Anaerobic digestion of vinasse improves its use as a liquid fertilizer

Abstract

The global demand for exploiting the potential of renewable biofuel production is increasing. When countries with large agricultural areas produce ethanol, they also generate a harmful byproduct called vinasse. Vinasse is a dark brown effluent that contains a high amount of organic matter, has an acidic nature, and is rich in mineral salts. Managing this effluent poses a challenge due to its significant volume, which ranges from 8 to 20 liters per liter of ethanol produced. Traditionally, raw vinasse has been applied directly to the soil as a liquid fertilizer. However, this practice, without proper guidance, can lead to soil degradation, micronutrient imbalance, pH change and excessive accumulation of organic matter. To resolve these issues and still use vinasse as a fertilizer, the process of anaerobic degradation of vinasse in biodigesters was analyzed. The resulting treated effluent, known as digested vinasse, was then compared to raw vinasse in terms of pollution parameters and the balance of minerals crucial for sugarcane cultivation. The results demonstrated a significant reduction in the organic load of vinasse, with a removal of chemical oxygen demand (COD) ranging from 66% to 85%. After applying the digested vinasse to sugarcane like cultivation soil, a noticeable decrease in the environmental impact caused by excessive organic matter was observed. Additionally, the study found that important nutritional elements such as sodium (Na) did not have any adverse effects or accumulate excessively when compared to calcium (Ca) and magnesium (Mg). In conclusion, the research demonstrates that the anaerobic degradation of vinasse in biodigesters can effectively reduce its organic load and mitigate the environmental impact associated with the direct application of raw vinasse to agricultural soils