Produção de hidrogênio e metano a patir de glicerol bruto e cultura mista em reatores anaeróbios de leito fluidizado termofílicos

Abstract

The study aimed to evaluate the continuous production of hydrogen and methane under thermophilic conditions (55 °C) using crude glycerol as substrate and mixed culture. The first study aimed at the production of H2, and therefore, an acidogenic anaerobic fluidized bed reactor (AFBR) called RA was operated under hydraulic retention time (HRT) variation between 8 and 0.5 h while the affluent glycerol concentration was fixed in 10.0 g L-1. The results showed that the maximum content, 78.5% and H2 volumetric productivity, 1.46 L h-1 L-1, were reached in HRT of 0.5 h. The maximum H2 yield value of was 1.28 mol H2 mol-1 glycerolconsumed, reached in HRT of 1 h. The main metabolites related to high H2 production were butyric acid and butanol, but there was a high production of 1,3-propanediol in the HRT of 6 h, reaching maximum yield of 0.80 mol 1,3-PDO mol-1 glycerolconsumed. The second study, in turn, consisted in evaluating the influence of the adaptation strategy adopted in the operation of two methanogenic AFBR, RM1 e RM2. The RM1 was operated under affluent glycerol concentration variation between 1.0 and 7.0 g L-1, while HRT was fixed in 24 h and the applied organic loading rate (OLR’) variation between 1.0 and 7.0 kg COD m-3 d-1. The maximum content, 86.2% and CH4 yield, 0.47 m3 CH4 kg-1 CODapplied, were reached in the OLR’ of 1.0 and 3.0 kg COD m-3 d-1, respectively. The maximum CH4 volumetric productivity, 4.27 L d-1 L-1, was reached in the OLR’ of 7.0 kg COD m-3 d-1. At RM2 the HRT ranged from 36 to 6 h while the affluent glycerol concentration was set at 10.0 g L-1 and the OLR’ variation between 6.7 and 40.0 kg COD m-3 d-1. It was observed that the application of high TCO’ in an unadapted reactor, was shown degenerative to the production of CH4, due to the accumulation of volatile acids in the system. Thus, it can be inferred that crude glycerol, the main by-product of biodiesel biorefineries, can be used in the production of bioenergy (H2 and CH4) and valueadded metabolites, valuing the productive chain of this biofuel.