Efeito do nutriente e alcalinizante na produção de metano a partir da fração líquida do resíduo de frutas e verduras em um e dois estágios

Abstract

Population growth and the expansion of urban areas have significantly increased energy demand, requiring sustainable solutions that reconcile energy efficiency with environmental preservation. At the same time, the generation of large volumes of organic waste, especially in distribution centers such as the Supply Centers (CEASA), poses a challenge for urban solid waste management. In Ceará, the CEASA unit in Maracanaú discards, on average, 13.7 tons per day of fruit and vegetable waste (FVW), which, due to its high organic load, has potential for biogas production through anaerobic digestion (AD). This biological process, carried out in the absence of oxygen, converts organic matter into methane (CH ) through the action of microbial consortia. Its performance depends on factors such as substrate composition and concentration, hydrogen potential (pH), temperature, hydraulic retention time, and adequate supply of nutrients and alkalizing agents. AD can be conducted in a single-stage or two-stage system, with the latter allowing the separation of the initial phases (hydrolysis and acidogenesis) from the final phases (acetogenesis and methanogenesis) of biological conversion, thus enabling specific control of operational variables in each phase. This study aimed to identify the most effective combination of nutrient medium and alkalizing agent to maximize methane production from the liquid fraction of FVW and subsequently compare the performance of single- and two-stage AD systems. Different combinations of nutritional supplements, including an optimized medium, and alkalizing agents (ammonium bicarbonate, sodium bicarbonate, and calcium carbonate) were tested in batch assays. First, the isolated effects of each additive in both systems were analyzed. Then, the interaction between nutrient media and alkalizing agents was evaluated to determine the most effective conditions for CH production. Results indicated that the two-stage system achieved superior performance (282 mL CH4) compared to the single-stage system (182 mL CH4), representing an increase of approximately 55% in methane production. The most efficient combination was the optimized nutrient medium associated with ammonium bicarbonate, which reached 282 mL CH , the highest yield obtained in the experiments. It was found that AD performance is strongly influenced by the interaction between the chemical and biochemical aspects of the process, making the combined adjustment of alkalinity and nutrient supply essential for optimizing substrate-to-energy conversion. These results reinforce the feasibility of energy recovery from urban organic waste through AD, particularly in higher-performance configurations.