Influência da carga orgânica na produção de biogás em reator anaeróbio de bancada

Abstract

Rising global energy demand and the need to reduce greenhouse gas emissions have driven the use of residual biomass as a renewable alternative. The anaerobic co-digestion of agroindustrial waste offers potential for biogas and biofertilizer production, contributing to circular economy principles. This study compared the kinetic behavior of biogas production at two total solids concentrations (4% and 8% TS). Substrates were characterized via total solids (TS) and volatile solids (VS) analyses. Tests were conducted in bench-scale reactors (2 L PET bottles) under mesophilic conditions (30–40°C). Biogas production was monitored using the liquid displacement method over 31 days. Data were fitted to the Modified Gompertz model using non-linear regression (least squares) to determine the biogas production potential (A), maximum biogas production rate (Kz), and lag phase (λ); fit quality was evaluated using R² and root mean square error (RMSE). The low-load experiment yielded 893 mL of cumulative biogas, with a specific yield of 31.85 mL/gVS, while the medium-load experiment reached 1481 mL with 26.41 mL/gVS. The Modified Gompertz model showed a high degree of fit to the experimental data (R² of 0.9817 and 0.9898, respectively), with kinetic parameters indicating a higher maximum production rate under the 4% TS condition (Kz = 102.9) and a shorter lag phase (λ = 1.4 days) compared to the 8% TS condition (Kz = 68.5; λ = 8.35 days). The results demonstrated that the lower total solids concentration favored specific organic conversion efficiency and production kinetics, suggesting diffusional limitations associated with the increase in organic load.