Codigestão anaeróbia da fração orgânica de resíduos sólidos urbanos com glicerina e estimativa dos potenciais elétrico e térmico

Abstract

The increasing generation of municipal solid waste (MSW) in Brazil, which reached approximately 80.96 million tons in 2023, equivalent to 211 thousand tons per day, represents a significant environmental issue. The improper disposal of these wastes, especially the organic fraction of municipal solid waste (OFMSW), can exacerbate environmental and public health problems. This scenario demands sustainable solutions for its management. OFMSW represents a valuable resource for biogas production through anaerobic digestion, particularly when combined with co-substrates that optimize the process, such as residual glycerin, a byproduct of biodiesel production. This study aimed to evaluate the anaerobic co-digestion of OFMSW with residual glycerin and estimate the electrical and thermal potentials of the produced biogas. Experiments were conducted using 11 anaerobic reactors and 3 control reactors in batch mode, under a controlled temperature of 37±1 °C, for 53 days. The experimental design followed a Central Composite Rotational Design (CCRD), varying the inoculum-to-substrate ratio (ISR) and the percentage of glycerin added to the OFMSW. The best performance was observed in reactor 11, which operated with 3% glycerin and an ISR of 0.4, achieving a cumulative biogas volume of 3.0769 LN, with yields of 353.666 LNbiogas/kgVSadded and 924.678 LNbiogas/kgVSremoved. Analysis of variance (ANOVA) for the response variables—cumulative biogas volume and yield (LNbiogas/kgVSremoved)—showed significant effects at a 95% confidence interval (p<0.05). According to the response surfaces, the glycerin percentage did not exert a significant influence on the reactors, whereas the lowest ISR value resulted in the highest biogas production, being associated with a higher proportion of substrate relative to the inoculum. The optimal condition was established for a mixture of 94.2% OFMSW with 5.8% glycerin and an ISR of 0.4, ensuring higher biogas production and yield. Based on these results and considering a daily generation of 17.16 kg of OFMSW at the university restaurant of UTFPR - Campo Mourão, the estimated energy generation potential was 66.06 kWh/year of electricity and 2,450.90 kcal/day of thermal energy. These findings demonstrate that the anaerobic co-digestion of OFMSW with glycerin can be a sustainable alternative for waste valorization and renewable energy generation.