Avaliação das características físico-químicas do efluente da agroindústria da mandioca e do seu potencial bioenergético

Abstract

Cassava is a widely consumed food throughout the Brazilian territory, it is used in basic food, in elaborate dishes and for animal sustenance as a herd fattening. The industrial processing of cassava allows the production of various foods (for example, flour and starch), but generates liquid residues, which have a high polluting potential. This work aims to carry out a bibliographical survey of the characteristics of wastewater from cassava processing generated in Brazil, one of the main producers of this crop, to suggest more adequate processes to treat them and obtain predictive models that facilitate their characterization. There was a high concentration of organic matter, nutrients, solids, and cyanide in this type of effluent, which has been evaluated as an alternative raw material for obtaining biofuels, fertilizers, pesticides and others. In general, it was found that the effluents from the production of flour (manipueira) have a higher concentration of pollutants than the effluents from the starch extraction, as the second process uses more water, diluting the effluent. An excellent linear correlation was obtained between the parameters COD and BOD 5 (R2 > 0.8),suggesting that the BOD 5 value can be estimated from the COD for these effluents. The average BOD 5 /COD ratios for flour production (0.49) and for starch extraction effluents (0.47) indicate high biodegradability of the effluents. In addition, when analyzing the relationship between organic matter and nutrient concentrations (C:N:P), it was found that anaerobic biological processes are more suitable to treat them, being evidenced by the common use of stabilization ponds and biodigesters in Brazil. Since this effluent is rich in carbohydrates and nutrients, a survey was also carried out on the production of bioethanol, biobutanol and biohydrogen, in addition to biogas. Bio-hydrogen has been obtained through fermentative or phototrophic processes, and in most works the yields were considered good, reaching 48%. Bioethanol has been obtained through prior hydrolysis of starch followed by fermentation and yields of up to 100% can be observed. Biobutanol production by acetobutanolic fermentation allowed toobtain similar ethanol yields. For biogas, the maximum yield can reach 81.41% in methane. These results suggest that effluents from industrial processing of cassava can serve as raw material to produce of biofuels.