Produção anaeróbia de ácidos carboxílicos a partir de glicerol residual oriundo de biodiesel

Abstract

Carboxylic acids are acids produced anaerobically during fermentation of organic matter, precursors of methane formation. Among the main acids produced are caproic acid, which has several applications in the chemical industry; valeric acid, biofuel feedstock and heptanoic acid, used in the production of biodiesel, antimicrobials and bioplastics. Glycerol, a by-product produced in large quantities in the production of biodiesel can also be used for various purposes, mainly as raw material in the chemical industry for the generation of biotechnological products. However, with the increased demand for biodiesel imposed by Brazilian legislation, in the future there may be excess glycerol in the environment. Then, in this work, glycerol with ethanol addition was used after the 80th day of operation in an upflow anaerobic sludge blanket reactor (UASB), in order to generate value-added products from the carboxylic chain elongation process. The reactor had a useful volume of 13.8 L, was operated with organic volumetric load of 8 gDQO.L- 1.d-1, pH 5.3 and inoculated with sludge from a Sewage Treatment Plant (ETE) of the Company of Water and Sewerage of Ceará (CAGECE). By high performance liquid chromatography (HPLC) the main products generated were 1,3-PDO, valeric acid and propionic acid, totaling more than 70% of the metabolites produced, even with little variation of the concentration of ethanol added, which can mean in the internal production of propanol by the system and its performance as an electron donor in the process of carboxylic chain elongation. It is believed that glycerol is best suited for odd carboxylic chain elongation.