Digestão anaeróbia do glicerol oriundo da produção do biodiesel: alternativas para geração de energia e produtos de alto valor agregado.

Abstract

The present study aimed to evaluate glycerol from biodiesel as Substrate for synthesis of hydrogen (H2), methane (CH4) and carboxylic acids through Anaerobic digestion. Initially, bench tests were carried out in batch With the purpose of evaluating H2 production by varying the inoculum source (flocculent sludge From sewage treatment plant - ES, granular sludge from Brewery effluent treatment plant - EC, goat ruminal fluid - LR and one Uniform mixture of these inoculants - MX) and the strategy of inhibition of metagenesis - EIM (Addition of chloroform, acid shock and heat shock). After that, the Of the substrate / microorganism ratio (S0 / X0) in H2 production. The values ​​of S0 / X0 Tested ranged from 1 to 16 g of chemical oxygen demand (COD) / g of total solids Volatile compounds (VTS). For the experiments in continuous flow, a system of reactors was used UASB (upflow anaerobic sludge blanket) type, fed with Glycerol to evaluate H2 and CH4 production. In the last step of the research, Conducted batch tests to evaluate glycerol as a substrate to produce Caproic acid (C6), varying the origin of the inoculum, the concentration of ethanol, with and without Bioaumentation with Clostridium acetobutylicum. The results showed that inocula ES, LR and MX, added with chloroform, were the most efficient in selecting the Hydrogen producing bacteria, with yields varying between 0.12 and 0.21 mol H2 / mol glycerol. The S0 / X0 tests showed that the maximum H2 yield (32 mL H2 / gDQA or 35 L H2 / kg glycerol) was achieved when S0 / X0 of 10 gDQO / gSTV. Above this value, the H2 yield decreased, but the production rate Constant (on average 167 mL H2 / [gSTV.d]). The results in flow Showed that the UASB producer of H2 (RH) filled with carrier medium could be Stably operated at 50 kg COD / m3.d and produce 46 L biogas / d, 51% being composed of H2, which was reflected in a yield of 0.135 mol H2 / mol glycerol. The UASB reactor Producer of CH4, fed with diluted RH effluent, was operated with maximum VOC of 19 kg COD / m3.d and was able to produce 92 L biogas / d, 74% composed of CH4, Resulting in a methane-specific production of 0.25 m 3 CH 4 / kg COD added. In In terms of energy, H2 and CH4 produced by UASB reactors are capable of 171 MJ / m3 reactor. Based on the maximum concentrations of 1,3-propanediol, And caproic acid produced in laboratory scale, it was possible to estimate that A plant that generates 25 m3 glycerol / d can achieve a daily profitability between US $ 1,848.43 and 6,765.07, depending on the desired product. Finally, the production tests of C6 allowed to conclude that the highest concentration (3.8 g C6 / L) was found when sludge Granular from brewery effluent treatment plant was bioaumented, With addition of 100 mM ethanol.