Avaliação do crescimento microalgal sob diferentes condições de cultivo utilizando a vinhaça como matéria-prima: análise de crescimento e potencial biorremediador a partir da recuperação de nutrientes

Abstract

With the growing concern about environmental problems, especially in relation to carbon gas emissions, one of the alternatives to minimize negative environmental impacts may be the replacement of fossil fossils by biofuels. As a result, the sugar and alcohol sector has been standing out due to the possibility of producing ethanol from sugarcane, and Brazil has been standing out for being one of the main ethanol producers in the world. However, in any process of transforming sugarcane into ethanol, approximately 13 L of vinasse is generated for every 1 L of alcohol produced. The characteristics of the vinasse can vary according to the species of sugarcane and the maturation process, but in general it has a high concentration of nutrients such as nitrogen and potassium, which is why they are often used for fertigation in sugarcane crops -of sugar. However, frequent application to the soil or incorrect disposal of this residue can be harmful to the environment, as characteristics such as high concentration of organic matter, low pH, high corrosivity, in addition to the presence of nutrients such as nitrogen, phosphorus, potassium and phenolic compounds can cause environmental contamination. Therefore, several studies seek solutions for treating vinasse, and one of the promising alternatives may be the cultivation of microalgae, as they present, in addition to their bioremediation capacity, a possibility of using microalgal biomass for biofuel production. Thus, this study evaluated the cultivation of microalgae under different growth conditions using vinasse as a raw material, in order to identify the best culture conditions. For this purpose, cultures and dilutions were carried out both in distilled water and in BG11 medium. Thus, the objective was to verify the influence of vinasse on the growth of microalgae in a medium with nutrient enrichment (BG11) and another medium without enrichment (distilled water), in addition to determining the potential for bioremediation of vinasse from the cultivation of microalgae. Considering that microalgae act as a bioremediator, its application can be viable as a tertiary effluent treatment process, when used mainly with dilution and pH correction, factors that can help to improve productivity. The results show that cultivation with 100% vinasse and 50% vinasse (BG11 and distilled water) does not feed cell growth rate. Cultivation with 10% vinasse in BG11 showed better growth (μ max = 0.48 d-1) compared to cultivation with distilled water (μ max = 0.23 d-1). Cultivations with 10% vinasse (BG11 and distilled water) and control showed 100% efficiency in removal of N-NH4+ and P, which demonstrates the possibility of using microalgae for bioremediation of vinasse. However, specifically for nitrogen, it was found that the main removal mechanism was volatilization, with no considerable recovery of the nutrient in the form of biomass.