Biorefinery applied to the management of coffee processing residues co-digested in industrial wastes for the generation of biogas

Abstract

In Brazil, public policies to encourage and support investments in biogas systems make production from industrial waste feasible. Surplus residues from coffee processing, such as wastewater and solid residues (pulp and husk), as well as residues from the brewing industry's production chain are generated annually, with inappropriate disposal causing environmental impact. The ability to reuse these residues is notorious since they are considered excellent substrates for anaerobic digestion. The proposal presented is unprecedented, since two wastewater and solid residues will be associated in codigestion in a fermentative-methanogenic system to obtain organic acids and biogas. In addition, the use of a mixed consortium composed of cattle manure and granular sludge of UASB reactor will increase the potential for energy recovery of the substrates to be treated. For this purpose, batch assays will be carried out in order to evaluate the ideal proportions of wastewater from coffee and brewery processing, of solid pulp and coffee residues, in addition to the presence of yeast extract in anaerobic codigestion, by Central Composite Rotational Design (CCRD) for CH4 generation. For this purpose, the following will be tested: concentration of yeast extract (0, 1 to 2 g L-1), concentration of wastewater from coffee processing (10, 15 and 20 g COD L-1), concentration of pulp and husk pre-treated (3.5, 7 and 10.5 g L-1) and concentration of the brewery's wastewater (1.5, 2 and 2.5 g COD L-1). Continuous EGSB reactor will also be evaluated from the conditions previously defined, in 48, 36, 24 and 18 h HRT. All assays will be monitored for the generation of biogas, carbohydrates and organic acids. With this possibility, it is expected to obtain degradation of solid and liquid residues in anaerobic co-digestion, as well as the generation of CH4 through the application of continuous EGSB reactor. This possibility provides a realistic view of the management of these wastewater and solid waste. It is also intended to contribute to the taxonomic and functional characterization of bacteria and archaea for the different operational conditions of batch and continuous reactors. (AU)