Produção de hidrogênio e metano a partir do POME: avaliação de parâmetros e aumento de escala

Abstract

In Brazil, it is estimated that approximately 1.8 million tons of POME (palm oil mill effluent) are generated annually. This complex effluent is produced in large volumes by the palm oil industry and, due to its high organic matter content, presents significant potential for conversion into bioenergy, particularly in the form of hydrogen (H2) and methane (CH4), thus representing a sustainable alternative for mitigating environmental impacts. This dissertation aimed to evaluate the biological production of H2 and CH4 from POME by assessing operational parameters and larger volume reactors. In the H2 production stage, the effect of thermal pretreatment of anaerobic sludge and the influence of the native microbiota of POME were evaluated. Sludge pretreatment proved essential to maximize H2 production by inhibiting hydrogen-consuming microorganisms and selecting more efficient fermentative populations. Although the microbiota naturally present in POME was also capable of producing H2, its presence did not significantly influence the system’s performance, indicating that POME sterilization is unnecessary. The best H2 production results were obtained after 44 hours of fermentation at 35 °C, with an initial organic load of 40 gCOD/L and pressure release throughout the process, achieving a specific production of 1401 N-mL/L, a yield of 36 N-mL/L·gCOD, and a productivity of 32 N-mL/L·h. Furthermore, experiments conducted at different reactor volumes (300, 600, 1100, and 7000 mL) showed comparable performance, with a linear relationship observed between reactor volume and total H2 production, demonstrating process robustness and scalability potential. For CH4 production, direct anaerobic digestion (from POME) and sequential digestion (from the effluent of the H2 production stage) were compared. The sequential approach showed superior performance, reaching a specific production of 3873 N-mL/L in 35 days, which was 27% higher than that obtained through direct digestion after 63 days. Additionally, the overall energy potential of the sequential process was 62% greater, confirming the advantages of phase separation for improved energy recovery from POME. Although further studies at near-industrial scales are still required, the results demonstrate the technical feasibility of integrated H2 and CH4 production from POME. The proposed approach represents a promising alternative for valorizing this effluent, contributing to energy matrix diversification and the development of more sustainable solutions in the agro-industrial sector.