Enhancing biogas production from vinasse in sugarcane biorefineries: Effects of urea and trace elements supplementation on process performance and stability

In this study, the effects of nitrogen, phosphate and trace elements supplementation were investigated in a semi-continuously operated upflow anaerobic sludge blanket system to enhance process stability and biogas production from sugarcane vinasse. Phosphate in form of KH2PO4 induced volatile fatty acids accumulation possibly due to potassium inhibition of the methanogenesis. Although nitrogen in form of urea increased the reactor's alkalinity, the process was overloaded with an organic loading rate of 6.1 g COD L−1 d−1 and a hydraulic retention time of 3.6 days. However, by supplementing urea and trace elements a stable operation even at an organic loading rate of 9.6 g COD L−1 d−1 and a hydraulic retention time of 2.5 days was possible, resulting in 79% higher methane production rate with a stable specific methane production of 239 mL g COD−1.