Produção de hidrogênio e metano em processo sequencial utilizando o preparado enzimático sólido residual (PESR)

Abstract

The production of biocatalysts by Solid-State Fermentation (SSF) from the residual biomass of the oil industry has been investigated in order to reduce the costs of enzymatic production of biodiesel. The culture medium with lipase after SSF can be used entirely as a lipase-active biocatalyst called Dry Fermented Solid (DFS). DFS has been studied as a biocatalyst for biodiesel production from the reaction between Palm Fatty Acid Distillate (PFAD) and ethanol. In this process, after the production of 1L of biodiesel, about 350g of Residual Dry Fermented Solid (RDFS) is generated. RDFS is a waste rich in organic matter, which makes it attractive for the biological production of H2 via fermentation and CH4production via anaerobic digestion in a sequential process. Thus, the use of RDFS is interesting because it adds value to this residue from biodiesel production, besides producing clean and decentralized energy. Thus, the objective of this work was to evaluate the production of H2 and CH4 in a sequential process using RDFS, derived from biodiesel production, and as inoculum, an anaerobic sludge from the biodigester of a sewage treatment plant located in Rio de Janeiro city. For H2 production, sludge was heat-treated (HT) at 65°C for 30 minutes, and CH4 production, sludge was used without pretreatment (WP). Fermentation was conducted in a 100 mL penicillin flask with a working volume of 45 mL. The medium had the initial pH adjusted to 5.5 and was purged with N2 for 45 s to be incubated at 150 rpm and 35 ° C for 24 h. Digestion followed the same procedure, with the initial pH adjusted to 7.0. Analysis of oils and greases indicated that 60 ± 3% of the mass of RDFS is made up of oils and greases. The complete characterization of RDFS by the adapted NREL’s method indicated that 71% of the mass is extracted material, 17% of sugars being the main mannose, 10% of insoluble solids in H2SO4 and 2% of ash. For H2 production, four RDFS concentrations were evaluated, 15; 23; 31 and 46 gRDFS / L at 24 h, and a kinetics study was also carried out. The best H2 yield was obtained at 24h with a concentration of 31 gRDFS / L resulting in 172 ± 32 mLH2 /L gRDFS. In the sequential production of CH4, the best yield was 35 days (214 ± 1 mLCH4/gCOD), which represented 61% efficiency. The results show that RDFS is a residue with potential for the production of biogas, consisting mainly of fatty acids that serve as a carbon source for microorganisms.